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1
Content available Dielectric properties of ferroelectric liquid crystalline material with chiral nematic phase
Wojciechowski M., Bąk G. W., Tykarska M.
Scientific Bulletin. Physics / Lodz University of Technology
|
2015
|
Vol. 36
77--86
EN
The ferroelectric liquid crystal with nematic N* phase has been investigated using broadband low frequency dielectric spectroscopy. The dielectric relaxation modes related to a ferroelectric Goldstone mode were detected only in a narrow temperature range. Well defined relaxation process was detected in the SmB* phase at about 90 Hz.
PL
Dielektryczne badania ferroelektycznego związku ciekłokrystalicznego 1H3R z nematyczną fazą chiralną przeprowadzono w obszarze niskich częstości. Procesy relaksacyjne zarejestrowano jedynie w fazie ferroelektrycznej (mode Goldstona) oraz w fazie SmB* w obszarze częstości 60÷90 Hz. Przedstawiono charakterystyki zarejestrowanych procesów relaksacyjnych.
2
Content available Technology and properties PMN-PT-PS-PFN:LI material for multilayer capacitor
Niemiec P., Skulski R., Bochenek D., Wawrzała P.
Archives of Metallurgy and Materials
|
2013
|
Vol. 58, iss. 4
1313--1316
EN
In this work it is designed and obtained the multicomponent material with the formula 0.6075PMN-0.2025PT-0.09PS- 0.1PFN:Li (PMN-PT-PS-PFN:Li) for applications in multilayer ceramic capacitors MLCC. Obtaining of PMN-PT-PS-PFN:Li was done by two alternative methods of synthesis. In the first method a PMN-PT-PS-PFN:Li has been obtained from simple compounds (oxides, carbonates), in the second method the complex compounds (MgNb2O6 and FeNbO4) and simple compounds (oxides PbO, TiO2 and carbonate Li2CO3) were used. From synthesized powder of PMN-PT-PS-PFN:Li the ceramic samples were obtained which have next undergone comprehensive investigations. The X-ray investigations, as well as ferroelectric, dielectric and elastic investigations have been made.
PL
W pracy zaprojektowano i otrzymano wieloskładnikowy materiał o wzorze 0.6075PMN-0.2025PT-0.09PS-0.1PFN:Li (PMN-PT-PS-PFN:Li) dla zastosowań na podłoża do wielowarstwowych kondensatorów MLCC. Otrzymywanie materiału PMN-PT-PS-PFN:Li było prowadzone dwiema metodami syntetyzowania. W pierwszej metodzie do otrzymania PMN-PT-PS- PFN:Li zastosowano syntetyzowanie prostych związków (tlenki, węglany), w drugiej metodzie zastosowano syntetyzowanie złożonych związków (MgNb2O6 i FeNbO4), oraz prostych związków (tlenków PbO, TiO2 i węglanu Li2CO3). Z syntetyzowanego proszku materiału PMN-PT-PS-PFN:Li otrzymano ceramiczne próbki które zostały poddane kompleksowym badaniom. Przeprowadzono badania rentgenowskie, mikrostrukturalne oraz ferroelektrycznych, dielektrycznych i sprężystych właściwości.
3
Content available remote Diffuse phase transition of polycrystalline (Ba0.9Sr0.1)TiO3
Kajtoch C., Gabryś M., Bąk W., Starzyk F.
Materiały Ceramiczne
|
2010
|
T. 62, nr 3
400-402
PL
Przedstawiono wyniki pomiarów rentgenowskich (XRD) i dielektrycznych dla polikrystalicznego (Ba0,9Sr0,1)TiO3 (BS10T). Wyniki pomiarów pokazują obecność, w temperaturze 373 K, rozmytej przemiany fazowej (DPT) pomiędzy strukturą regularną i tetragonalną. Temperatura maksimum rzeczywistej składowej przenikalności elektrycznej (ε') nie zależy od częstotliwości elektrycznego pola pomiarowego. Kąt fazowy, Φ ≈-90°, między prądem a przyłożonym napięciem elektrycznym sugeruje występowanie obszarów polarnych (klasterów) poniżej 400 K, tj. w obszarze temperaturowym DPT i w fazie paraelektrycznej.
EN
The results of X-ray diffraction (XRD) and dielectric measurements performed for polycrystalline (Ba0.9Sr0.1)TiO3 (BS10T) are presented. Data from these measurements show a presence of diffuse phase transition (DPT) between cubic and tetragonal structure at a temperature of 373 K. The temperature Tm of the maximum of real part permittivity (ε') does not depend on the frequency of the applied electric field. A phase angle, Φ ≈ -90° between current and applied voltage, suggests an occurrence of polar regions (clusters) below 400 K i.e. in the DPT temperature range of and in the paraelectric phase.
4
Dielectric properties of polycrystalline Ba0.36Na0.64Ti0.36Nb0.64O3
Bąk W.
Inżynieria Materiałowa
|
2010
|
Vol. 31, nr 6
1415-1417
EN
Polycrystalline samples of Ba0,36Na0,64Ti0,36Nb0,64O3 (BNTN64) solid solution were obtained with conventional method and subjected to dielectric properties studies. The measurements were made with application of dielectric spectroscopy technique at the frequencies ranging from 20 Hz to 1 MHz and the temperature above 123 K and below 473 K. The temperature and frequency dependencies of real (??) and imaginary (??) parts of the dielectric permittivity confirm a presence of ferroelectric diffuse phase transition in BNTN64. The parameters describing the phase transition and occurring in the Curie-Weiss law were calculated. It has been also shown that thermal activation energy of AC electric conductivity (at 20 Hz) assumes a value typical for semiconductors.
PL
Polikrystaliczne próbki roztworu stałego Ba0,36Na0,64Ti0,36Nb0,64O3 (BNTN64) otrzymano metodą kalcynacji/konwencjonalną. Badania właściwości dielektrycznych wykonano metodą spektroskopii dielektrycznej w zakresie temperatury od 153 K do 473 K oraz w zakresie częstotliwości 20 Hz÷1 MHz. Analiza temperaturowych i częstotliwościowych zależności rzeczywistej (??) i urojonej (??) części przenikalności dielektrycznej wskazuje na rozmytą przemianę fazową. Parametry przejścia fazowego materiału opisano za pomocą uogólnionego prawa Curie-Weissa, uwzględniającego stopień rozmycia przemiany. Wartość cieplnej energii aktywacji przewodnictwa przemiennoprądowego (dla 20 Hz) jest typowa dla półprzewodników.
5
Content available remote Ferroelektryki w szkłach porowatych
Rysiakiewicz-Pasek E., Poprawski R.
Szkło i Ceramika
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2009
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R. 60, nr 6
4-7
PL
W pracy przedstawiono metody wprowadzania wybranych materiałów ferroelektrycznych (TGS, NaN02 oraz KN03) w matryce szkieł porowatych o różnych średnich rozmiarach porów. Na podstawie pomiarów właściwości elektrycznych (piroelektrycznych i przenikalności elektrycznej) oraz termicznych (rozszerzalności termicznej i ciepła właściwego) stwierdzono, że w otrzymanych kompozytach sekwencje przemian fazowych są takie same jak w kryształach litych. Wykazano, że temperatury przemian fazowych zależą od rozmiarów porów.
EN
The methods of introducing of selected ferreoelectrics materials (TGS, NaN02 and KN03) into porous glasses matrix with different pores size were presented. On the basic on measurements of electrical (pyroelectric, dielectric permittivity) and thermal (thermal expansion, specific heat) properties it was stated that sequence of phase transitions are similar to those in bulk crystals. It was shown that the temperature of phase transitions depends on pore dimensions.
6
Content available remote Study of the relaxor behaviour in Ba0.68Na0.32Ti0.68Nb0.32O3 ceramic
Bąk W.
Journal of Achievements in Materials and Manufacturing Engineering
|
2009
|
Vol. 37, nr 1
24-27
EN
Purpose: The purpose of this work was to synthesize a new ceramic solid solution Ba0.68Na0.32Ti0.68Nb0.32O3 (BNTN32), as well as to measure and analyse its dielectric properties within the temperature range 123 K-473 K, where dielectrically active phase transition was supposed to occur. Design/methodology/approach: The new ceramic composition was prepared by means of conventional method. Dependence of phase transition features on temperature and frequency of measuring field were measured using dielectric spectroscopy method within the frequency range from 20 Hz to 1 MHz. Findings: The electric susceptibility along with temperature decrease generally rises up and has transient dispersion vanishing at about 230 K. At higher and low temperatures, frequency dependence of dispersion differs in character: at temperatures at ~400 K, low frequency values dominate. Dielectric energy losses are very high at ~high temperature, they decline down while temperature decrease, and at about 200 K range its frequency dependence is reversed and less scattered with maximum at ~150 K. The whole transition of ferroelectric - paraelectric (FE - PE) type can be described by means of Curie-Weiss law and it gets diffused character. Research limitations/implications: For modelling purposes the structure parameters of BNTN32 have to be measured by X-ray diffraction in order to establish the dielectric/structural activities of transitions taking place within used the temperature range. Additionally, dielectric measurements within broader frequency range up to 1.8 GHz will be performed. Originality/value: The new type of ceramic material was prepared with interesting dielectric properties. Dispersion reverse of energy losses activated thermally and low frequency memory of barium titanate (BT) transition effect visible at ~400 K is to be a subject of modelling further work.
7
Content available remote Relaxor phase transition of polycrystalline (Ba0.90Sr0.10)(Ti0.75Sn0.25)O3
Kajtoch C.
Journal of Achievements in Materials and Manufacturing Engineering
|
2009
|
Vol. 37, nr 1
44-47
EN
Purpose: The purpose of this work was to determinate the influence of the nonferroactive 25% Sn substitutions in (sublattice B) on changes of the character of phase transition (PT) in comparison with pure barium titanate BaTiO3 (BT). Design/methodology/approach: The dielectrometry method was applied in order to measure complex dielectric permittivity and other dielectric functions of ferroelectric (Ba0.90Sr0.10)(Ti0.75Sn0.25)O3 (BSr10TSn25). Findings: It was affirmed, that 25% substitution of Sn ions changed the type of phase transition. The transition was strongly diffused and typical for relaxor materials. The strong dependence of temperature Tm (peak of the electric permittivity ĺ’) on frequency of the applied electric field was observed. It means, that this material belongs to relaxor type. The polar character of this solution was also observed in a broad temperature range (in the paraelectric phase too). This behaviour is connected with the occurrence of polar regions (clusters). Practical implications: The results can be used in order to describe changes of PT in the relaxor solid solutions with nonferroactive substitutions in sublattice B. Originality/value: Value of this work relies on the experimental examination of the dielectric properties of (BSr10TSn25) solid solution. The temperature of the glassy transition Tf and the activation energy was calculated. The low value of the phase angle is connected with the existence of the polar regions. The dielectric phase transition is connected with change of interactions, of average range, in the system of clusters.
8
Content available remote Studies of electrical transport in barium titanate single crystal
Osak A.
Czasopismo Techniczne. Nauki Podstawowe
|
2009
|
R. 106, z. 1-NP
109-121
EN
Results of the studies on electrical transport and related relaxation phenomena in ferroelectric BaTiO[3] single crystal are presented. Investigations of polarisation and depolarisation in the samples show an existence of very slow relaxation currents in the material. In the neighbourhood of Curie temperature the relation J [tilde] V[^6/5] is fulfilled. The energy activation calculated from depolarisation currents and electrical conductivity are the same and equal to 0.42eV.
PL
W artykule zostały przedstawione wyniki badań nad przewodnictwem elektrycznym i mechanizmem relaksacji w ferroelektrycznym monokrysztale BaTiO[3]. Badania polaryzacji i depolaryzacji w tym materiale wskazują na występowanie bardzo wolnych prądów relaksacji. W pobliżu punktu Curie spełniony jest związek J [tylda] V[^6/5]. Energie aktywacji wyznaczone z prądów depolaryzacji i przewodnictwa elektrycznego są takie same i równe 0,42eV.
9
Content available remote The dielectric behaviour of polycrystalline Ba0.96Na0.04Ti0.96Nb0.04O3 solid solution
Bąk W., Gabryś M., Kajtoch C., Tejchman W., Starzyk F.
Archives of Materials Science and Engineering
|
2009
|
Vol. 40, nr 1
13-16
EN
Purpose: The purpose of this work was to measure and investigate dielectric properties of new material, polycrystalline solid solution Ba0.96Na0.04Ti0.96Nb0.04O3 (BNTN4) within the temperature range 153 K-473 K. Design/methodology/approach: The dielectric spectroscopy method has been applied to measure dielectric and electric parameters within the frequencies from 20 Hz to 1 MHz. Findings: The dielectric permittivity (&epsilon') dependence on temperature (T) within the range of 473 K-225 K consist of two components: the reversly proportional one and the second one in the form of small local, transient peak at about 400 K. The global maximum is frequency dependent and above &sim 400 K along the T decrease, the dispersion of &epsilon' is initiated and low frequency dispersion of &epsilon' prevails below 250 K. Energy losses measure (&epsilon"), correlated with &epsilon'(T), is generally shifted towards lower T values. Its frequency dependence undergoes inversion which develops with T decrease and is initiated at about 370 K. The whole temperature induced phase transition turned out to be of relaxor kind and diffused process. The detailed analysis of this transition and its features was performed. Research limitations/implications: In order to determine the details of polycrystalline structure of BNTN4 new material for modelling of ferroelectric properties the precise X-ray diffraction measurements should be performed as function of T. The nature of ferroelectric - paraelectric (FE - PE) transition diffusive character will be studied by means of dielectric measurements within frequency range 1 MHz-1.8 GHz. Originality/value: The new kind of ferroelectric solid solution (BNTN4) was synthesized. The specific features of this material at low T range involves among others, the T-dependent dispersion of dielectric properties on low T side of broad &epsilon'(T) peak.
10
Content available remote Structure and AC conductivity of polycrystalline Pb(Cd1/3Nb2/3)O3
Bąk W., Kajtoch C., Mroczka K., Wójcik K.
Archives of Materials Science and Engineering
|
2008
|
Vol. 33, nr 2
75-78
EN
Purpose: Purpose of this work was to determine crystalline structure and ac electric conductivity of polycrystalline sample Pb(Cd1/3Nb2/3)O3 (PCN) in paraelectric phase. Controversies involving uncertainties of phase transition character were the motivation of our experimental investigation: roentgenostructural, electron microscopy (SEM) and dielectric (ε') as well as electric (δ') spectroscopy. Design/methodology/approach: Polycrystalline PCN samples were prepared using hot pressing method. X-ray measurements had been performed with use of DRON3 apparatus (Cu Kα, monochromator: monocrystal LiF, at detector NaI side) with jump of 2O angle accounting for 0.02deg within a range 10-120deg. Structure images were made at room temperature with a use of electron microscope Philips SEM 525M. Dielectric measurements were made with a use of automatic measuring system Quatro Cryosystem 4.0 and Agilent Precision LCR meter HP4284A equipped with WinDETA 5.62 software Novocontrol. Before measurements, polycrystalline PCN samples were refreshed by annealing at 700 K. Next, electric measurements were carried out under cooling with 2 K/min speed. Findings: It was established that cubic phase is present within the whole range of temperatures (173 K-723 K) applied in our measurements. The polar component of the electric conductivity was dominate below the Tm temperature (Tm - temperature at which the maximal value of dielectric permittivity takes place). Above this temperature, activation energy (φ) is falling down, along increasing frequency of measuring field. Research limitations/implications: Changes of AC conductivity of PCN were interpreted in terms of polar regions properties evolution. Originality/value: Results obtained have broad the knowledge about phase transitions occurring without crystal structure change, but involving freezing of polar regions under cooling.
11
Content available remote Structural and dielectric properties of polycrystalline (Ba0.9Sr0.1)TiO3
Kajtoch C., Gabryś M., Tejchman W., Handke B.
Archives of Materials Science and Engineering
|
2008
|
Vol. 33, nr 2
89-92
EN
Purpose: This work is aimed to determination of the influence of Sr - ferroactive substitution on physical properties and character of phase transitions (PT) in barium titanate BaTiO3 (BT). Design/methodology/approach: Polycrystalline samples of BST-10 were prepared by means of calcination method at the 1600 K. Roentgenogram of BST-10 was made within the angles from 10 deg to 110 deg with the 0.008 deg step. Images of the morphology of the samples were taken by means of electron microscope Philips SEM 525M at room temperature. Dielectric measurements were performed with application of Quatro Cryosystem 4.0 and Agilent Precision LCR meter HP4284A equipped with WinDETA 5.62 software Novocontrol. Measurement were taken under cooling with 2 K/min speed. Measuring electric field frequency was from the range 20 Hz-1 MHz. Findings: Dielectric spectroscopy in the frequency domain was applied to measure complex dielectric permittivity and other dielectric functions of ferroelectric polycrystalline (Ba0.9Sr0.1)TiO3 (BST-10). It was established that 10% substitution of Sr in BST-10 solid solution did not change the character of the phase transitions. The temperatures of the phase transitions were correlated with low temperature of PT in SrTiO3 (ST). Similar properties of Ba and Sr ions were taken into consideration. The dipolar character of solid solution was also observed in paraelectric phase. Practical implications: Obtained results can be used to model the effects of ferroactive and nonferroactive substitutions in the A and B subnets of perovskite ferroelectrics. Originality/value: An attempt to correlate low phase angle values observed in the paraelectric phase of BTS-10 with high dielectric permittivity and the occurrence of polar regions.
12
Content available remote Evolution of electric polarization in paraelectric phase of BaTiO3
Bąk W., Kajtoch C., Starzyk F., Żmija J.
Archives of Materials Science and Engineering
|
2008
|
Vol. 33, nr 2
79-82
EN
Purpose: The aim of this work has been to study electric properties of polycrystalline BaTiO3 (BT) at paraelectric phase. On the basis of the obtained results mechanism of dipolar polarization has been discussed. Design/methodology/approach: Polycrystalline samples of barium titanate were prepared using calcinations method, at the temperature about 1670 K. Dielectric measurements were carried out by means of Quatro Cryosystem 4.0 and Agilent Precision LCR meter HP4284A equipped with WinDETA 5.62 software Novocontrol. The samples were refreshed before measurements by annealing at 700 K. The dielectric measurements were carried out within the frequency range 20 Hz - 1 MHz under cooling with 2 K/min speed. Findings: The results show occurrence of maxims of dielectric permittivity (ε') and phase angle (Φ) within the "cross – over" region. The temperatures related to these maxims depend on the frequency of electric field and are higher for higher frequencies. A positive temperature coefficient (PTC) of conductivity has been found in paraelectric phase of BT. Research limitations/implications: It has been postulated, on the basis of the obtained results, that at the temperatures above 400 K (paraelectric phase) two types of polarization exist in BT: the polarization due to free dipoles (Pf) and the polarization (Pd) related to polar clusters formed by the dipoles. Originality/value: The results confirm existence of two types of polarization in paraelectric phase of BaTiO3.
13
Content available remote Ferroelektromagnetyczne jednofazowe materiały inteligentne
Surowiak Z., Bochenek D.
Materiały Ceramiczne
|
2007
|
R. 59, nr 4
128-142
PL
W artykule przedstawiono stan badań ceramicznych materiałów ferroelektromagnetycznych. Materiały te są równocześnie ferroelektrykami (antyferroelektrykami / ferrielektrykami) i ferromagnetykami (antyferromagnetykami / ferrimagnetykami) i jako takie należą do rodziny multiferroikowych materiałów inteligentnych. Są nimi niektóre związki chemiczne i roztwory stałe o różnych typach struktury krystalicznej, w tym: perowskity, bizmutowe tlenki o warstwowej strukturze, boracyty, heksagonalne manganity typu RMnO3, heksagonalne fluoryty typu Ba-MeF4 oraz niektóre związki o strukturze heksagonalnego BaTiO3. W wyniku sprzężenia elektrycznie i magnetycznie uporządkowanych podukładów ferroelektromagnetyki wykazują efekt magnetoelektryczny. Oznacza to, że ich spontaniczna polaryzacja i spontaniczne namagnesowanie mogą być zmieniane zarówno zewnętrznym polem elektrycznym jak i magnetycznym. Liczne zastosowania ferroelektromagnetyków obejmują różnego rodzaju sensory i przetworniki z magnetycznie modulowaną piezoelektrycznością i elektrycznie modulowaną magnetostrykcją.
EN
A review of the most important investigations of the ceramic ferroelectromagnetic materials are presented in this paper. Materials these are ferroelectrics (antiferroelectrics / ferrielectrics) and ferromagnetics (antiferromagnetics /ferrimagnetics) simultaneously and so they belong to family of the multiferroic smart materials. They belong to them some single-phase chemical compounds and solid state solutions with different types of structures, it in this: perovskites, bismuth layered structure oxides, boracites, hexagonal manganites of RMnO3 - type, hexagonal fluorites of BaMeF4 - type and certain compounds of hexagonal BaTiO3 - type. In result of magnetically and electrically ordered systems coupling, these materials can shows magnetoelectric effect. This determines that their spontaneous polarization and spontaneous magnetization may by modified by applying an external electric or magnetic fields. Specific device applications of ferroelectromagnetics include multiple state memory devices, sensors and transducers with magnetically modulated piezoelectricity or electrically modulated magnetostriction.
14
Ferroikowe materiały inteligentne
Surowiak Z., Bochenek D.
Elektronika : konstrukcje, technologie, zastosowania
|
2007
|
Vol. 48, nr 6
50-60
PL
W artykule przedstawiono ogólną charakterystykę materiałów ferroikowych (kryształy, ceramika). Nazwą materiały ferroikowe obejmuje się materiały ferromagnetyczne (FM), ferroelektryczne (FE) i ferroelastyczne (FES). Te trzy rodzaje materiałów nazywane są podstawowymi ferroikami. Mechanicznym lub elastycznym analogiem ferromagnetyzmu i ferroelektryczności jest ferroelastyczność. Materiały wykazujące jednocześnie właściwości ferroelektryczne (FE) i ferroelastyczne (FES) nazywane są ferroelastoelektrykami (FE+FES=FESE). Ferroiki (FE, FM, FES) i ferroelastoelektryki (FESE) należą do rodziny materiałów inteligentnych. Są one defi niowane jako materiały, które mogą być zmieniane i kontrolowane przez zewnętrzne bodźce (magnetyczne, elektryczne, mechaniczne, cieplne). Materiały inteligentne mogą znaleźć zastosowanie w różnych dziedzinach techniki (automatyzacja, procesy kontroli, robotyka, wytwarzanie materiałów, technika lotnicza, trakcje elektryczne, elektronika, technika obronna, technika medyczna i biotechnologia).
EN
In article the generał characteristics of ferroic materials (crystals and ceramics) were showed. Ferroic crystals are those crystals which involve at least one phase transition which changes the directional symmetry of the crystal. The term ferroic materials is a generał term covering ferromagnetic materials (FM) ferroelectric materials (FE) and ferroelastic materials (FES). These three types of ferroics are called primary ferroics. Mechanicai or elastic analogue of ferromagnetism and ferroelectricity is called ferroelasticity. Materials exhibiting both ferroelectric and ferroelastic properties are called ferroelastoelectrics (FE+FES). The ferroics (FM, FE, FES) and ferroelastoelectrics (FE+FES) belong to family on smart materials. They be defined broadly that materials that can by altered or controlled by an extemal stimulus (magnetic, electric, mechanicai, thermal). Smart materials can by used in a variety of applications and in diverse industries such as automation, process control, robotics, materials processing, aerospace, automotive, electronics, defense technologies and medical technique.
15
Content available remote Dielectric relaxation modes in ferroelectric liquid crystal 2H6B
Wojciechowski M.
Scientific Bulletin. Physics / Lodz University of Technology
|
2006
|
Vol. 27
77-89
EN
A ferroelectric liquid crystal compound (2H6B) has been studied by means of low frequency dielectric spectroscopy. This compound shows only one chiral smectic phase, ferroelectric phase SmC. In this compound two dielectric relaxation modes (soft mode and Goldstone mode) related to collective molecular fluctuation were registered. In this work the dielectric characteristics and discussion of relaxation processes in ferroelectric phase are presented.
PL
Ferroelektryczny ciekły kryształ 2H6B był badany za pomocą spektroskopii dielektrycznej. W pracy przedstawiono dielkektryczne charakterystyki poszczególnych faz oraz interpretację zarejestrowanych procesów relaksacyjnych. W fazie ferroelektrycznej zarejestrowano nietypowe temperaturowe zależności częstości relaksacji oraz inkrementu dielektrycznego niskotemperaturowej części fazy ferroelektrycznej sugerujące ferrielektryczne własności w temperaturach poniżej 65°C.
16
Content available remote Technologia wytwarzania, właściwości i możliwości aplikacyjne elektroceramiki ferroelektrycznej. Część I. Synteza ceramicznych proszków ferroelektrycznych
Surowiak Z., Bochenek D., Machura D., Nogas-Ćwikiel E., Płońska M., Wodecka-Duś B.
Materiały Ceramiczne
|
2006
|
R. 58, nr 4
120-130
PL
W artykule przedstawiono procesy syntezy wybranych ferroelektrycznych proszków ceramicznych. Optymalizowano warunki syntezy następujących ferroelektryków: PZT, PLZT, (Ba(1-x)Pbx)TiO3, A(m-1)Bi2BmO(3m+3), A(2m-2Bi4B2mO(6m+6), SNN i SBN. Przy doborze ferroelektryków brano pod uwagę możliwości ich praktycznych zastosowań. Ferroelektryczne proszki ceramiczne syntezowano dwiema metodami: (1) wysokotemperaturową reakcją w fazie stałej i (2) niskotemperaturową metodą zolowo-żelową. W badaniach procesu syntezy korzystano między innymi z następujących metod: analiza termiczna (TA), rentgenowska dyfrakcja proszkowa (X-RD) i skaningowa mikroskopia elektronowa (SEM) w połączeniu z układem (EDS). W następnej Części II będą przedstawione niektóre właściwości otrzymanych ferroelektrycznych proszków ceramicznych.
EN
This paper presents the synthesis process of different ferroelectric ceramic powders. The conditions of synthesis the following ferroelectrics were optimized: PZT, PLZT, (Ba(1-x)Pbx)TiO3, A(m-1)Bi2BmO(3m+3), A(2m-2)Bi4B2mO(6m+6), SNN and SBN. The possibility of practical applications of ferroelectrics was taken under attentions. The following methods to synthesis of ferroelectric ceramic powders were used: (1) high-temperature reaction in solid phase and (2) Iow- temperature sol-gel process. Thermal analysis (TA), X-ray powder diffraction analysis (X-RD), scanning electron microscopy (SEM+EDS) equipped with energy dispersive system (EDS) was used to study of the synthesis process. In the next Part II some properties of the received ferroelectric ceramic powders will by presented.
17
Content available remote Analiza pełnofalowa anteny skanującej na podłożu ferroelekrycznym
Jaszczyszyn E.
Kwartalnik Elektroniki i Telekomunikacji
|
2004
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Vol. 50, z. 2
287-311
PL
W pracy przedstawiono koncepcję i opracowano nowy rodzaj skanującej anteny paskowej na podłożu ferroelektrycznym bez konieczności wykorzystania przesuwników fazy. Ponadto opracowano uogólnioną metodę analizy elektrodynamicznej rozpatrywanej struktury promieniującej wraz z metodą analizy numerycznej. Wyniki badań anteny skanującej wskazują na możliwość szerokiego jej zastosowania, a przedstawiona metoda analizy pełnofalowej do projektowania struktur promieniujących.
EN
Electronically scanned microwave antennas is accomplished by electronically altering the phase across the antenna radiating aperture (by means of discrete phase shifting elements or by changing frequency). This conventional inertialess scanning techniques in the microwave region are not cheap. A new scan antenna concept that realizable design using low-cost fabrication processes is presented. This concept is based on the first higher order mode on a microstrip line, which substrate is made using ceramic-polymer composite with modified ferroelectric powder Ba0,65Sr0,35TiO3 and appropriate polymer (grains of the powder have been sprayed into polymer with specific method). This ceramic-polymer composite was designed to change permittivity in response to an applied electric control field. The property of ferroelectric materials having a dielectric constant which can be modulated at high frequencies is very attractive. The feasibility of dielectric scanning (changing the direction of the beam by varying the relative permittivity of the electrically controlled ceramic-polymer composite) has been investigated. The radiation characteristics of such antenna have been accurate evaluated. Both longitudinal and transverse currents are treated. The method of solution used is an extension of the Fourier integral method which is used in conjunction with the method of moments (Galerkin solution). The propagation constant kx for higher order modes in open microstrip were calculated. In the present structure the complex propagation constant can be changed by changing the frequency or by changing the dielectric constant of the substrate (E2) as in the case of electrically controlled ferroelectric ceramic-polymer composite. In general, the direction of the radiated beam is given by Om = sin-1 (B), where kx (E2) = B(E2) = j * A(E2). For frequencies not far above the cut-off frequency, that means for B/k 0 < 1 (B in phase constant of the first higher order mode), the fields of the first higher order mode on the microstrip line are coupled to the line very loosely resulting in a considerable radiation.
18
Content available remote Badania właściwości materiałów ferroelektrycznych w zakresie mikrofal
Jaszczyszyn E., Szafran M., Modelski J., Bobryk E.
Kwartalnik Elektroniki i Telekomunikacji
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2003
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Vol. 49, z. 2
247-256
PL
W pracy przedstawiono impulsową metodę do pomiaru parametrów materiałów ceramiczno-polimerowych, przydatnych do zastosowań w zakresie mikrofal. Przeprowadzono także badania kompozytowych warstw ceramiczno-polimerowych zawierających modyfikowany ceramiczny proszek ferroelektryczny typu Ba0.65Sr0.35TiO3 oraz odpowiedni polimer, w którym w sposób dyskretny rozproszone zostały ziarna tego proszku. Otrzymane współczynniki przestrajania skutecznej przenikalności elektrycznej pozwalają stwierdzić, że warstwy takie nadają się do opracowania nowych typów anten oraz podzespołów mikrofalowych.
EN
Pulse method for microwave measurement of the ceramic-polymer materials parameters has been developed. Ceramic-polymer composite substrates with modified ferroelectric powder Ba0.65Sr0.35TiO3 and appropriate polymer (grains of the powder have been sprayed into polymer with specific method) have been also investigated. The powder Ba0.65 Sr0.35TiO3 has been synthesized at the temperature range 1150-1350C/3h and admixture (from 0,5% to 3%) of oxides of nickel or manganese or iron have been added. The ferroelectric powder after being granulated (into grinder) according to desired size (1-5 um) has been utilized in order to obtain ceramic-polymer films. The substrates of the ceramic-polymer composite have been designed such that volume of the ferroelectric powder was from 75% to 97,5%. However, volume of the polymer was at the range from 2,5 to 25%. Thickness of the composite layer has been chosen from 100 to 500 um. The type of the polymer required for obtaining the composite with desired parameters has been also investigated. Main properties of the composite are mechanical resistance and flexibility. They permit to operate easy with obtained substrate and cover conductive plane with it. The polystyrene and polyvinyl butyral are the best among many investigated polymers. The proposed pulse method for microwave measurement of the ceramic-polymer materials parameters is based on measurement of the pulse delay to after pulse passed of the microstrip line fragment. The substrate of the microstrip line is realized with ferroelectric material. Utilizing this pulse method permits to accurately define the pulse delay without matched to microstrip, but it does not permit to assign losses. Because permittivities of the investigated materials are primarily unknown this way might be very useful. Microstrip line can be matched and the losses can be determined by changing pulse magnitudes. Obtained results (e.g. tuning ability coefficient of the effective permittivity) show that ceramic-polymer substrate can be utilized in designing new type of antennas and microwave devices.
19
Content available remote Synteza paskowych szyków antenowych na podłożu ferroelektrycznym
Jaszczyszyn E., Modelski J.
Kwartalnik Elektroniki i Telekomunikacji
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2002
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Vol. 48, z. 1
67-80
PL
W pracy przedstawiono nową metodę syntezy anten paskowych, przydatnych do zastosowań w systemach adaptacyjnych. Proponowana metoda polega na poszukiwaniu optymalnych kształtów charakterystyk promieniowania pojedynczych radiatorów w szyku antenowym (przez zmianę przenikalności elektrycznej podłoża ferroelektrycznego radiatora paskowego) bez konieczności stosowania przesuwników fazy i tłumików. W pracy przedstawione wyniki syntezy oraz porównanie proponowanej metody z ogólnie stosowanymi.
EN
ln modern radio system smart beamforming is often required. Communications antennas must offer a large number of operating modes (including pencil and shaped beams with fast switching between them) in order to ensure the best coverage of the service area. Therefore in designing smart antennas one of the main challenges is to provide a prescribed shaped antenna pattern that simultaneously suppresses interference signals (which locations are either known or unknown). As a rule this problem is solved with the use of phased-array antennas. This type of array consists of multiple stationary antenna elements which are fed coherently and use variable phase or time-delay control at each element to scan the beam to given angles in space. Variable amplitude control is sometimes also provided for pattern shaping. Performance of each radiating element bas significant influence on the parameters of antenna array, e.g. pattern, beamwidth, directivity gain, sidelobes, cross-polarization levels etc. Reducing the cost of phased array antennas has recently become the subject of considerable interest. The most prominent obstacle to this is the cost of current phase shifter elements (p-I-n diodes, MESFETs, ferrite). AIl of these are expensive, constituting a significant portion of the total receive-array cost. Additionally, p-I-n diodes and MESFETs introduce significant losses. These losses necessitate additional amplification of signal thus complicate the overall system design. New developments in MEMS and ferroelectric technologies promise low loss/high performance phase shifters. Both technologies provide low losses with beam capabilities, high isolation, good power handling ability, and low intermodulation distortion. Ferroelectrics are beneficial for applications operating at microwaves range, offering large phase shift per loss, low losses (0.2-0.3 dB, depending on frequency and matching), and large power handling capability. Bulk ferroelectric are beneficial for large phased array antennas because acceptable radiation characteristics may be achieved with fewer elements, lower cost, smaller size, and weight and lower power consumption. The design of a low-cost antenna array with 2D steering capability is very important for radiocommunication. As the satellite and mobile wireless communications technologies continue to utilize higher frequencies in the 20 to 60 GHz range, the design of a phased array antenna becomes prohibitively expensive. Also the realization od 2D scanning capability to track the satellite or to provide adequate urban communications systems becomes increasingly difficult to realize at a sufficiently low-cost suitable for the consumer market. The aim of this paper is to present a new method of array pattern synthesis by taking into consideration pattern of each radiator specially of the ferroelectric one. Radiating elements employing ferroelectric materials may give much better performance compared with ferrite ones, because of their high power handling capability, low drive power, full military temperature range of operation and low cost. The main feature of the ferroelectric antennas is the change of ferroelectric material permittivity with an applied dc control voltage. The permittivity change by varying the dc bias enables to create different radiation patterns. This permits to use such radiating element in several applications, e.g. smart antenna arrays. In this paper, new method of pattern synthesis of antenna arrays without phase shifters and attenuators has been presented. This concept is based on utilizing voltage-controlled ferroelectric array, where variable pattern of each antenna element is used to synthesize array pattrern.
20
Jonizacja atmosfery otaczającej ferroelektryk a zmiana jego polaryzacji
Kowalczyk R.
Zeszyty Naukowe. Fizyka / Politechnika Opolska
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1998
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z. 21
95-103
PL
Badano proces przepolaryzowania ferroelektryków w impulsowych wolnozmiennych polach elektrycznych i w polach przemiennych. Zmierzono napięcia progowe wywołujące mierzalną zmianę polaryzacji makroskopowej oraz napięcia, w których ferroelektryk ulegał całkowitemu spolaryzowaniu badź cyklicznemu przepolaryzowaniu. Badano także jonizację atmosfery otaczającej ferroelektryk w czasie zmian jego polaryzacji w polach elektrycznych. Stwierdzono, że jonizacja atmosfery rozpoczyna się w polach elektrycznych co najmniej o rząd wielkości wyższych od pól, w których ferroelektryk ulega spolaryzowaniu bądź przepolaryzowaniu. Potwierdzono także badania porównawcze dla dielektryków nie będących ferroelektrykami. Pomiary napięć progowych wywołujących jonizację atmosfery w samym układzie pomiarowym bez próbki oraz pomiary tych napięć dla próbek ferroelektrycznych i paraelektrycznych wskazują na to, że mechanizm jonizacji w obydwu wypadkach jest ten sam. Wyniki dalszych badań zmian polaryzacji wywołanych impulsowym i cyklicznym naprężeniem pozwolą lepiej zrozumieć mechanizm przepolaryzowania ferroelektryków.
EN
Phenomen of changing polarity of ferroelectrics under slow changed electric field and AC field, the both, were investigated. The value of threshold voltage for that phenomenon and the value of the voltage in which the sample of ferroelectric had changed its polarity were measured. Atmosphere surrounded the sample influenced both on the ratio of ionization as result and on the level of such an influencing were observed and then the phenomena were recorded. It had been measured that ionisation the atmosphere around the sample was about ten times higher than value of voltage in which the sample changed its polarity. The experiment for compare the features of sample of ferroelectric and the features of sample of ordinary dielectric observed the both in the same physical condition was done. It had been proved that running of phenomenon for ferroelectric sample and phenomenon for dielectric sample during the same process were with the without differences. The further results on polarity of samples of ferroelectric and its mechanical tension during electrical polarization would allow for better understanding the mechanism itself of changing polarity of ferroelectric samples.
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