PL
 |
EN
Ograniczanie wyników
Czasopisma help
  1. 5 Archives of Materials Science and Engineering
  2. 4 Archives of Metallurgy and Materials
  3. 4 Materials Science Poland
  4. 2 Ceramic Materials
  5. 2 Journal of Achievements in Materials and Manufacturing Engineering
Więcej...
Autorzy help
  1. 9 Bąk W.
  2. 6 Bochenek D.
  3. 6 Kajtoch C.
  4. 6 Surowiak Z.
  5. 4 Starzyk F.
Więcej...
Lata help
  1. 3 2020
  2. 3 2015
  3. 2 2013
  4. 3 2010
  5. 8 2009
Więcej...
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 29

Liczba wyników na stronie
first rewind previous Strona / 2 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  ferroelectrics
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 2 next fast forward last
1
Content available Technology and Dielectric Properties of the KNLN Doped with Nd3+ and Pr3+ Ions
Bochenek D., Osińska K., Mankiewicz M., Niemiec P., Dercz G.
Archives of Metallurgy and Materials
|
2020
|
Vol. 65, iss. 3
1183--1188
EN
The paper presents the technology and basic properties of three compositions of lead-free ceramics: (i) (K0.44Na0.52Li0.04)NbO3, (ii) (K0.44Na0.52Li0.04)NbO3)NbO3 +0.5%mol Nd2O3 and (iii) (K0.44Na0.52Li0.04)NbO3)NbO2+0.5%mol Pr2O3. Powders of the designed compositions based on KNLN were obtained with the classic ceramic technology, as a result of solid phase synthesis, from a mixture of simple oxides and carbonates. The synthesis of ceramic powders was carried out at Ts = 900°C for ts = 4 h, while compaction by free sintering at Tsint = 1100°C for tsint = 2 h. XRD studies have shown that doping with praseodymium and neodymium promotes the formation of the tetragonal phase in the base composition (K0.44Na0.52Li0.04)NbO3)NbO3 at lower temperatures. On the other hand, microstructural tests have shown that the admixture of neodymium and praseodymium improves the sinterability of ceramic samples during the technological process; however, the ceramic samples still exhibit high porosity.
2
Content available PZT-Type Ceramics Doped with Manganese, Antimony, Lanthanum and Tungsten - Technology and Physical Properties
Bochenek D., Niemiec P., Ćwikiel E., Goryczka T.
Archives of Metallurgy and Materials
|
2020
|
Vol. 65, iss. 2
827--837
EN
The work three ceramic compositions based on PbZr0.49 Ti0.51O3 doped with manganese (Mn), antimony (Sb), lanthanum (La) and tungsten (W) were obtained. The introduction of a set of admixtures was aimed at improving the sinterability of ceramic materials and optimizing its electrophysical parameters. Multi-component materials of the PZT-type with a general formula: Pb(PbZr0.49 Ti0.51)0.94 Mn0.021 Sb0.016 LayWz O3 (where y from 0.008 to 0.012 and z from 0.012 to 0.014) were prepared by the conventional mixed oxide method. After mixing and drying the powder mixtures were calcined in air at 850°C for 4 h, while densification of the powders was carried out by the free sintering method at 1150°C for 2 h. The final steps of technology were grinding, polishing, annealing and putting silver paste electrodes onto both surfaces of the samples for electrical testing. XRD, SEM, EDS, dielectric, ferroelectric, piezoelectric properties and DC electrical conductivity of the obtained ceramic compositions were carried out. X-ray tests of the crystal structure conducted at room temperature have shown that all obtained the PZT-type materials were a single phase (perovskite type) without the presence of a foreign phase. Symmetry of the crystal lattice was identified as space group P4mm. Temperature dielectric studies have shown high values of dielectric permittivity and low dielectric loss. The presented physical properties of ceramic samples based on PZT confirm their predisposition for application in modern microelectronic and micromechatronic applications.
3
Content available Alternative, Direct Synthesis Method of the Ceramic Solid Solutions Based on BaTiO3 Through a High Energy Ball Milling
Bąk W., Dulian P., Garbarz-Glos B., Czekaj D., Lisińska-Czekaj A.
Archives of Metallurgy and Materials
|
2020
|
Vol. 65, iss. 2
805--810
EN
Polycrystalline samples BaTiO3 and the solid solutions Ba0.9 Sr0.1 TiO3, 0.9 Sr0.1 Ti0.9 Sn0.1 O3, Ba0.9 Sr0.1 Ti0.8 Sn0.2 O3 were obtained by means of a mechanochemical treatment based on the high-energy ball milling technique and next a high temperature solid state reaction method. The influence of synthesis condition on microstructural, dielectric and ferroelectric properties of obtained solid solutions were investigated. The structure and morphology of the investigated samples were characterized by an X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterization of electrical properties of the ceramics within the temperature range from –130°C to 250°C were performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to10 MHz. The diffusion of the paraelectric – ferroelectric phase transition and dielectric relaxation for ceramic samples are described.
4
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.
5
Content available remote Rietveld refinement on XRD and TEM study of nanocrystalline PbZr0:5Ti 0:5O3 ceramics prepared with a soft chemistry route
Mandal T. K.
Materials Science Poland
|
2015
|
Vol. 33, No. 1
18--24
EN
PbZr0.5Ti0.5 O3 nanopowders (~27 nm) have been prepared by a controlled reconstructive thermal decomposition and crystallization from an amorphous polymeric precursor with polyvinyl alcohol (PVA) and sucrose at 400 to 700 °C in air. The Rietveld refinement of the XRD profiles which were recorded at room temperature for the PbZr0.5Ti0.5 O3 powder prepared by a thermal treatment at 700 °C for 2 h, confirmed the P4mm tetragonal crystal structure of the as prepared PbZr0.5Ti0.5 O3 nanopowders, with a = 0.4036 nm and c = 0.4147 nm. A hexagonal symmetry (R3c), with a = 0.5774 nm and c = 1.4212 nm, was also detected from Rietveld refinement analysis. Thus, tetragonal and hexagonal phases were found to coexist with the as prepared PbZr0.5Ti0.5 O3 nanopowders. The average particle size (D) of the PbZr0.5Ti0.5 O3 powders, estimated with the help of the specific surface area, measured by BET method, was 26.1 nm. Average D value, calculated by Δ2Θ1/2 in the XRD peaks with the Debye-Scherrer relation was ~24 nm. TEM study made it possible to measure the particle size of PbZr0.5Ti0.5 O3 powders with an average diameter of 27 nm.
6
Content available remote Optical properties of D-serine doped TGS crystals for pyroelectric sensors
Kurlyak V. Y., Stadnyk V. Y., Andriyevsky B. V, Romanyuk M. O., Kohut Z. O., Gaba V. M.
Materials Science Poland
|
2015
|
Vol. 33, No. 4
692--698
EN
Refractive and birefringence indices in the range of transparency of 300 to 700 nm for triglycine sulphate crystals doped with D-serine molecules have been measured in the temperature range of 290 K to 340 K. The obtained optical properties are discussed together with characteristic electrical features of these materials used as pyroelectric sensors for measurement of temperature. The experimental results obtained in this study will be necessary as the reference data for comparison with the calculated refractive indices of TGS + D-serine on the basis of density functional theory. Determination of the proper position of D-serine, will reveal the features of TGS + D-serine crystal structure necessary to achieve stable unipolarity.
7
Content available remote Phase, microstructure and dielectric properties of 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 ceramics prepared by sol-gel technique
Uddin S., Iqbal Y., Ullah A.
Materials Science Poland
|
2013
|
Vol. 31, No. 3
410--414
EN
0.94Bi0.5Na0.5TiO3-0.06BaTiO3 ceramics were fabricated by sol-gel technique. The XRD results revealed the formation of a single phase perovskite structured Bi0.5Na0.5TiO3-BaTiO3 at 600 °C. The SEM images showed dense microstructure and the optimum density of the ceramics sintered at 1100 °C was 5.2 g/cm3. The saturation polarization (P s ) was found to be increased with increasing temperature while the remnant polarization (P r ) was found to be increased gradually and then decreased abruptly near 85 °C, which could be attributed to the phase transformation. The coercive electric field (E c ) was found to be decreased gradually with increasing temperature. The maximum value of dielectric constant (ɛ r ) at room temperature was 800 and dielectric loss at 1 MHz was 0.07.
8
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.
9
Content available remote Effect of restricted geometry on structural phase transitions in KH2PO4 and NH4H2PO4 crystals
Tarnavich V., Korotkov L., Karaeva O., Naberezhnov A., Rysiakiewicz-Pasek E.
Optica Applicata
|
2010
|
Vol. 40, nr 2
305--309
EN
The dielectric response of crystalline NH4H2PO4 and KH2PO4–SiO2 and NH4H2PO4–SiO2 composites prepared by embedding salts into porous glasses with the average pore diameter of 320 nm has been studied at the temperature range of 85–300 K. An increase of the structure phase transition temperatures in embedded salts has been observed, which is supposedly due to tensile deformations of embedded crystalline particles. The antiferroelectric phase transition in confined ADP particles becomes diffuse in the temperature region around 10 K.
10
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.
11
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.
12
Content available remote Ferroelektryki w szkłach porowatych
Rysiakiewicz-Pasek E., Poprawski R.
Szkło i Ceramika
|
2009
|
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.
13
Content available remote Room-temperature ferromagnetism in Fe-doped Na0.5Bi0.5TiO3 crystals
Wang Y., Xu G., Yang L., Ren Z., Wei X., Weng W., Du P., Shen G., Shen G., Han G.
Materials Science Poland
|
2009
|
Vol. 27, No. 2
471--476
EN
Fe-doped Na0.5Bi0.5TiO3 crystals were synthesized and studied by X-ray diffraction, X-ray spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and magnetic property measurement system. Room-temperature ferromagnetism was observed in Fe-doped Na0.5Bi0.5TiO3 crystals. It was found that the magnetism of Na0.5Bi0.5TiO3crystals can be controlled by the Fe dopant concentration. The magnetism of the Fe-doped Na0.5Bi0.5TiO3 crystals develops from diamagnetism to ferromagnetism and paramagnetism on increasing the Fe doping concentration from 0 to 10 mol %. The results presented in this study may provide new insights to the problem of synthesizing more single-phase multiferroic materials which will hopefully lead to rich and fascinating fundamental physics.
14
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.
15
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.
16
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.
17
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.
18
Content available remote Dielectric spectroscopy study of Ba0.98Na0.02Ti0.98Nb0.02O3 ceramic
Bąk W., Gabryś M., Kajtoch C., Stanuch K., Starzyk F.
Archives of Materials Science and Engineering
|
2009
|
Vol. 39, nr 2
107-110
EN
Purpose: The purpose of this work was to investigate dielectric properties of new ceramic solid solution Ba0.98Na0.02Ti0.98Nb0.02O3 (BNTN2) within the temperature range 153 K - 473 K. Design/methodology/approach: The dielectric spectroscopy method was applied to measure frequency and temperature dependence of complex dielectric permittivity, complex admittance, phase angle. The frequency dependence of ac conductivity at constant temperature was analysed as well as reciprocal permittivity and dielectric modulus as functions of temperature and frequency were compared. The Curie-Weiss rule and its generalized formula were applied in outcomes analysis. Findings: The ferroelectric - paraelectric (FE - PE) phase transition occurring in BNTN2 was found as having diffusive nature. In the paraelectric phase at about 400 K the diffusivity of transition step is correlated with the same kind of transition in BaTiO3 (BT) (transition of FE - PE type) and with structural transition occurring in NaNbO3 (NN). Within the temperature range below Tm = 308 K, dependences of dielectric properties of BNTN2 ceramic on temperature and frequency was found as having relaxor type of behaviour. Research limitations/implications: The confirmations of achieved findings will be possible by more precise BNTN2 structure determination by means X-ray diffraction. Also closer explanation of FE - PE phase transition can be performed by dielectric measurements within broader frequency range up to 1.8 GHz ( diffusive versus relaxor character of transition). Originality/value: The new solid solution of BNTN2 was prepared. The structure of this material was characterized as dielectrically active and having FE - PE phase transition which was described.
19
Content available remote Characteristics of phase transitions in Ba0.995Na0.005Ti0.995Nb0.005O3 ceramic
Bąk W.
Archives of Materials Science and Engineering
|
2009
|
Vol. 39, nr 2
75-79
EN
Purpose: The purpose of this work was to prepare ceramic material BaTiO3 (BT) as well as solid solution of Ba1-xNaxTi1-xNbxO3 (for x = 0.005) (BNTN05) type and correlate their structural (polycrystalline) properties with phase transitions within the temperature range from 153 K to 473 K. Design/methodology/approach: The dielectric spectroscopy method has been applied to measure dielectric and electric parameters within the frequency from 20 Hz to 1 MHz. Findings: The measured dependences of: complex dielectric permittivity and its phase angle (between measuring voltage and current response) points out on complex phase transition character for both investigated materials. Experimental outcomes for BT are consistent with those already published. Achieved results in the case of BNTN05 are published here for the first time. They were correlated with those of BT as unmodified one. Phase transitions parameters of both materials were described by means of generalised Curie-Weiss rule including step of phase transition diffusivity. Small amount (x = 0.005) of NaNbO3 (NN) admixture makes sharp, classical transition of first order kind occurring in the case of BT, to be a diffusive one and shifted by about 20 K towards lower temperatures. Research limitations/implications: Further investigations should be carried out in a broaden frequency range (up to 1.8 GHz) in order to establish the influence of network dynamics on ferroelectric-paraelectric phase transition as well as others low-temperature phase transitions. In order to complete structural data of new BNTN05 material additional X-ray and calorimetric measurements will be performed. Originality/value: The same method and components were used for preparation of BT and new BNTN05 material. Thermally induced phase transitions, mutually related in both materials were measured and described.
20
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.
first rewind previous Strona / 2 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.