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1

Control of optical active borates nanocrystals agglomeration

Cieślik I., Węgłowski R., Żmija J., Kurzydłowski K., Płocińska M., Oćwieja M.

Journal of Achievements in Materials and Manufacturing Engineering

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2013

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Vol. 61, nr 2

163--168

EN

Purpose: The purposes of this study explore the possibility of total control the agglomeration of nanoborates powders. The great potential of PDLCs can be enhanced by using dye-doped or nanoparticles-doped materials, such as borates [1]. It is important to know how to prepare nanoparticles in order to obtain a high level of dispersion in the composites. Otherwise, even small an agglomeration does not give a possibility on the appropriate characteristic of properties and interpretation of the results. The deagglomeration methods applied until now give the decrease of agglomeration to a lesser extent than our method. Characteristic size and shape of particles made with sol-gel process is difficult to perform. Design/methodology/approach: Nanopowders samples of YAB and LCBO were prepared with sol-gel method. Deagglomeration process was carried out using acetic acid. The morphology and size of nanopowders were investigated by scanning electron microscopy (SEM). The crystallite sizes were determinated with IPS UA method. Findings: It was confirmed that the acetic acid influence on the decrease of agglomeration. It was also determined of conditions for preparation borates nanopowders samples (concentration acetic acind time and temperature of drying prepared samples). We have proved that a reagent used for deagglomeration process does not affect the structure of the investigated nanoborates used in an experimental. Research limitations/implications: The results can be used to the prepared of nanocompades of borates to observe a morphology and reliable assessment of nanocrystalline size. Originality/value: Our study shows how to prepare a sample of particles to observe morphology and measure the size of nanograins. In our study we found excellent solution, the medium, which not influence the inorganic nanomaterial structure. Result seems to be excellent and very perspective. We have showed as that measurement type influence the results of particles size.

2

Common Agricultural Policy towards the development of mountain areas

Czekaj M., Żmija J.

Geomatics, Landmanagement and Landscape

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2013

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no. 4

21--33

EN

Mountain areas due to their specific character should be managed in that way, which delivers people from rural areas appropriate income, what enable preserving and maintaining social tradition, unique features of environment and cultural landscapes. Mountain areas and every activity connected with them are part of national heritage. Maintain sustainable development of mountain areas requires continue of agricultural production and assuring appropriate economic conditions. Hence dwellers of mountain areas should have opportunity to earn in nonagricultural sources. Development of mountain areas connected only with agricultural production would lead to the impoverishment of the local population. Hence to counteract this process, it is necessary to assure direct payments for farmers, and at the same time expand nonagricultural function of this region. It is necessary to enrich rural areas in the mountains by creating a diversity of natural and cultural landscape. And although may it be a conflict between the objectives of conservation and agricultural activity, it seems that they could be overcome against the benefits which such cooperation can bring people in mountain areas.

3

Separation of inorganic nanopowders using the concentration gradient method

Cieślik I., Żmija J., Ohams M.

Polimery

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2012

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T. 57, nr 7-8

558-561

EN

In the present paper a modified method to separate inorganic nanopowders using the concentration gradient method has been presented. Extraction of individual fractions as a non-destructive method has been discussed. The technique in question allows obtaining a grain size that varies from several micrometers down to several nanometers using simple devices and within a short time.

PL

Artykuł przedstawia technikę rozdzielania nanoproszków nieorganicznych za pomocą zmodyfikowanej metody gradientu stężeń na przykładzie boranu glinowo-itrowego. Opisana metoda separacji jest metodą nieniszczącą. Pozwala w krótkim czasie oraz za pomocą prostych urządzeń laboratoryjnych uzyskać frakcje nanocząstek o rozmiarach od kilkunastu mikrometrów do kilku nanometrów.

4

Misja nauk rolniczych w rozwoju polskiego sektora rolno-spożywczego

Haman J., Hołownicki R., Michałek R., Żmija J.

Inżynieria Rolnicza

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2012

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R. 16, nr 4, t. 1

465-483

PL

Sektor rolno-spożywczy spełnia kluczową rolę w Polskiej gospodarce. Polska eksportuje prawie jedną czwartą produkcji rolniczej. Wkład tego sektora, stanowiący 13% (15 mld Euro) całkowitej wielkości eksportu, plasuje artykuły spożywcze i surowce rolnicze na drugim miejscu po przemyśle motoryzacyjnym. Rolnictwo jest nie tylko miejscem pracy, ale jest także sposobem życia dla prawie połowy ludności Polski, która jest bezpośrednio lub pośrednio związana z produkcją rolniczą. Polskie rolnictwo nie rozwijałoby się bez rozwoju nauk rolniczych. Praca przedstawia najważniejsze zagrożenia dla nauk rolniczych oraz sposoby ich przezwyciężenia, a także główne kierunki badawcze. Podstawowym problemem Polskiej nauki jest niewystarczające wsparcie finansowe oraz niedocenianie nauk rolniczych. Niewłaściwe kryteria parametryczne oceny pracowników i jednostek naukowych, które zajmują się naukami rolniczymi ograniczają rozwój badań stosowanych niezbędnych do dalszej modernizacji krajowego sektora rolno-spożywczego. Zaproponowano główne kierunki badawcze, które mogą zwiększyć konkurencyjność Polskiego rolnictwa. Nowe technologie powinny tworzyć nowe miejsca pracy i dodatkowe źródła przychodów dla ludności rolniczej. Mogą także poprawić smak i podnieść bezpieczeństwo żywności, czego oczekują konsumenci. Dlatego powinny zostać opracowane, niskoenergetyczne, wodo oszczędne i przyjazne dla środowiska technologie szczególnie w zakresie rolnictwa ekologicznego, upraw niszowych oraz surowców do wytwarzania fitofarmaceutyków i suplementów diety. Takie działania powinny skutkować wzrostem przychodu małych gospodarstw (3-6 ha). Istniejąca oferta rynkowa produktów spożywczych powinna zostać uzupełniona produktami wytwarzanymi w gospodarstwach. Taki rodzaj produkcji w małej skali wymaga linii technologicznych o niewielkiej wydajności, których wybór jest aktualnie bardzo mały. Potrzeba zrównoważonego wykorzystania istniejących zasobów wymaga rozwoju technologii opartych na rolnictwie precyzyjnym, co wiąże się z badaniami interdyscyplinarnymi integrującymi teledetekcję, mechatronikę oraz technologię komputerową z badaniami rolniczymi w procesie ich wdrażania i upowszechniania w praktyce rolniczej.

EN

The agri-food sector plays a key role in the Polish economy. Almost a quarter of the Poland's agricultural production is exported. The value of agricultural products amounting to € 15 billion, and the contribution of this sector reaching 13% of the total export volume locates food on the second position after the automotive industry. The agriculture is not only the workplace, but it is a way of life for almost half of the Poland's population, either directly or indirectly involved in the agricultural production. The Polish agriculture would not progress without the development of agricultural sciences. The paper presents the most important threats for agricultural sciences and the ways to overcome them, as well as the main research activities that need to be undertaken. A primary problem of the Polish science is insufficient funding and underestimation of life sciences. The inadequate parametric evaluation criteria of the researchers and the research units dealing with agricultural science disturb development of the applied research, which is necessary to modernize the national agri-food sector. The research activities that are described determine further development and can increase the competitiveness of the Polish agriculture. New technologies should create new workplaces and additional sources of income for the rural population. They may also bring back natural taste and safety of food demanded by consumers. Thus, low-energy, water-efficient and environmentally friendly technologies should be developed, especially for organic farming, niche market high-value crops, and bio-, phyto- and dietary supplements. It may result in the increase of income of small farms (3-6 ha). The existing range of food products should be complemented with the traditional food produced on farms using small processing lines. This kind of small scale production requires specialized low capacity equipment, the range of which is currently quite poor. A demand for sustainable use of resources with limited environmental risk stimulates development of precision farming technologies which needs to be supported by interdisciplinary research integrating remote sensing, mechatronics and IT technology, and assisting implementation of them in agricultural practice.

5

Synthesis and characteristics of optical properties of crystalline YAl3(BO3)4:Cr,Ce

Cieślik I., Żmija J., Majchrowski A., Pępczyńska M., Morawiak P., Włodarski M.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 48, nr 1

24--28

EN

Purpose: The purpose of this study is to explore the possibility of conrol the grain size of YAB nanopowder and to investigate the optimum amount of dopant cerium or chromium ions in the matrix of YAB for luminescent intensity. Design/methodology/approach: Nanocrystalline samples of YAB were prepared by sol-gel method and calcination at 1273 K. The structure and morphology of nanopowders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and aerodynamic aerosol aerodynamic methods. Fluorescent intensity was measured by Fourier transform infrared (FTIR) and intersection of three-dimensional matrix (EM-EX) methods. Findings: It was confirmed that the mean size of the obtained particles depended on the chain length of the precursor polimer used for reaction. The luminescence of YAB doped with cerium and chromium ions was measured. Research limitations/implications: The results can be used in order to further develop sol-gel technology to obtain pure and doped YAB nanopowder. Originality/value: Single phase crystalline YAB synthesis was developed. The measurements XRD confirmed that doping of YAB with some of RE or TM ions favours the formation of additional phase YBO3, having the orgonic structure.

6

New organic electrochromic materials and theirs applieations

Żmija J., Małachowski M. J.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 48, nr 1

14--23

EN

Purpose: The aim of this work is to perform the review of the recent most important results of experimental and theoretical investigations connected with the electrochromic materials and their selected applications. Design/methodology/approach: The recent achievements in the field of designing and preparation methods of organic electrochromic materials and devices operating as optical data storage are presented. Findings: We pointed out the physical phenomena that are important in the electrochromic effect occurring in organic materials and which can be used in numerous devices. Such phenomena as the change, evocation, or bleaching of color resulted either by an electron-transfer (redox) process or by a sufficient electrochemical potential have been evaluated as occurring in prosperous devices. Examples of the application of the organic electrochromic materials in electrochromic devices are shown. Research limitations/implications: The main disadvantage of organic devices are reported to be connected with their short lives and weak resistivity to the moist but the improvements are advancing. Originality/value: Our review concerns the most recent findings in this area. We also show some recent examples of electrochromic devices.

7

Organic field-effect transistors

Małachowski M. J., Żmija J.

Opto-Electronics Review

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2010

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Vol. 18, No. 2

121-136

EN

The paper reviews the recent year publications concerning organic field-effect transistors (OFETs). A lot of works have been performed to help understanding the structural and electrical properties of materials used to construct OFETs. It has been established that in partially ordered systems, the charge transport mechanism is thermally activated and field-assisted hopping transport and the hopping transport between disorder-induced localized states dominate over intrinsic polaronic hopping transport seen in organic single crystals. Many research attempts have been carried out on the design of air-stable organic semiconductors with a solution process which is capable of producing OFETs with excellent properties and good stability when subjected to multiple testing cycles and under continuous electrical bias. Recent experiments have demonstrated ambipolar channel conduction and light emission in conjugated polymer FETs. These achievements are the basis for construction of OLED based displays driven by active matrix consisting of OFETs.

8

New organic photochromic materials and selected applications

Żmija J., Małachowski M. J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 41, nr 1-2

48-56

EN

Purpose: The aim of this work is to perform the review of the recent most important results of experimental and theoretical investigations connected with the photochromic materials and their selected applications. Design/methodology/approach: The recent achievements in the field of designing and preparation methods of organic photochromic materials and devices operating as tree-dimensional optical data storage. Findings: We pointed out the important role that play the photochromic effect in organic materials and which can be used as the above mentioned devices. Research limitations/implications: The main disadvantage of organic materials are reported to be to short their lives and weak resistivity to the moist but the improvements are advancing. Originality/value: Our review concerns the most recent findings in this area. We also show some recent examples of photochromic organic material application in 3D memory devices.

9

Estimation of surface supersaturation in Monte Carlo simulations of single crystal growth

Rak M., Brozi A., Żmija J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 41, nr 1-2

91-95

EN

Purpose: The aim of this study is to propose a new calculation method using Monte Carlo simulations making it possible to estimate surface supersaturation and its transient behavior. Design/methodology/approach: Monte Carlo simulation method is used for investigations of crystal growth from microscopic point of view. It is assumed that the surface supersaturation may be represented by the number of growth units adsorbed on the crystal surface at any given moment. Findings: The presented method allows us to analyze the surface configuration of a growing crystal face and the mechanism of single crystal growth in various assumed growth conditions (supersaturation, temperature). Research limitations/implications: The results of the performed simulations show the influence of changes in bulk supersaturation on the behavior of surface supersaturation, which is very difficult to experimentally measure. In this way, some analytical results calculated previously and concerning transient behavior of surface supersaturation can also be verified. Originality/value: For the first time, Surface Roughening Coefficient (SRC) is defined and the method of its calculation is shown. The SRC coefficient allows us to estimate surface supersaturation determining growth mechanism and, in consequence, determining the quality of grown crystals. The results are useful for control of growth process to obtain good quality single crystals.

10

Organic light emitting diodes operation and application in displays

Żmija J., Małachowski M.

Archives of Materials Science and Engineering

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2009

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Vol. 40, nr 1

5-12

EN

Purpose: The aim of this work is to perform the review of the recent most important results of experimental and theoretical investigations connected with the organic light emitting devices (OLEDs). Design/methodology/approach: The recent achievements in the field of designing, fabricating and clarification of the OLEDs operation have been presented. The possibilities of numerous, present and future applications of these devices have been pointed out. Findings: We show that fundamental differences among organic and inorganic devices result from differences between inorganic and molecular semiconductor materials. No charges are present in OLED devices without charge injection. Emission is due to radiative transitions from the neutral excited states to the ground states. We pointed out the important role that the OLEDs play in display design (even the flexible ones). Research limitations/implications: The main disadvantage of OLEDs is reported to be short their lives (particularly the blue OLED) and weak resistivity to moist but improvements are advancing. Originality/value: Our review concerns the most recent experimental and theoretical publications in the OLED investigation. We also show some recent examples of OLEDs application.

11

Dielectric properties of polycrystalline (Ba0.40Sr0.60)O3

Kajtoch C., Bąk W., Gabryś M., Mroczka K., Starzyk F., Żmija J.

Archives of Materials Science and Engineering

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2009

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Vol. 40, nr 1

33-36

EN

Purpose: Purpose of this paper is to qualify of the degree and the causes of broadening of the phase transition in the polycrystalline solid solution (Ba0.40Sr0.60)TiO3 (BS60T). Design/methodology/approach: Polycrystalline samples of (Ba0.40Sr0.60)TiO3 (BS60T) were prepared by calcinations method at temperature 1570K. 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 Agilent Precision LRC meter HP4824A equipped with WinDETA 5.62 software Novocontrol. Measurements were taken under cooling with 2K/min speed. Measuring electric field frequency was from the range 20 Hz - 1 MHz. Findings: The dielectrometry was applied to measure complex dielectric permittivity and other dielectric functions of ferroelectric (BS60T). It was affirmed, that 60% substitution of Sr ions changed the type of phase transition. Weak dependence of temperature Tm=208 K (temperature of maximum electric permittivity &epsilon') on frequency of the external electric field testifies about diffused character of the phase transition (DPT). The polar character of this material was also observed in the paraelectric phase (to 360 K). This observation is connected with the occurrence of polar clusters in this phase. Research limitations/implications: Results can be used in order to describe the phase transition modifications in the solid solutions with ferroactive substitutions in sublattice B of the perovskite. Originality/value: Value of this work relies on the experimental examination of the electric properties of BS60T solid solution. The low value of phase angle in the paraelectric phase is connected with the occurrence of the polar regions (clusters).

12

Photochromic effects in sillenite single crystals

Żmija J., Małachowski M.

Archives of Materials Science and Engineering

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2008

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Vol. 33, nr 2

101-106

EN

Purpose: The aim of this work was to fabricate the doped with transition or rare earth metals the single crystals such as Bi12GeO20 (BGO) and Bi12SiO20 (BSO), showing the photochromic effect and to study this effect. Findings: To the study results we can count the development of the mentioned single crystal technology and the measurement set as well as the interpretation of the obtained absorption spectra. Research limitations/implications: Among others we have found that the photochromic effect in these materials is connected with the change in doped atom charge state by one electron ie. Mn+4 → Mn+5 and Cr+3 → Cr+4. We also propose the schematic presentation of the energetic levels obtained on the basis of the above remarks. Originality/value: The authors show, for the first time, the photochromic effect in doped with transition or rare earth metals the BGO and BSO single crystals and developed the model explaining this effect. The similar studies were performed on the BTMO (T=Ti, M=Pb) mixed crystals. The applications are connected with the areas of scientific studies of some single crystals as well as using them in particular devices.

13

Evolution of electric polarization in paraelectric phase of BaTiO3

Bąk W., Kajtoch C., Starzyk F., Żmija J.

Archives of Materials Science and Engineering

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2008

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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.

14

Postępy w badaniach fotoprzewodnictwa monokryształów sillenitów mieszanych

Żmija J., Majchrowski A., Szymczak H., Borowiec M. T.

Chemistry-Didactics-Ecology-Metrology

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2006

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R.11, NR 1-2

61--68

PL

Opracowano technologię krystalizacji z roztworów wysokotemperaturowych topiących się niekongruentnie sillenitów i otrzymano mieszane monokryształy Bi12Ti1-xPbxO20 (BTPbO) (x = 0,08; 0,16; 0,23; 0,36; 0,46; i 0,56), monokryształy Bi25FeO40 (BFeO) oraz mieszane monokryształy Bi12Ti1-xFexO20 (BTFeO, x = 0,3). Określono górną granicę zawartości jonów ołowiu w mieszanych monokryształach BTPbO. Maksymalne wartości fotoprzewodnictwa uzyskano dla monokryształów o nominalnej wartości x = 0,2. Przeprowadzono badania fotoprzewodnictwa w szerokim przedziale spektralnym w funkcji temperatury, częstotliwości (światło modulowane) i składu (wartości x). Zaobserwowano dwa typy zależności fotoprzewodnictwa od temperatury. Do pierwszej grupy należą monokryształy sillenitów z żelazem, dla których fotoprzewodnictwo zanika ze zmniejszeniem temperatury. Do grupy drugiej należą sillenity mieszane BTPbO, dla których zależność temperaturowa jest wieloekstremowa. Wszystkie widma fotoprzewodnictwa zbadanych monokryształów sillenitów prostych i mieszanych składają się z trzech części: niskoenergetycznej odpowiadającej fotoprzewodnictwu „domieszkowemu”; o energii pośredniej związanej z fotojonizacją polaronu; wysokoenergetycznej odpowiadającej przejściu pasmo - pasmo.

EN

Crystallization from high temperature solutions of incongruently melting sillenites has been developed. Single crystals of Bi12Ti1-xPbxO20 (BTPbO) (x = 0.08; 0.16; 0.23; 0.36; 0.46; and 0.56), Bi25FeO40 (BFeO) and Bi12Ti1-xFexO20 (BTFeO, x = 0.3) have been obtained. The upper level of Pb concentration in mixed BTPbO single crystals has been found. Maximal photconductivity has been obtained for BTPbO samples grown from melts containig 20 at.% of lead. Sillenite photoconductivity has been investigated in a broad spectral range in dependence of temperature, frequency (modulated light) and concentration of components. Two modes of photoconductivity-temperature dependences have been found. In sillenites containing iron the photoconductivity vanishes with decreasing temperature. In case of mixed BTPbO sillenites the dependence has multi-peak shape. All spectra of investigated sillenites consist of three parts: low-energy part corresponding to dopants photoconductivity; medium-energy part connected with ionization of polarons; high-energy part connected with bandband transitions.

15

Materiały organiczne w elektronice

Żmija J., Małachowski M. J., Zieliński J., Wacławek M., Ścieżka K.

Chemistry-Didactics-Ecology-Metrology

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2006

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R.11, NR 1-2

69--80

PL

Przedstawiono przegląd wykorzystania materiałów organicznych w optoelektronice. W ostatnich latach widoczne są znaczne postępy w tym względzie zarówno naukowe, jak i aplikacyjne. Stwarza to realne podstawy, aby sądzić, że powstaje nowa licząca się gałąź nauki powiązana z interesującymi zastosowaniami, które w zakresie ciekłych kryształów (CK) są realizowane od dawna. Najnowsze publikacje pokazują niewątpliwe perspektywy inżynierii materiałowej w badaniach oraz zastosowaniu stałych półprzewodników organicznych. Omówiono ostatnie osiągnięcia w konstrukcji displejów CK, fotoogniw, ogniw słonecznych, emiterów LED, laserów oraz elementów mikroelektronicznych, zwłaszcza cienkowarstwowych tranzystorów.

EN

Review of papers connected with wide aspects of organic material engineering and its application in optoelectronics is presented. It creates an actual basis for new important branch of science and technology, which in LC case has been realized for decades already. Last achievements in fabrication of LC displays, photoelements, solar cells, OLEDs, lasers and microelectronic devices especially thin film transistors are presented. It is evident that a significant progress in science, technology and application of organic materials has been achieved.

16

Li+ ionic conductivity calculations of solid electrolytes on polymeric basis

Rewiński A, Łukaszewicz T., Żmija J.

Journal of Technical Physics

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2005

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Vol. 46, no 2

97-105

EN

This paper presents a theoretical approach to Li+ ions diffusion in polymeric solid electrolytes. The following parameters were calculated and then compared with the experimental results: the mobility of lithium ions, diffusion coefficient and recombination probability. Ionic conductivity of the electrolyte was also calculated.

17

Poszukiwanie fotonadprzewodnictwa w monokryształach sillenitów

Żmija J., Majchrowski A., Szymczak H., Borowiec M. T.

Chemistry-Didactics-Ecology-Metrology

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2004

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R. 9, NR 1-2

9--20

PL

Opracowano technologię monokrystalizacji mieszanych sillenitów Bi12Ti1-xPbxO20 (M = V, Ga, Pb, Cu) z rozbvorow wysokotemperaturowych metodą TSSG (Top Seeded Solution Growth - w wyniku wzrostu na zorientowanych zarodziach). Zbadano zależności temperaturowe fotoprzewodnictwa tych materiałów. W stosunku do najlepszych do tej pory znanvch fotoprzewodnikow sillenitowych właściwości fotoprzewodzące poprawiono o 4÷5 rzędów wielkość, w warunkach stałego oświetlenia. Udokumentowano zmiany oporności właściwej indukowane światłem w przedziale 15÷17 rzędów wielkości. Stwierdzono, że największe fotoprzewodmctwo występuje Bi12Ti1-xPbxO20 (x = 0,2). Jest ono związane z generacją ziaren metalicznych w Bi12Ti1-xPbxO20.

EN

Technology of mixed sillenites Bi12Ti,.xMxO20 (M = V, Ga, Pb, Cu) single crystal growth from high temperature solutions (Top Seeded Solution Growth - TSSG) has been developed. Temperature dependences of photoconductivity for these materials have been investigated. In comparison to known photoconducting sillenites, their photoconductivity was increased by 4-5 orders of maenitude. The changes of resistivity induced by illumination has been found to occur in the range of 15-17 orders of magnitude. The highest photoconductivity has been found in Bi12Ti1-xPbxO20 (x=0.2). It was connected with formation of metallic grains in Bi12Ti1-xPbxO20.

18

Molecular parameters of some antiferroelectric liquid crystals

Raszewski Z., Rutkowska J., Perkowski P., Zieliński J., Kędzierski J., Piecek W., Kłosowicz S., Żmija J.

Biuletyn Wojskowej Akademii Technicznej

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2002

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Vol. 51, nr 1

21-33

PL

W pracy zbadano dwa związki ciekłokrystaliczne MHPB(H)PBC oraz MHPB(F)PBC wykazujące właściwości antyferroelektryczne, zsyntezowane w WAT. Wyznaczono szereg wielkości charakteryzujących fazę jak: kąt tiltu θ, polaryzację spontaniczną Ps w fazie anty- i ferroelektrycznej. Na podstawie pomiarów optycznych oraz densytometrycznych, korzystając z dwóch różnych procedur ekstrapolacyjnych, obliczono polaryzowalności (αL i αT) molekuł tworzących fazę ciekłokrystaliczną. Wartość momentów dipolowych wyznaczono z pomiarów dielektrycznych w fazie izotropowej (korzystając z równań Maiera - Meiera) oraz z modelowania komputerowego za pomocą programu Hyper Chem 5.0.

EN

Two investigated antiferroelectric liquid crystals, MHPB(H)PBC and MHPB(F)PBC, were synthesized [1] and some their physical properties were described earlier [2]. Apart from the above, MHPB(H)PBC and MHPB(F)PBC have been studied by means of dielectric, densitometric, refractometric and X-ray measurements. Spontaneous polarisation and tilt angle θ in ferro- (SmC*) and antiferroelectric (SmC*A) phases of MHPB(H)PBC and MHPB(F)PBC have also been invastigated. Transverse αT and longitudinal αL molecular polarizabilities have been calculated from the ordinarynO and extraordinary nE refractive indices and densityρ of MHPB(H)PBC and MHPB(F)PBC, using Neugebaure, Vuks and Lorentz wquations with both Haller and Subramhanyama extrapolation procedures. Effective values of the molecular dipole moment have been calculated from electric permittivity in the I phases of these compounds, using Maier and Meier equation.

19

Determination of quadrupolar ordering in ferroelectric liquid crystals SmC*. Part 2, Experimental results

Raszewski Z., Kędzierski J., Perkowski P., Rutkowska J., Piecek W., Zieliński J., Żmija J., Dąbrowski R., Ranga Reddy R.

Biuletyn Wojskowej Akademii Technicznej

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1999

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Vol. 48, nr 4

47-55

EN

We synthesized the compound: 2-methylbutyl-4-n-nonanoyloxybiphenyl-4'-carboxylate (MBOBC) [formula] with shows the inversiors in the sign of the spontaneous polarization reported for the first time by Eidenschink et al.[1] and Goodby et al.[2, 3]. These ferroelectric liquid crystals have been studied using dielectric, densytometric, refractometric and X-ray methods. On the basis of these measurements and computer modelling for this molecule, the molecular dipole moment μ, mean molecular polarizability ά as well as angles gamma and γ and φ0 between vector μ, and long n and short l molecular axes of intertia have been calculated. The investigated compound exhibits smectic C* phase with negative spontaneous polarization Ps at higher temperatures and changes the sign at T(N-P) to give positive P(S) at lower ones. Apart from the sign and the magnitude of spontaneous polarization P(S), the tilt angle Θ, helical pitch γ, density, refractive indices and dielectric permittivities have been measured for the same FLC.

PL

W pracy przedstawiono szczegółowe wyniki pomiarów wartości i znaku polaryzacji spontanicznej, kąta tiltu, skoku helikoidy, gęstości, współczynników załamania światła i przenikalności dielektrycznej w funkcji temperatury dla ferroelektrycznego ciekłego kryształu nonanjon-4-(2-metylobutylo)-4'-hydroksybifenylu (MBOBC). Na podstawie wyników przeprowadzonych pomiarów posiłkując się obliczeniami półempirycznych metod kwantowych wyznaczono parametry molekularne molekuły badanej substancji: μ, γ, φ0, ά. Typując do badań substancję MBOBC kierowano się tym, że wykazuje ona inwersję znaku Ps. Zmiana wraz z temperaturą T wielkości i znaku Ps stwarza potencjalne możliwości potwierdzenia spójności proponowanej przez autorów w kolejnej pracy zamieszczonej w tym samym numerze Biuletynu WAT teorii opisu Ps, jak i prześledzenia zmagań dwóch głównych żywiołów : "dipolowego" i "kwadrupolowego" w procesie ferroelektrycznego porządkowania momentów dipolowych SmC*.

20

Determination of quadrupolar ordering in ferroelectric liquid crystal SmC*. Part 1, Theoretical investigations and results

Raszewski Z., Kędzierski J., Perkowski P., Rutkowska J., Piecek W., Zieliński J., Żmija J., Dąbrowski R., Ranga Reddy R. N. V.

Biuletyn Wojskowej Akademii Technicznej

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1999

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Vol. 48, nr 4

35-45

EN

To explain the spontaneous polarization Ps behavior of the investigated compound 2-methylbutyl 4-n-nonanoyloxybiphenyl-4'-carboxylate (MBOBC) the rotational potential U(psi) given by Źeks [1] and modified by us [2, 3] has been used. Knowing the rotational potential U(psi),some molecular and state parameters and additionally under assumption, that we know the angles omega, gamma between chiral d and quadrupolar b coupling axes with l molecular one [4], the spontaneous polarization Ps has been calculated as the vector sum of the components of molecular dipole moment perpendicular to the tilt direction. After comparing the Ps taken from experiment and obtained from theoretical approximation, the contribution of the dipolar a1 and quadrupolar a2 terms in the rotational potential have been estimated. In terms of the rotational potential, the Ps inversion can be easily explained as the displacement of the angular position psiM of the minimum of U(psi) versus temperature.

PL

Znając potencjał rotacyjny U(Psi), parametry molekularne Mi, Gamma, Fi0, Alfa molekuł, z których zbudowany jest FLC, parametry stanu Lambda i Theta smektyka C* oraz dodatkowo kąty jakie tworzą oś "chiralna"d i oś "kwadrupolowa" b z krótką osią molekuły l, możemy wyznaczyć polaryzację spontaniczną Ps jako wektorową sumę składowych prostopadłych (do płaszczyzny pochylenia) momentów dipolowych. Porównując wyprowadzoną na gruncie powyższego modelu FLC teoretyczną formułę na polaryzację spontaniczną Ps z charakterystykami eksperymentalnymi badanej substancji, wyznaczono parametry a1, a2 i a3 potencjału rotacyjnego Zeksa, a tym samym określono wkłady poszczególnych oddziaływań (a1-dipolowego, a2-kwadrupolowego oraz a3-fleksoelektrycznego) w procesie porządkowania dipoli elektrycznych Mi fazy SmC*. W świetle rozważań zachowania Ps na gruncie potencjału rotacyjnego molekuły chiralnej w ośrodku FLC, inwersja znaku polaryzacji spontanicznej jest konsekwencją przemieszczania się wraz z temperaturą pozycji kąta , dla którego osiąga minimum.