In this study, we want to realize the influence of temperature on the ferroelectric liquid crystal flow and rubbing strength on the surface free energy of the polyimide thin film. The rubbing strength is determined by pile impress and the number of rubbing. The surface energy of the samples is measured. On the other hand the ferroelectric liquid crystal flow on the polyimide thin film was observed using a polarizing microscope. We found that the polyimide film treated by rubbing the surface properties will become non-uniformity. When the number of rubbing increased to a certain extent, polar energy is not changed, white disperse energy is continued to show fluctuations. In liquid crystal flow observation, we found that when the polyimide thin film temperature is low, the flow of ferroelectric liquid crystal is relatively slow, and its flow direction is in rubbing direction. When the polyimide thin film temperature is high, ferroelectric liquid crystal has two-dimensional flow. In addition to the direction of the original rubbing direction, but also increased the flow in the direction of the vertical rubbing.

The aim of this study is to produce Nb doped PZT thin films and then investigate the effects of Nb+5 ion on the structural, dielectric and ferroelectric properties. Niobium (Nb) doped lead zirconate titanate thin films (PNZT) were produced by solution deposition with nominal compositions, Pb(1-0.5x)(Zr0.53Ti0.47)1-xNbxO3 where x = 0.00 - 0.07. Single and multi-layered films were deposited onto (111)-Pt/Ti/SiO2/Si-(100) substrates by spin coating. PZT compositions near the morphotropic phase boundary (MPB) was chosen because excellent ferroelectric and dielectric properties were achieved in this area. The effects of sintering temperature, sintering time, variation of thickness in the films and change of niobium content were investigated with regard to phase development, microstructure, and ferroelectric and dielectric characteristics. The best results were obtained in double layered films (390 nm) which were sintered at 600 &deg / C for 1 h. Grain size of the films decreases with increasing Nb content except for 1 at % Nb doped films. The average grain size of 1 at % Nb doped thin films was calculated as 130 nm by using FESEM. Optimum doping level was found in 1 at % Nb doped films. For 1 at % Nb doped [Pb0.995(Zr0.53Ti0.47)0.99Nb0.01O3] films, remnant polarization (Pr) of 35.75 &amp / #956 / C/cm2 and coercive field (Ec) of 75.65 kV/cm have been obtained. The maximum dielectric constant was achieved in 1 at % Nb doped films which was 689. Tangent loss values were found between 2-4 % and these values were independent of Nb concentrations. Ferroelectric and dielectric properties were decreased at higher Nb doping levels because of the changes in the grain size, distortion of the crystal structure and pinning of the domains.

System integration and miniaturization demands are driving integrated thin film capacitor technologies with ultra-high capacitance densities for power supply integrity and efficient power management. The emerging need for voltage conversion and noise-free power supply in bioelectronics and portable consumer products require ultra high-density capacitance of above 100 μF/cm2 with BDV 16-32 V ,independent capacitor array terminals and non-polar dielectrics. The aim of this research,therefore, is to explore a new silicon- compatible thin film nanoelectrode capacitor technology that can meet all these demands. The nanoelectrode capacitor paradigm has two unique advances. The first advance is to achieve ultra-high surface area thin film electrodes by sintering metallic particles directly on a silicon substrate at CMOS- compatible temperatures. The second advance of this study is to conformally- deposit medium permittivity dielectrics over such particulate nanoelectrodes using Atomic Layer Deposition (ALD) process. Thin film copper particle nanoelectrode with open-porous structure was achieved by choosing a suitable phosphate-ester dispersant, solvent and a sacrificial polymer for partial sintering of copper particles to provide a continuous high surface area electrode. Capacitors with conformal ALD alumina as the dielectric and Polyethylene dioxythiophene (PEDT) as the top electrode showed 30X enhancement in capacitance density for a 20-30 micron copper particulate bottom electrode and 150X enhancement of capacitance density for a 75 micron electrode. These samples were tested for their mechanical and electrical properties by using characterization techniques such as SEM, EDS, I-V and C-V plots. A capacitance density of 30 μF/cm2 was demonstrated using this approach. The technology is extensible to much higher capacitance densities with better porosity control, reduction in particle size and higher permittivity dielectrics.

Abstract Ferroelectric/ferroelastic ceramics are used in a range of smart structure applications, such as actuators and sensors due to their electromechanical coupling properties. However, their inherent brittleness makes them susceptible to cracking and understanding their fracture is of prominent importance. A numerical study for a stationary, plane strain crack in a ferroelastic material is performed as part of this work. The stress and strain fields are analyzed using a constitutive law that accounts for the strain saturation, asymmetry in tension versus compression, Bauschinger effects, reverse switching, and remanent strain reorientation that can occur in these materials due to the non-proportional loading that arises near a crack tip. The far-field K-loading is applied using a numerical method developed for two-dimensional cracks allowing for the true infinite boundary conditions to be enforced. The J -integral is computed on various integration paths around the tip and the results are discussed in relation to energy release rate results for growing cracks and for stationary cracks in standard elastic–plastic materials. In addition to the fracture studies, we examine the far field electromechanical loading conditions that favor the formation, existence and evolution of stable needle domain array patterns, using a phase-field modeling approach. Such needle arrays are often seen in experimental imaging of ferroelectric single crystals, where periodic arrays of needle-shaped domains of a compatible polarization variant coexist with a homogeneous single domain parent variant. The infinite arrays of needles are modeled via a representative unit cell and the appropriate electrical and mechanical periodic boundary conditions. A theoretical investigation of the generalized loading conditions is carried out to determine the sets of averaged loading states that lead to stationary needle tip locations. The resulting boundary value problems are solved using a non-linear finite element method to determine the details of the needle shape as well as the field distributions around the needle tips. / text

Abstract Ferroelectric/ferroelastic ceramics are used in a range of smart structure applications, such as actuators and sensors due to their electromechanical coupling properties. However, their inherent brittleness makes them susceptible to cracking and understanding their fracture is of prominent importance. A numerical study for a stationary, plane strain crack in a ferroelastic material is performed as part of this work. The stress and strain fields are analyzed using a constitutive law that accounts for the strain saturation, asymmetry in tension versus compression, Bauschinger effects, reverse switching, and remanent strain reorientation that can occur in these materials due to the non-proportional loading that arises near a crack tip. The far-field K-loading is applied using a numerical method developed for two-dimensional cracks allowing for the true infinite boundary conditions to be enforced. The J -integral is computed on various integration paths around the tip and the results are discussed in relation to energy release rate results for growing cracks and for stationary cracks in standard elastic–plastic materials. In addition to the fracture studies, we examine the far field electromechanical loading conditions that favor the formation, existence and evolution of stable needle domain array patterns, using a phase-field modeling approach. Such needle arrays are often seen in experimental imaging of ferroelectric single crystals, where periodic arrays of needle-shaped domains of a compatible polarization variant coexist with a homogeneous single domain parent variant. The infinite arrays of needles are modeled via a representative unit cell and the appropriate electrical and mechanical periodic boundary conditions. A theoretical investigation of the generalized loading conditions is carried out to determine the sets of averaged loading states that lead to stationary needle tip locations. The resulting boundary value problems are solved using a non-linear finite element method to determine the details of the needle shape as well as the field distributions around the needle tips. / text

Nowadays the ferroelectrics containing of several feroically active sublattices are very attractive, because interactions between these sublattices can caused novel phenomena. Antiferroelectrics, ferrielectrics and multiferoics belong to these materials. In this work new crystalline materials MNP2X6 (M = Cu, Ag; N=In, Cr, Bi; X=S, Se) were investigated, which have ferrielectric and multiferoic properties. The dielectric and electric properties of above mentioned materials have been investigated by broadband dielectric spectroscopy methods, which allows to analyze the collective processes related to order – disorder and displacive phase transitions, ions migration and freezing of dipoles (glassy state) in wide temperature (25 K - 500 K) and frequency (10-5 HZ - 3 GHz) ranges. By substitution or doping it becomes possible to tailor the ferroelectric materials to different properties. In this work is determined that the substitution of 10% Cu ions by Ag ions shifts the phase transition temperature of CuInP2S6 crystal toward lower temperatures while the addition of In ions shifts the phase transitions temperature toward the higher ones. The phase transition temperature difference is about 50 K for mentioned crystals. If the ferroelectric crystal CuInP2S6 is mixed with the antiferroelectric CuCrP2S6 the dipole glass phase occupies the middle of the phase diagram. The distribution of relaxation times has been calculated from the broadband dielectric spectra of dipolar glasses. The... [to full text] / Šiai dienai ypač populiarūs ferroelektrikai susidedantys iš kelių feroiškai aktyvių subgardelių, kurių persitvarkymas fazinio virsmo temperatūroje atskleidžia naujų, dar neaprašytų reiškinių. Prie šių medžiagų priskiriami antiferoelektrikai, ferielektrikai ir multiferoikai. Šiame darbe buvo tiriama nauja medžiagų šeimos MNP2X6 (M = Cu, Ag; N=In, Cr, Bi; X=S, Se ), kurios pasižymi ferielektrinėmis bei multiferoinėmis savybėmis, ir kurių dielektrines ir elektrines savybes galima efektyviai keisti įvedant priemaišas. Minėtų medžiagų dielektrinės ir elektrinės savybės buvo tiriamos dielektrinės spektroskopijos metodais, kurie leidžia tirti kristalų kolektyvinius reiškinius susijusius su tvarkos – netvarkos bei poslinkio tipo faziniais virsmais, jonų migracija bei dipolių užšalimu (stiklėjimu) plačiame dažnių (10-5 Hz iki 3 GHz) bei temperatūrų (25 K iki 500 K) intervaluose. Įvedus 10% Ag jonų vietoj Cu jonų ferielektriniame kristale CuInP2S6 fazinio virsmo temperatūra pasislenka į žemesnias temperatūras, o padidinus indžio koncentraciją fazinio virsmo temperatūra pasislenka į aukštesnes temperatūras. Minėtų kristalų fazinių virsmų temperatūrų skirtumas 50 K. Sumaišius skirtingomis proporcijomis feroelektriką (CuInP2S6) su antiferoelektriku (CuCrP2S6) stebima dipolinio stiklo fazė. Iš dielektrinių matavimų stiklo fazėje buvo paskaičiuota relaksacijos trukmių pasiskirstymo funkcija, kurios aprašymas dvigubos potencialinės duobės modeliu leido susieti mikroskopinius kristalo... [toliau žr. visą tekstą]

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Thesis (Ph.D.) -- McMaster University, 2002. / Adviser: Anthony Petric. Includes bibliographical referernces. Also available via World Wide Web.