<p>With the development of wireless communication technology, second-, third-, fourth-generation transmission systems based on electromagnetic (EM) waves are widely used. At the same time, public concerns have been raised about whether the use of such systems will have an impact on health and safety standards. The heating effect is the most prominent and scientifically verifiable biological effect. So, the influence of EM waves on human body is addressed by studying the heating characteristics on head models.</p> <p>The objective of this thesis is to study the effects of radio frequency (RF) waves radiation from mobile phones on the human head under different transmission generations. The six-layer head model is used to evaluate the specific absorption rate (SAR) distribution and thermal effect. This model allows to study the effects of SAR and temperature rise without the need for high computational resources. In order to find the effect of temperature rise and exposure time, the finite difference time domain (FDTD) method was used to solve the biothermal equation with appropriate boundary conditions.</p> <p>Also, different age-dependent head models are used to study the differences of SAR for children at different ages.</p> <p>In general, the results show that with the increase in frequency, the influence of the EM wave is more pronounced, as demonstrated by the SAR and temperature rise distribution. In addition, SAR distribution of younger ages show a significant increase, which indicates that children exposed to EM waves are subject to more harmed. </p>

A literature review on the topic of ferroic and multiferroic solid solutions of BaTiO3, SrTiO3 and EuTiO3 forms the first part of this master thesis. The second part describes the experimental preparation and evaluation of the properties of samples of europium strontium titanates - EuxSr1-xTiO3. First, the high temperature solid state synthesis was carried out and relative density and open porosity of the sintered samples were evaluated. The sintered samples showed open porosity higher than 10%. The reasons for this behavior were evaluated and described from the point of view of experimental conditions and thermodynamical calculations. Finally, electric and dielectric properties of selected samples were measured. These results show that these samples are insulators and their residual conductivity is caused probably by oxygen vacancies, arising from the synthesis in a strongly reducing atmosphere of pure hydrogen.

Polymer-derived ceramics (PDCs) are a unique class of multifunctional materials synthesized by thermal decomposition of polymeric precursors. Due to their unique and excellent properties and flexible manufacturing capability, PDC is a promising technology to prepare ceramic fibers, coatings, composites and micro-sensors for high-temperature applications. However, the structure-property relationships of PDCs have not been well understood. The lack of such understandings drastically limited the further developments and applications of the materials. In this dissertation, the structure and properties of amorphous polymer-derived silicon carbonitride (SiCN) and silicoboron carbonitride (SiBCN) have been studied. The SiCN was obtained using commercially available polysilazane as pre-ceramic precursor, and the SiBCN ceramics with varied Si-to-B ratio were obtained from polyborosilazanes, which were synthesized by the hydroboration and dehydrocoupling reaction of borane and polysilazane. The structural evolution of polymer-derived SiCN and SiBCN ceramics from polymer to ceramics was investigated by NMR, FTIR, Raman, EPR, TG/DTA, and XRD. The results show a phaseseparation of amorphous matrix and a graphitization of “free” carbon phase, and suggest that the boron doping has a great influence on the structural evolution. The electric and dielectric properties of the SiCN and SiBCNs were studied by I-V curves, LCR Meter, and network analyzer. A new electronic conduction mechanism and structure model has been proposed to account for the relationships between the observed properties and microstructure of the materials. Furthermore, the SiBCN ceramics showed the improved dielectric properties at characterization iv temperature up to 1300 ºC, which allows the fabrication of ultrahigh-temperature wireless microsensors for extreme environments.

No description available.

Tesis por compendio / [EN] Sustainability is nowadays an investment for the future of any economic activity. The current situation of crisis has had an adverse impact in most industries, including the agri-food sector. However, this industry has been relatively the least affected when compared with other industrial sectors. This is mainly attributed to the fact that food products continue to be basic for consumers despite the economic downturn. Therefore, the agri-food sector is a key element in the European economy and can play a crucial role in the achievement of the objectives set in the EU's strategy for 2020: ensuring a sustainable framework of growth of a more competitive economy. The European agri-food industry has focused on energy efficiency and on reducing greenhouse gases emissions, along with better management of their resources as a way to improve its industrial competitiveness. In this sense, the search for solutions to transform the by-products generated in high value-added ingredients, is a priority. In this context, the juice industry, as fundamental sub-sector within the food sector, and large waste generator, must exploit the opportunity to transform their by-products into useful and profitable products for society. This transformation presents some difficulties which impede the profitability of the process. These difficulties are associated with the by-product, such as its compositional variability and its seasonality, and current techniques of transformation as the high energy cost in dehydration processes. This thesis represents an innovative and sustainable solution for overcoming the disadvantages associated with the high costs of stabilization, turning this by-products into high value-added ingredients, from both, nutritional and technological, points of view. The aim is to develop a microwave coupled with hot air drying technique allowing maximizing profits by using the following strategy: reducing time and operational costs, producing a new ingredient rich in dietary fiber, with interesting technological properties for the development of healthy foods, studying the proposed comprehensive process and analyzing the new generated by-products. The methodological approach of the thesis been focused, on the one hand, on studying phenomena that govern the internal transport of water and energy through the orange peel during its dehydration applying thermodynamics. On the other hand, the energy consumption of the drying process, the technological and sensory properties of the fiber obtained and its potential use as a fat substitute have been compared with the conventional hot air drying method. Finally, the integrated process, including both the combined drying technique and the pretreatments needed for colour and bitter compounds extraction, is proposed as a new route of valorization, in which the new by-products obtained, polyphenols and carotenoid rich extracts, are analysed. This study has analyzed the microwave coupled with hot air process, developing tools that allow the adequate upscaling of the drying operation by adapting it to the best standards of quality of the final product. A monitoring system that ensures these standards has been designed. The quality and the energy consumption of the dietary fiber production process has been improved. The properties associated with its inclusion in food matrices have been optimized. An innovative and sustainable process for the stabilization of industrial by-products and for their further conversion into dietary fiber and other bioactive compounds, applying microwave coupled with hot air drying, has been developed. / [ES] La sostenibilidad es una de las apuestas de futuro en cualquier actividad económica. La situación de crisis ha tenido un impacto adverso en la mayoría de las industrias, incluyendo las de ámbito agroalimentario. Sin embargo, ésta ha sido relativamente la menos afectada cuando se compara con otros sectores industriales. Esto se atribuye al hecho de que los productos alimenticios continúan siendo básicos para los consumidores a pesar de la desaceleración económica. Por lo tanto, esta industria es un pilar fundamental en la economía europea y puede jugar un papel crucial en la consecución de los objetivos marcados en la Estrategia de la UE para 2020: asegurar un marco sostenible de crecimiento de una economía más competitiva. La industria agroalimentaria europea ha apostado por la eficiencia energética y la reducción de emisiones de gases invernadero, junto con una mejor gestión de sus recursos como vía para la mejora de su competitividad industrial. La búsqueda de soluciones para transformar los subproductos generados en ingredientes de alto valor añadido, es una de las prioridades. En este contexto, la industria productora de zumos, como subsector fundamental dentro del sector alimentario, y gran generador de residuos, tiene la oportunidad de transformar sus subproductos en productos útiles y rentables para la sociedad. Esta transformación presenta algunas dificultades que impiden la rentabilidad del proceso. Estas dificultades están asociadas al subproducto, como su variabilidad composicional o su estacionalidad, y a las técnicas actuales de transformación como el elevado coste energético en procesos de deshidratación. Esta tesis se plantea como una solución innovadora y sostenible para, más allá de superar los inconvenientes asociados a los altos costes de estabilización, transformar este subproducto en un ingrediente de alto valor añadido, tanto nutricional como tecnológico. Para ello se propone desarrollar una técnica de secado combinado por aire caliente y microondas que permita maximizar beneficios mediante la siguiente estrategia: reducir el tiempo y el coste energético de la operación, produciendo un nuevo ingrediente rico en fibra dietética con propiedades tecnológicas de interés para el desarrollo de alimentos más saludables, estudiando el proceso integral propuesto y analizando los nuevos subproductos generados. El enfoque metodológico de la tesis ha estado dirigido, por una parte, a estudiar los fenómenos que gobiernan el transporte interno de agua y energía a través de la piel de naranja durante su deshidratación, aplicando termodinámica. Por otra parte, el consumo energético del proceso de secado, las propiedades tecnológicas y sensoriales de la fibra obtenida y su potencial uso como ingrediente sustituto de grasa, se han comparado con el método de secado convencional por aire caliente. Finalmente, el proceso integrado, incluyendo tanto el secado combinado como las etapas previas de extracción de color y compuestos amargos, se propone como una nueva ruta de valorización, en la que se analizan posibles subproductos de interés tales como extractos ricos en polifenoles y carotenoides. En este estudio se ha analizado el proceso combinado de secado con aire caliente y microondas, desarrollando herramientas que permiten dimensionar adecuadamente la operación de secado adaptándola a los estándares óptimos de calidad del producto final. Se ha diseñado un sistema de monitorización que asegure dichos estándares. Se ha mejorado el proceso de obtención de fibra alimentaria respecto a su calidad y a su gasto energético. Se han optimizado las propiedades asociadas a su inclusión en matrices alimentarias. Se ha desarrollado un proceso innovador y sostenible para la estabilización de subproductos vegetales de origen industrial y para su posterior conversión en fibra dietética y otros compuestos bioactivos, aplicando la tecnología de secado por aire caliente y / [CA] La sostenibilitat és una de les apostes de futur en qualsevol activitat econòmica. L'actual situació de crisi ha tingut un impacte advers en la majoria de les indústries, incloent les d'àmbit agroalimentari. No obstant això, la indústria agroalimentària ha sigut relativament la menys afectada quan es compara amb altres sectors industrials. Açò s'atribuïx principalment al fet de que els productes alimentaris continuen sent bàsics per als consumidors a pesar de la desacceleració econòmica. Per tant, esta indústria és un pilar fonamental en l'economia europea i pot jugar un paper crucial en la consecució dels objectius marcats en l'Estratègia de la UE per a 2020: assegurar un marc sostenible de creixement d'una economia més competitiva. La indústria agroalimentària europea ha apostat per l'eficiència energètica i la reducció d'emissions de gasos d'efecte hivernacle, junt amb una millor gestió dels seus recursos com a via per a la millora del seu vaig competirtu En este sentit, la busca de solucions per a transformar els subproductes generats en ingredients d'alt valor afegit, és una de les prioritats. En este context, la indústria productora de sucs, com subsector fonamental dins del sector alimentari, i gran generador de residus, té el deure i l'oportunitat de transformar els seus subproductes en productes útils i rendibles per a la societat. Esta transformació presenta algunes dificultats que impedixen la rendibilitat del procés. Estes dificultats estan associades al subproducte, com la seua variabilitat composicional o la seua estacionalitat, i a les tècniques actuals de transformació com l'elevat cost energètic en processos de deshidratació. Esta tesi es planteja com una solució innovadora i sostenible per a, més enllà de superar els inconvenients associats als alts costos d'estabilització, transformar este subproducte en un ingredient d'alt valor afegit, tant nutricional com tecnològic. Per a això es proposa desenvolupar una tècnica de'assecat combinat per aire calent i microones que permeta maximitzar beneficis per mitjà de l'estratègia següent: reduir el temps i el cost energètic de l'operació, produint un nou ingredient ric en fibra dietètica amb propietats tecnològiques d'interés per al desenvolupament d'aliments més saludables, estudiant el procés integral proposat i analitzant els nous subproductes generats. L'enfocament metodològic de la tesi ha estat dirigit, d'una banda, a estudiar els fenòmens que governen el transport intern d'aigua i energia a través de la pell de taronja durant la seua deshidratació, aplicant termodinàmica. D'altra banda, el consum energètic del procés de d'assecat, les propietats tecnològiques i sensorials de la fibra obtinguda i el seu potencial ús com a ingredient substitut de greix, s'han comparat amb el mètode d'assecat convencional per aire calent. Finalment, el procés integrat, incloent tant l'assecat combinat com les etapes prèvies d'extracció de color i compostos amargs, es proposa com una nova ruta de valoració, en la que s'analitzen possibles subproductes d'interés com ara extractes rics en polifenoles i carotenoides. En este estudi s'ha analitzat el procés combinat d'assecat amb aire calent i microones, desenvolupant ferramentes que permeten dimensionar adequadament l'operació d'assecat adaptant-la als estàndards òptims de qualitat del producte final. S'ha dissenyat un sistema de monitorització que assegure els dits estàndards. S'ha millorat el procés d'obtenció de fibra alimentaria respecte a la seua qualitat i al seu consum energètic. S'han optimitzat les propietats associades a la seua inclusió en matrius alimentàries. S'ha desenvolupat un procés innovador i sostenible per a l'estabilització de subproductes vegetals d'origen industrial i per a la seua posterior conversió en fibra dietètica i altres compostos bioactius, aplicant la tecnologia d'assecat por aire calent i microones. / Talens Vila, C. (2015). DESARROLLO DE TÉCNICAS COMBINADAS DE SECADO CON AIRE CALIENTE Y MICROONDAS EN LA PRODUCCIÓN DE FIBRA ALIMENTARIA A PARTIR DE SUBPRODUCTOS CÍTRICOS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54114 / Compendio

No description available.

La vitrification des déchets nucléaires de hautes activités est une étape importante à maîtriser afin d’assurer leur confinement. Depuis 2010, un procédé de vitrification en creuset froid présentant de nombreux avantages est exploité à cet effet dans l’usine de La Hague. Cette technologie est basée sur la circulation de courants électromagnétiques directement dans la charge du creuset dont les parois sont refroidies. Grâce au gradient thermique créé entre ces parois refroidies et le bain de verre en fusion, une couche de verre solide appelée autocreuset est formée jouant le rôle de barrière anticorrosive et électriquement isolante. Du fait de leur composition et de leur microstructure complexes, l’étude des propriétés électriques et diélectriques des verres d’intérêt nucléaire et la compréhension des phénomènes mis en jeu sont nécessaires afin de maîtriser convenablement le fonctionnement du procédé en creuset froid ainsi que les simulations thermo-hydrauliques qui lui sont associées.L’étude présentée ici porte sur la description des phénomènes de mouvements de charges électriques à l’origine des propriétés électriques et diélectriques ayant lieu au sein de verres borosilicatés d’intérêt nucléaire. Des relations entre ces propriétés et la composition ainsi que la microstructure de ces verres sont également établies. Ces problématiques sont tout d’abord abordées dans le cas de deux verres technologiques inactifs de compositions complexes grâce à des caractérisations microstructurales et des mesures d’impédance complexe à l’état solide. Une description plus détaillée des phénomènes mis en jeu est réalisée grâce à la caractérisation de verres simplifiés à 5 oxydes (SiO2-B2O3-Na2O-CaO -RuO2 ou -MoO3) permettant ainsi une meilleure compréhension des mouvements de charges selon la fréquence du champ électrique, la température ainsi que la composition et la microstructure du matériau. / The vitrification of high-level nuclear waste is an important step to master in order to ensure their immobilization. Since 2010, a cold crucible induction melter is used in the La Hague plant due to its advantages. This process is based on electromagnetic currents directly induced on the load of the crucible whose walls are water-cooled. Thanks to the thermal gradient established between these cooled walls and the molten glass, a solid glass layer called self-crucible is created which protects the crucible from corrosion effects and acts as an electrical insulator. Due to their complex composition and microstructure, the study of electrical and dielectric properties of nuclear glasses and the understanding of the related phenomena are necessary in order to efficiently master the cold crucible process and the associated thermo-hydraulic simulations.This study is dealing with the description of the electric charge motion phenomena involving the electrical and dielectric properties of the nuclear borosilicate glasses. Relationships between these properties, the composition and the microstructure are also given. These issues are firstly broached through the investigation of two industrial inactive glasses of complex composition thanks to microstructure characterizations and complex impedance measurements in the solid-state. A more detailed description of the phenomena is performed thanks to the characterization of simplified glasses containing 5 oxides (SiO2-B2O3-Na2O-CaO -RuO2 or -MoO3) allowing a better understanding of the charge motion according to the electrical field frequency, the temperature, the composition and the microstructure of the material.

Les matériaux ferroélectriques présentant une permittivité diélectrique élevée et de faibles pertes diélectriques présentent un grand intérêt pour la réalisation de condensateurs et le stockage de l'énergie électrique. Les propriétés structurales et diélectriques influencent les paramètres ferroélectriques tels que la polarisation maximale du matériau Pm et la polarisation rémanente Pr sous l'effet d'un champ électrique appliqué Em. Ce mémoire propose d'étudier les propriétés structurales, diélectriques et ferroélectriques des céramiques dérivées de BaTiO₃ (BT) et SrTiO₃ (ST) ainsi que des films épais PVDF pur et composites tels que PVDF/BT et PVDF/BZT. Les céramiques ont été synthétisées par la méthode de la réaction solide et le procédé sol-gel. La substitution dans les sites-A ou les sites-B du matériau BaTiO₃ avec des cations tels que Ca ²⁺, Sr²⁺ and Zr⁴⁺ réduit la densité d'énergie électrique stockée Wd et augmente l'efficacité de stockage énergétique η. La céramique BaZr₀.₅Ti₀.₅O₃ (BZT0.5) présente l'efficacité de stockage énergétique la plus élevée (η=75%). La substitution dans les sites-A du matériau SrTiO₃ avec 40% de cations Ca²⁺ diminue la permittivité diélectrique (ε'∽200), mais cette permittivité est cependant plus stable sur une large gamme de fréquence [100 Hz-1 GHz]. La céramique Sr₀.₆Ca₀.₄TiO₃ préparée par voie sol-gel présente la densité d'énergie électrique stockée la plus élevée (Wd=0.149 J/cm³) sous l'action d'un champ électrique maximal élevé (Em=105 kV/cm). Les films épais à base de polymère PVDF ont été synthétisés par Spin-Coating. La permittivité diélectrique des films épais PVDF pur augmente avec l'apaisseur du film. L'incorporation de particules BT et BZT0.15 dans la matrice polymère PVDF augmente la permittivité diélectrique des films composites PVDF/BT (ε'=32 pour 30% de particules BT) et PVDF/BZT0.15 (ε'=32 pour15% de particules BZT). / Ferroelectric materials with a high dielectric permittivity and low dielectric losses are very attractive for the realization of capacitors and for electrical energy storage. To improve the electrical energy density Wd, the structural and dielectric properties influence the ferroelectric parameters such as the maximum polarization Pm and the remanent polarization Pr under an applied electric field Em. This manuscript proposes to study the structural, dielectric and ferroelectric properties of ceramics derived from BaTiO₃ (BT) and SrTiO₃ (ST) as well as pure PVDF thick films and composites such as PVDF/BT and PVDF/BZT. The ceramics were synthesized by the solid state reaction reaction route and the sol-gel process. The subsitution in the A-sites or B-sites of the BaTiO₃ material with cations such Ca²⁺, Sr²⁺ and Zr⁴⁺ reduces the electrical energy density Wd and increases the energy storage efficiency η. The ceramic BaZr₀.₅Ti₀.₅O₃ (BZT0.5) has the highest energy storage efficiency (η=75%). The substitution in the A-sites of SrTiO₃ material with 40% of Ca²⁺ cations reduces the dielectric permittivity (ε'∽200), but is more stable over a wide frequency range [100 Hz -1 GHZ]. The Sr₀.₆Ca₀.₄TiO₃ ceramic prepared by sol-gel process has the highest electrical energy density (Wd = 0.149 J/cm³) under an electrical field Em = 105 kV/cm. The PVDF thick films were synthesized by Spin-Coating. The dielectric permittivity of pure PVDF thick films increases when increasing the thickness. The addition of BT and BTZ0.15 particles in the PVDF polymer matrix increases the dielectric permittivity of the composite PVDF/BT thick films (ε'=32 for 30% of BT particles) and PVDF/BZT0.15 ones (ε'=32 for 15% of BZT particles).

Metal oxides crystallized in perovskite structure are generally modified in two different ways. According to the general structural formula ABO3, the two ways are A-site modification and B-site modification. The primary significance of perovskite metal oxides rests on their importance in electronic devices. A particular class of perovskites, namely Lead Zirconate or modified Lead Zirconate has received a special attention because of their unique antiferroelectricity and various applications in devices. Among the other modifications, A-site modification of PbZrO3 by La is rare and not much explored. Chapter 1 describes various applications of antiferroelectric thin films along with the synthesis and characterization of pure and La modified PbZrO3, which are relevant to the work presented in this thesis. Sol-gel processing and spin coating technique to deposit solid oxide thin films are well known for their low cost of deposition as well as for their ability to achieve better stoichiometric chemical composition. Common crack formation problem of sol-gel grown films can be prevented by ‘drying control chemical adhesive’ like polyvinylpyrrolidone (PVP). Heat treatment of sol-gel derived thin films is generally determined by TGA and DTA. Crystalline phase of deposited solid thin films is determined by XRD whereas effect of modification can be ascertained by XRD peak assignment and relative crystalline peak shifting. Sol-gel grown film thickness is measured by common cross sectional SEM whereas AFM can detail the surface morphology. Chapter 2 summarizes the deposition and characterization of pure and La modified PbZrO3 thin films. Any nonmetal, which is insulator, is dielectric material and show dielectric dispersion in a frequency domain of low field alternative current. Among the most common feature of dielectric dispersion, Maxwell – Wagner type dispersion is well known. Similar kind of dielectric dispersion, named Maxwell – Wagner like dispersion, can be observed while the equivalent circuit consists of parallel G – C along with a series R. Universal power law of ac conductivity is the deciding factor to distinguish the nature of dispersion. Structural phase transition can be determined by dielectric response and it is widely known as dielectric phase transition. Effect of La modification on dielectric phase transition of PbZrO3 thin films depends on stabilization or destabilization of antiferroelectricity. Maximum dielectric constants of pure and modified PbZrO3 thin films depend on the crystallographic orientations of the growth. Chapter 3 presents dielectric properties of pure and La modified PbZrO3 thin films and these properties are correlated to the stabilization or destabilization of antiferroelectricity, relative integrated intensity of (202)O film orientation and trapped electron charge due to oxygen vacancies. Charge storage property of a capacitor is determined by the polarization of the capacitor on application of electric field whereas field dependent integrated area of polarization on withdrawal of electric field determines the recoverable capacitive energy storage. Among the three kinds of capacitors like linear or paraelectric, ferroelectric and antiferroelectric capacitors, antiferroelectric capacitor is known to be best for their ability to store huge amount of recoverable energy. The recoverable energy in antiferroelectrics can be increased by increasing squareness of the P – E hysteresis loop, applicable electric field, polarization or by the all possible combinations of them. Chapter 4 describes the correlation of relative integrated intensity of (202)O [RI(202)O] with critical applied electric field of P – E saturation to provide enhanced squareness of the hysteresis loops. This chapter also describes the variation of charge and recoverable energy storage properties with respect to RI(202)O. Like magnetocaloric effect, electrocaloric effect is capable to alter the temperature of a system by adiabatic polarization or depolarization. From the Maxwell’s relation of thermodynamics, assuming, (∂p ) = (∂s )electrocaloric effect can be calculated from temperature dependent polarization value of a paraelectric, ferroelectric or an antiferroelectric. Chapter 5 presents the electrocaloric effect of pure and La modified PbZrO3 thin films. Summary of present study and discussion have been delineated in Chapter 6 along with the future work which can give more insight into the understanding of antiferroelectric PbZrO3 thin films with respect to Pb and Zr site modification and with respect to different electrodes. (For formulas pl see the pdf file of the thesis)

High dielectric constant materials are of technological importance as they lead to the miniaturization of the electronic devices. In this context, the observation of anomalously high dielectric constant (>104) in the body-centered cubic perovskite-related (Space group Im3) material Calcium Copper Titanate ((CaCu3Ti4O12)(CCTO)) over wide frequency (100 Hz – 1MHz at RT) and temperature (100 – 600 K at 1 kHz ) ranges has attracted a great deal of attention. However, high dielectric constant in CCTO is not well understood yet, though internal barrier layer capacitor (IBLC) mechanism is widely been accepted. Therefore, the present work has been focused on the preparation and characterization of CCTO ceramic and to have an insight into the origin of high dielectric constant. Influence of calcination temperature, processing conditions, microstructure (and hence grain size), composition, doping etc on the electrical characteristics of CCTO ceramics were investigated. Electrical properties were found to be strongly dependent on these parameters. The dielectric constant in CCTO was observed to be reduced considerably on substituting La+3 on Ca+2 site. The formation temperature of CCTO was lowered substantially (when compared to conventional solid-state reaction route) by adopting molten-salt synthesis. The dielectric loss in CCTO was reduced by incorporating glassy phases at the grain boundary. Potential candidates for the practical applications such as charge storage devices, capacitors etc, with dielectric constant as high as 700 at 300 K was accomplished in a three-phase percolative composite fabricated by incorporating Aluminium particle into CCTO-epoxy composite. Polycrystalline CCTO thin films with dielectric constant as high as ~ 5000 (1 kHz and 400 K) were fabricated on Pt(111)/Ti/SiO2/Si substrates using radio frequency magnetron sputtering. Effect of sintering conditions on the microstructural, ferroelectric and varistor properties of CCTO and LCTO ceramics belonging to the high and low dielectric constant members of ACu3M4O12 family of oxides were investigated in detail and are compared. Ferroelectric-like hysteresis loop (P vs E) and weak pyroelectricity were observed in CCTO and plausible mechanisms for this unusual phenomenon have been proposed.