Microstructure, structure and electrical and dielectric properties of ZnO-doped K0.5Na0.5NbO3 (KNN) ceramics were investigated. Powders were obtained by the conventional solid-state method. Samples doped with 0 to 1 mol% of ZnO were sintered at 1125 °C for 2 h. Through XRD spectra, the perovskite structure was detected, in addition to small peaks corresponding to secondary phases. It was also observed that zinc changed the microstructure and grain size of KNN ceramics. The addition of 0.5 mol% of Zn2+ produced a softening effect in the ferroelectric properties of the material, and increased its final density. Conversely, the addition of 1 mol% of Zn2+ reduced the sample densification.

The influence of Fe3O4 and BaTiO3 on dielectric and magnetic properties of Fe3O4/BaTiO3/epoxy composites was studied. Initially, biphasic Fe3O4/epoxy and BaTiO3/epoxy composites were analyzed, and based on these results Fe3O4/BaTiO3/epoxy composite were conformed. In all the cases, dielectric properties were influenced by the frequency and filler concentration. In this way, Fe3O4/epoxy composites with high filler concentration showed high dielectric loss due to percolation effects and semiconducting properties of Fe3O4.

Con el objetivo de estudiar nuevos materiales multipropósito, en este trabajo se analizó la influencia de las partículas de Fe3O4 y BaTiO3 sobre las propiedades magnéticas y dieléctricas de los sistemas Fe3O4/BaTiO3/epoxi. A tal efecto se analizaron los sistemas bifásicos Fe3O4/epoxi y BaTiO3/epoxi y a partir del análisis de los resultados se conformaron los compuestos Fe3O4/BaTiO3/epoxi. En todos los casos los valores de permitividad y pérdidas dieléctricas fueron altamente influenciados por el contenido de carga. En este sentido, los materiales procesados con Fe3O4 presentaron muy elevadas pérdidas dieléctricas para altas concentraciones de carga debido a efectos de percolación y a las propiedades semiconductoras del Fe3O4.

Integral capacitors (IC) of one or two-layer printed wiring board (PWB) circuits were produced using comb electrodes fixtures and dielectric composites as the inter-electrode material. ICs were fabricated at laboratory scale, using copper comb electrodes and BaTiO3-epoxy composite materials deposited on a glass-Epoxy FR4 board. They were experimentally tested in order to obtain their electrical response. Furthermore, ICs behaviour was modelled through 2-dimensional models applying finite element method (FEM). Results showed that by this laboratory technique it was possible to obtained integral capacitors with low dielectric losses. Moreover, acceptable agreement was found between numerical and experimental capacitance results for all the different analysed ICs. In conclusion, 2D FEM models are a suitable tool to predict electric response of IC devices.

The dielectric behavior of composite materials (epoxy resin - barium titanate and epoxy - CCTO) was analysed as a function of ceramic amount. Composites were prepared by mixing the components and pouring them into suitable moulds. In some compositions, the matrix was reduced by tetrahydrofuran (THF) incorporation. Samples containing various amounts of ceramic filler were examined by TG/DTA and scanning electron microscopy analysis. Dielectric measurements were performed from 20 Hz to 1 MHz and 30 to 120 °C. It was demonstrated that the epoxy - CCTO composites possessed higher permittivity than classic epoxy - BaTiO3 composites. However, the low resin permittivity prevailed in the composite dielectric performance.