LOCAL DISORDER IN THE STRUCTURE OF BA(TI,CE)O3 PEROVSKITE BY MEANS OF POWDER DIFFRACTION AND TOTAL SCATTERING. EFFECT OF TEMPERATURE, DOPING CONCENTRATION AND GRAIN SIZE.

Nowadays BaTiO3 is considered as one of the most relevant environmental-friend ferroelectric and, thank to the chemical substitutions at the Ba2+ and/or Ti4+ sites, its properties are usually tailor to meet a big variety of devices and performance requirements. A classical example is the solid solution BaTi1-xMIVxO3, where M could be Sn, Zr, Hf, Ce etc., whose ferroelectric behavior shows an almost continuous variation with composition. The study of these compounds is then essential to improve their characteristics and make their suitable in more applications. Considering that their properties are deeply linked to the structure and especially to structural defects, average and local structural analyses are essential to better understand the origins of different polar behaviours and to have a real control on these materials. Despite this need, only BaTi1-xZrxO3 (BTZ) system, which is one of the most popular dielectrics used in multilayer ceramic capacitors, has been investigated in some detail. Although the similarity to BTZ suggests that BaTi1-xCexO3 (BTC) may be promising as lead free actuator materials, studies on this solid solution are almost limited. Thus in this research the BTC solid solution has been structurally investigated in order to provide knowledge lacks. Different ceramic samples with different doping amounts and different polar behaviours (from normal ferroelecric to relaxor via diffuse phase transition) have been investigated at different temperatures. In addition, taking into account the current tendency in miniaturized devices required in microelectronics, also chemical equivalent nano powders have been considered to explore not only doping effects, but also that of size. Pair Distribution Function (PDF) with different type of approaches (as carbox, biphasic and so on) has been employed coupled with TEM analysis and Raman spectroscopy. A complete description of that BaTi1-xCexO3 materials is given underlining links between polar behaviours, temperature, doping and size effects.