Optimization of the piezoelectric and dielectric properties of BST-BCT ceramics obtained by mechanosynthesis
POYATO R. 1, OTERO A. 1,2, GOTOR F. 1, SAYAGUÉS M. 1, MORALES-RODRÍGUEZ A. 2, MORICHE R. 2
1 Instituto de Ciencia de Materiales de Sevilla, ICMS, CSIC-Universidad de Sevilla, Américo Vespucio 49, 41092, Sevilla, Spain , Seville, Spain; 2 Dept. de Física de la Materia Condensada, Universidad de Sevilla, Apdo. 1065, 41080, Sevilla, Spain , Seville, Spain
Solid solutions of x(BaSn0.12Ti0.88O3) – (1-x)?(Ba0.7Ca0.3TiO3) with different x values ranging from 0.4 up to 0.6 were obtained by mechanosynthesis. These values were selected pursuing the presence of morphotropic phase boundaries (MPBs). The ceramic powders were characterized by X ray diffraction and scanning and transmission electron microscopy. Pure phases were successfully achieved after 120 minutes of milling; only a small quantity of BaCO3 was detected, which was eliminated by heating the powder at 900 ºC/1h before the sintering process. The size of crystal domains and cell parameters were calculated by Rietveld refinement.
Consolidation of the powders was carried out by conventional and spark plasma sintering (CS and SPS) in order to optimize densification and elucidate the dependency of the properties on the microstructural features. Sintering temperature was in the range of 1400-1500 °C for dwell times of 4, 5 and 6 h for CS and 10 and 15 minutes for SPS.
The influence of the stoichiometry on the piezoelectric and dielectric properties was analyzed on the different sintered ceramics. Poling was conducted at different voltages and temperatures to set up the best parameters to maximize the piezoelectric coefficient (d33) value. The dielectric permittivity was measured as a function of the temperature to set the Curie temperature.