INVESTIGATION OF GRAIN-SIZE INFLUENCE ON THE FERROELECTRIC-TO-PARAELECTRIC PHASE-TRANSITION IN BATIO3 CERAMICS BY MEANS OF AC CALORIMETRY

Barium titanate ceramic samples of four different average grain sizes from 0.5 mu m to 20 mu m were studied hy means of the ac calorimetric method. The ferroelectric-to-paraelectric transition temperature decre ased with decreasing grain size. The temperature dependence of heat ca pacity showed hysteresis during a heating/cooling cycle. The thermal h ysteresis was found to be grain-size dependent. with a possible maximu m For grain sizes between 0.5 mu m and 2.5 mu m. The small shift of th e Curie temperature detected in these oc calorimetry experiments sugge sts that internal stresses are the main cause of:he observed grain-siz e effects.