Effects of Sintering Atmosphere on Piezoelectric Properties of 0.75BF-0.25BT Ceramic

0.75BF-0.25BT ceramics were prepared by sintering at 980 - 1040 degrees C in air or under atmosphere powder. A sample with 1 mole %-excess Bi2O3 was also prepared to compensate for Bi2O3-evaporation. Physical and piezoelectric properties of these three samples were compared. When the sintering temperature increased from 980 degrees C to 1040 degrees C, the density of the sample sintered in air decreased continuously due to Bi-evaporation. Due to the suppression of Bi-evaporation, the sample sintered under atmosphere powder had a higher density at sintering temperatures above 1000 degrees C than did the sample sintered in air. The addition of 1 mole %-excess Bi2O3 successfully compensated for Bi-evaporation and kept the density at the higher value until 1020 degrees C. Grain size increased continuously when the sintering temperature increased from 980 to 1040 degrees C, irrespective of the sintering atmosphere. When the sintering temperature increased, the piezoelectric constant (d(33)) and the electromechanical coupling factor (k(p)) increased for all samples. The sample with 1 mole % excess-Bi2O3 showed the highest density and the best piezoelectric properties at sintering temperature of 1020 degrees C.