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 o C in air or under atmosphere powder. A sample with 1 mole %-excess Bi 2 O 3 was also prepared to compensate for Bi 2 O 3 -evaporation. Physical and piezoelectric properties of these three samples were compared. When the sintering temperature increased from 980 o C to 1040 o 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 o C than did the sample sintered in air. The addition of 1 mole %-excess Bi 2 O 3 successfully compensated for Bi-evaporation and kept the density at the higher value until 1020 o C. Grain size increased continuously when the sintering temperature increased from 980 to 1040 o 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-Bi 2 O 3 showed the highest density and the best piezoelectric properties at sintering temperature of 1020 o C.