RESEARCH AND DEVELOPMENT OF LEAD-FREE PIEZOELECTRIC CERAMIC MATERIALS

点击翻译按钮获取中文摘要

Recently, lead-free piezoelectric materials have been attracting attention as new materials in place of PZT materials for environments. Among of many lead-free piezoelectric materials, bismuth sodium titanate, (Bi_<1/2>Na_<1/2>)TiO_3 [BNT]-based and bismuth layer-structured ferroelectric ceramics will be a superior candidate. Bismuth layer-structured ferroelectrics (BLSF) are characterized by their low dielectric constant ε s, high Curie temperature, T c, and large anisotropy in electromechanical coupling factors k t/k p or k33/k31.In this research, Sr_<m-3+x>Bi_<4-x>Ti_<m-x>Ta_xO_<3m+3> (m=2, x=1〜2 ; m=3, x=0〜2) [SBTTm (x)] ceramics are studied on their ferroelectric and piezoelectric properties which are applied to lead-free piezoelectric devices. The SBTT3 (0.3) ceramic shows the strong ferroelectricity and high piezoelectricity. From the measurement of D-E hysteresis, the remanent polartzation, P r of SBTT3 (0. 3) was the largest (P r=12.3 μC/cm^2) in the SBTT3 (x) system and coercive field, E c of SBTT2 becomes larger with decreasing the amount of Ta concentration (x). The electromechanical coupling factor, k33 and piezoelectric constant, d33 of the grain oriented SBTT3 (0.3) ceramic were relatively high of k33=0.37 and d33=45.3 pC/N, respectively. The mechanical quality factor, Q m, of the SBTT2 (1.5) ceramic was very high of more than 8000. The SBTT ceramics seem to be a superior candidate for lead-free piezoelectric resonator or high temperature piezoelectric sensor materials.