Effect of A site substitution on the properties of CaBi2Nb2O9 ferroelectric ceramics

The effect of A-site substitution on the piezoelectric coefficient, high-temperature dc resistivity, and thermal depoling behavior of Aurivillius phase CaBi2Nb2O9 ferroelectric ceramics was investigated. Ceramics with the general formula of Ca1-xMxBi2Nb2O9, where M=Na, (Na,Ce), (Na,La), and La, were prepared by conventional solid-state sintering. All the ceramics were single-phase ferroelectrics with high Curie points (similar to 900 degrees C). The doped ceramics, Ca0.9Na0.1Bi2Nb2O9, Ca-0.9(NaLa)(0.1)Bi2Nb2O9, Ca0.95La0.05Bi2Nb2O9, and Ca0.9La0.1Bi2Nb2O9, had improved resistance to thermal depoling compared with Ca2Bi2Nb2O9 and were stable up to 800 degrees C. The donor dopants increased the dc electrical resistivity, while the acceptor dopants decreased it. The donor-doped Ca0.95La0.05Bi2Nb2O9 had a higher piezoelectric constant (d(33)=12.8 pC/N) compared with CaBi2Nb2O9 (d(33)=5.8 pC/N), and its electrical resistivity was higher than 10(6) Omega(.)cm at 600 degrees C. These properties suggest that doped CaBi2Nb2O9 ceramics might be good candidates for high-temperature piezoelectric applications.