Microstructure and electrical properties of ultra high temperature (1-x)CaBi2Nb2O9-xNa0.5Bi2.5Nb2O9 ceramics

Bismuth layer structured ferroelectric ceramics of (1-x)CaBi2Nb2O9-xNa(0.5)Bi(2.5)Nb(2)O(9) [(1-x) CBNO-xNBNO, 0 <= x <= 1.0] ceramics were obtained by conventional solid state reaction method. The effects of Na0.5Bi2.5Nb2O9 (NBNO) addition on the microstructure and electrical properties of ceramics have been studied. X-ray diffraction studies reveal that NBNO diffuses into the CBNO lattices to form a solid solution with an Aurivillius structure a pure orthorhombic space group A2(1)am. The room temperature record Raman spectra of CBNO-NBNO ceramics with x50.0-0.8, the well defined phonon modes around 190, 587 and 820 cm(-1) are observed. They were all single phase ferroelectrics with high Curie points (similar to 900 degrees C). Compared with CBNO, all the solid solution ceramics have a higher piezoelectric constant d(33), and a larger remnant polarisation (P-r). The 0.6CBNO-0.4NBNO ceramics possess the optimal piezoelectric properties, and the piezoelectric coefficient (d(33)), Curie temperature (T-c), and remanent polarisation 2P(r) were found to be 10.3 pC N-1, 903 degrees C and 5.0 mu C cm(-2) respectively. These properties suggest that CBNO-NBNO system ceramics might be good candidates for high temperature piezoelectric applications.