Textured high Curie point piezoelectric ceramics prepared by spark plasma sintering

Abstract

The Curie point T_c of ferroelectrics sets the upper temperature limit for their application as piezoelectrics. Some Aurivillius phase and perovskite-like layer structured (PLS) materials are good candidates for high temperature piezoelectric applications because of their high T_c. The Aurivillius phase CaBi₂Nb₂O₉ and PLS Sr₂Nb₂O₇ were densified by ordinary sintering and/or spark plasma sintering (SPS). All of the materials were single phase, and their grains were plate-like. Their density was >95%. The spark plasma sintered ceramics had grain oriented, textured microstructures. The Curie point of CaBi₂Nb₂O₉ was measured as 943±5°C. Ferroelectric switching in CaBi₂Nb₂O₉ was observed at room temperature. The d₃₃ of the textured CaBi₂Nb₂O₉ materials was nearly three times that of ordinary sintered materials. The Curie point of Sr₂Nb₂O₇ was measured as 1327±5°C. Ferroelectric and piezoelectric (2·8 pC N⁻¹) properties were observed for spark plasma sintered textured Sr₂Nb₂O₇ ceramics.