Electromechanical Properties of Lead Titanate Zirconate Ceramics Modified with Certain Three‐or Five‐Valent Additions

Abstract

When small amounts of lanthana, neodymia, niobia, or tantala are added to lead titanate zirconate compositions near the morphotropic (rhombohedral‐tetragonal) phase boundary, the modified ceramics show piezoelectric planar coupling coefficients of about 0.50 and substantially increased dielectric constants of up to 1545. The mechanical Q factor is decreased to about 70, and there is a marked increase in volume resistivity at temperatures up to 500°C. Other effects noted are better shelf‐aging characteristics, improved stability with respect to temperature dependence of resonant frequency, and a lowering of the Curie temperature. Except with neodymia, a definite refinement of the grain structure is also observed. By similar modification of Pb 0.95 Sr 0.05 (Zr. 0.54 Ti 0.45 )O 3 dielectric constants up to 1792 are obtained along with planar couplings of at least 0.49.