Improved resistivity in bismuth deficient morphotropic phase boundary 0.88BNT-0.08BKT-0.04BT ceramics

Acceptor doping is used to achieve hard piezoelectric properties by inducing oxygen vacancies. In Bi0.5Na0.5TiO3 (BNT) based ceramics, modifying the A-site stoichiometry can be used to achieve similar effect as acceptor doping, such as bismuth deficiency that induces oxygen vacancies. In this work 0.88Bi0.50−xNa0.50TiO3 - 0.08Bi0.50−xK0.50TiO3 - 0.04BaTiO3 (BNKBT88-xBi) ceramics with bismuth deficiency x≥0.02 have been prepared. The Bi-deficient ceramics have low dielectric loss, high mechanical quality factor of 1200, and coercive field of 48kV/cm. However, at elevated temperature the mobility of oxygen vacancies decreases resistivity, limiting the use of these ceramics for high power transducer application. The addition of bismuth oxide to the calcined Bi-deficient compositions improves piezoelectric, dielectric, ferroelectric, and electrical properties at elevated temperature. Mechanical quality factor over 900 was achieved for small Bi2O3 addition.