Temperature stability, phase structure and electrical behavior of Li-modified 0.99(K0.48Na0.52)NbO3–0.01BiCoO3 piezoelectric ceramics

High temperature applications of piezoelectric ceramics require not only high Curie temperature (TC), but also good thermal stability in a wild temperature range. To achieve this goal, 0.99[(K0.48Na0.52)1−yLiy]NbO3–0.01BiCoO3 [KNLN-y-BC] piezoelectric ceramics have been prepared by a conventional solid-state sintering method. The effects of lithium on the phase structures, electrical properties, and thermal stability were investigated. A polymorphic phase boundary between orthorhombic and tetragonal phases has been found in the composition range of 0.02≤ y ≤0.03 at room temperature. With the increasing content of Li, TC gradually raised while TO–T reduced, respectively. The TO–T value of KNLN-0.03-BC ceramic is close to room temperature, resulting in good electrical properties (d33∼180, kp∼0.326). Moreover, KNLN-y-BC ceramics possess a lower TO–T and higher TC (>400 °C) when y≥0.03, that means they have a better thermal stability and might be used in a broader temperature range.