Achieving ultrahigh piezoelectric coefficient and good temperature stability in (K,Na)NbO3-based laminated ceramic composites

The (K,Na)NbO3-based ceramics are a promising type of lead-free piezoelectric material, but simultaneously achieving an ultrahigh piezoelectric coefficient d33 and good temperature stability in them is extremely difficult due to the phase transitions. An approach of fabricating the engineered piezoelectric materials of laminated ceramic composites (LCCs) was proposed to break the bottleneck instead. Two or more piezoelectric ceramic layers are stacked in the order of alternatively opposite polarizations and are combined together by electrodes, which are connected as in the cases of bimorph or laminated multilayer ceramic capacitors. Experimentally, a compositional series of (1 − x)(K0.48Na0.52)(Nb0.96Sb0.04)O3–x(Bi0.50Na0.50)ZrO3 (KNNS-xBNZ) ceramics and a textured 0.965(K0.48Na0.52)0.99Li0.01(Nb0.98Sb0.02)O3-0.035(Bi0.50Na0.50)ZrO3 (KNLNS-BNZ) ceramic were used to verify this approach. The four-layer LCC with thin ceramic plates of different KNNS-xBNZ compositions shows an averaged d33 of 1230 pC/N, and temperature stability of d33 changes within ±5% up to 120 °C. The three-layer LCC of KNLNS-BNZ textured ceramic exhibits d33 of 1100 pC/N at room temperature with d33 changes of less than 8.1% up to 190 °C. This work provides an innovative strategy to obtain some unprecedentedly piezoelectric materials with extraordinarily excellent performance thereby getting more possibilities in device applications.