The effect of Li/Ce co-doping on structural and electrical properties of Sr_2-x(Li, Ce)_x/2Nb₂O₇ piezoelectric ceramics

As a typical perovskite-like layered structure (PLS) ceramic, Sr2Nb2O7 (SNO) possesses a high Curie temperature T-C value above 1300 degrees C, which is expected to work in higher temperature environment. However, pure SNO presents a piezoelectric constant d(33) value of similar to 1 pC/N. Hence, (Li, Ce) ions are doped in SNO ceramics, which increases the distortion of oxygen octahedrons and enhances the intrinsic contribution of piezoelectric properties. The increased domain size with large proportion of high response areas means that the extrinsic contribution is also improved. The introduction of (Li, Ce) ions can also promote ceramic's grain growth and reduce oxygen vacancies, leading to the improvement of electrical properties. The optimal component Sr-1.96(Li, Ce)(0.02)Nb2O7 ceramics exhibit a d(33) value of 3.1 pC/N, a higher resistivity of 1.65x10(6) Omegacm at 700 degrees C and an excellent thermal stability (a d(33) value of 3.0 pC/N after annealing at 1200 degrees C for 2 h). This work provides an effective approach with simple process and low cost for the application of PLS materials in high-temperature environments.