Large strain response in lanthanide-doped potassium sodium niobate-based piezoceramics

Developing polymorphic phase coexistence near room temperature in potassium sodium niobate-based piezo-ceramics is a widespread way to improve strain performance. Herein, 0.97(K0.48Na0.52)1-3xLaxNbO3-0.03SrTiO3 piezoceramics were studied by analyzing their grain images, crystal structures, dielectric properties, Raman spectra, ferroelectric properties, strain responses, and piezoelectric properties. A high strain of 0.43% was achieved at x = 0.0050 presenting a diffuse phase transition state, due to various intrinsic factors, including large electrostriction, small piezoelectric effects, and extrinsic microdomain wall reorientation. The large electro-striction was the chief contribution to the strain due to the considerable electrostrictive coefficient (Q33) of 0.039 m4/C2. Furthermore, the considerable Q33 was due to B-site shifting by distorting the slightly compressed NbO6 octahedron arising from La3+ doping. The compressed of the NbO6 octahedra was proven by XRD results and generated distortion according to the obtained Raman spectra.