Fabrication of grain-oriented PbNb₂O₆-based high temperature piezoelectric ceramics

Grain-oriented Sr and Ti modified lead metaniobate (Pb_0.96Sr_0.04)Nb_1.96Ti_0.05O₆ (PSNT) ceramics with 4 mol% excess of Nb₂O₅ were prepared by templated grain growth method. The needle-like PSNT templates were obtained through the molten salt synthesis method. The effects of the template concentration (5, 10, 20 and 30 wt%) on the texture degree, microstructure, and electrical properties of textured ceramics were investigated. Improved electromechanical properties were found along the direction perpendicular to the sheet in textured PSNT ceramics, which shows the preferential orientation. An excess of templates would seriously deteriorate the properties of textured ceramics. The textured PSNT ceramics with 5 wt% templates exhibit high Curie temperature T_c of 545 °C, and improvement in piezoelectric coefficient d₃₃ by 9% (d₃₃ = 98 pC/N) and g₃₃ by 45% (g₃₃ = 42 × 10⁻³ Vm/N), as well as electromechanical coupling coefficient k₃₁ by 18% (k₃₁ = 0.26) compared to randomly oriented ceramics. The study demonstrates that grain-orientation controlling in PN-based ceramics is a potential way to improve the piezoelectric properties while maintaining high Curie temperature.