Good high-temperature stability and improved piezoelectric properties of (K_0.5Na_0.5)NbO₃–Bi(Mg_0.5Zr_0.5)O₃ ceramics

(1−x)(K_0.5Na_0.5)NbO₃–xBi(Mg_0.5Zr_0.5)O₃ (abbreviated as KNN–BMZ) [x = 0, 0.005, 0.0075, 0.01, 0.015, 0.02] solid solution ceramics were fabricated by an ordinary ceramic sintering technique. The piezoelectric and dielectric properties of ceramics were enhanced significantly through adding Bi(Mg_0.5Zr_0.5)O₃. X-ray powder diffraction analysis certified that the Bi(Mg_0.5Zr_0.5)O₃ has diffused into (K_0.5Na_0.5)NbO₃ to form a new perovskite structure solid solution. The addition of Bi(Mg_0.5Zr_0.5)O₃ depressed the orthorhombic–tetragonal phase transition temperature from 205 to 136 °C and tetragonal–pseudocubic phase transition temperature (Curie point) from 419 to 397 °C. Furthermore, the ceramics exhibited higher relative permittivity and lower dielectric loss than the pure (K_0.5Na_0.5)NbO₃. Especially, when x = 0.0075, the ceramics showed the improved high relative permittivity (ε ~2024), low dielectric loss (tanδ <3.8%) and thermal stability (Δε/ε_143°C ≤ ±10%) over a wide temperature range (143–337 °C). Moreover, when x = 0.005, the piezoelectric constant was improved to d ₃₃ = 118 pC/N. These results indicated that the BMZ added ceramics have potential applications in piezoelectric and thermal stability devices.