Thermal Stability and Humidity Resistance of ScTaO₄ Modified (K_0.5Na_0.5)NbO₃ Ceramics

Lead-free (Na_0.5K_0.5)NbO₃-xmol% ScTaO₄ (x=0-1.5) ceramics are prepared using the conventional solid-state reaction method and their properties are investigated in detail. The results indicate that the piezoelectric properties and density are improved by the introduction of ScTaO₄. Due to the high orthorhombic-tetragonal phase transition temperature T_O-T (around 200°C), stable piezoelectric properties against temperature are obtained. In a wide temperature range of 15-160°C, k_p of the (Na_0.5K_0.5)NbO₃-0.5mol% ScTaO₄ ceramic remains almost unchanged and d₃₁ increases slightly from 59pC/N to 71pC/N. The deliquescent problem is effectively solved by the addition of ScTaO₄. The piezoelectric properties of ScTaO₄ modified (Na_0.5K_0.5)NbO₃ ceramics show no obvious reduction and dielectric loss increases slightly after 120h of immersion. From the analysis, it is suggested that the density is an important factor that improves the humidity resistance of the specimens.