Extremely temperature-stable piezoelectric properties of orthorhombic phase in (K,Na)NbO3-based ceramics

Piezoelectric temperature stabilities are often a critical issue for many piezoelectric materials in practical applications. We report an important physical phenomenon recently discovered in a variety of (K,Na)NbO3-based ceramics. Piezoelectric properties are extremely temperature-stable in orthorhombic phase. No or only weak piezoelectric temperature dependence and excellent thermal aging stability are observed over considerably wide temperature intervals, which are broader than 325 °C in (K0.48Na0.52)NbO3 ceramic and 215 °C in (K0.50Na0.50)0.98Li0.02Nb0.82Ta0.18O3 ceramic, respectively. In general, the orthorhombic phase possesses much better piezoelectric temperature stabilities than the tetragonal phase. Thus, we suggest that future compositional designs of (K,Na)NbO3-based lead-free piezoelectric ceramics should take this phenomenon into full consideration.