Textured Lead-Free Ceramic with High Thermal Stability and Electrical Quality Factor

A major challenge with (K,Na)NbO₃ compositions is maintaining high piezoelectric figures of merit (FOM) in a wide range of temperatures and electric fields. A textured composition is demonstrated, K_0.48Bi_0.02Na_0.5Nb_0.92Sb_0.04Zr_0.04O₃ incorporating 3 wt.% NaNbO₃ templates, that exhibits a d₃₃ of 570 pC/N and k₃₁ of 0.4 at room temperature. Additionally, a high texture degree of ≈98% is achieved with the desired microstructural orientation. Electrical quality factor (Q_e  =  1/tan δ) is effectively improved from 22 to 33 with 0.1 mol% MnO₂ doping. The strain response (S_max/E_max) is calculated to be 450 pm V^-1 under 40 kV cm^-1, and P-E and S-E loops exhibited excellent fatigue resistance up to 10⁶ cycles. To validate the practical relevance, the energy harvesting performance is explored under both on-resonance and off-resonance conditions using vibration velocity measurement and a cantilever type energy harvester, respectively. The maximum output power recorded is ≈50 µW with a volume power density of ≈2 µW mm^-3. The vibration velocity reached 0.26 m s^-1 under a drive voltage of 30 V mm^-1 at resonance. Through the combination of defect engineering (Mn doping) and microstructural engineering (texturing), the results confirm an excellent combination of electromechanical properties along with thermal stability and fatigue resistance in this material system.