Temperature-insensitive KNN-based ceramics by elevating O-T phase transition temperature and crystal texture

The inferior temperature stability of piezoelectric response is the main drawback of KNN-based ceramics. Here, the Ba-doped 0.97(K_0.48Na_0.52)(Nb_0.96Sb_0.04)O₃-0.03Ba_x(Bi_0.5Ag_0.5)_1-xZrO₃ (abbreviated as KNNS-BBAZ) textured ceramics were prepared by the template grain growth (TGG) method. Excellent comprehensive properties (d₃₃=(406 ± 15) pC/N, T_C = 274 ℃, strain is 0.17%) were achieved in KNNS-BBAZ textured ceramics with x = 0.2. Meanwhile, its piezoelectric and strain properties also show superior temperature stability (d₃₃ maintained within ±20% change in a wide temperature range from 25 ℃ to 200 ℃ and strain variation was less than 5% in the temperature range from room temperature to 165 ℃). The high O-T phase transition temperature (T_O-T is 110 ℃) induced by incorporating Ba ions accounts for the enhanced temperature stability of piezoelectric properties. In addition, the crystal texture always maintains the contribution of piezoelectric anisotropy to the piezoelectric properties during elevated temperature, which significantly improved the temperature stability of piezoelectric properties. This work provides an effective strategy for simultaneously achieving high piezoelectric response and excellent temperature stability in KNN-based ceramics.