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.

Piezophotonics is a great interesting field of physics that has led to a number of important technologies, such as light source, smart sensors, and mechatronics. In this work, we reported Pr-doped (Bi_0·5Na_0.5)TiO₃-based lead-free ceramics with strong red photoluminescence emission and large strain response (d₃₃* = 460 pm/V, S = 0.32 %). The PL emission can be quenched by decreasing the intensity by 93 % after electrical polarization (E = 50 kV/cm). The local structure and electric field-induced structural changes were systematically investigated to reveal the significant distinction in photoluminescence properties caused by electrical polarization. The results indicated that polarization treatment eliminates the structural inhomogeneities and establishes a long-range ferroelectric tetragonal and rhombohedral distortion. The crystal structure transformed irreversibly from a non-ergodic to a normal ferroelectric state. PL quenching originated from the decreased distortion of octahedral due to the transition from a non-ergodic state to a highly ordered symmetrical structure. Meanwhile, the enlarged domain structure contributed to the photoluminescence quenching effect. Our findings demonstrate that an electric field can be a robust tool for adjusting the photoluminescence property and provide insights into the relationship between the structure and PL properties of BNT-based ceramics under an external stimulus.

In this paper, Sm-doped 0.96(K_0.48Na_0.52)(Nb_0.95Sb_0.05)–0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃ (abbreviated as KNSN–0.04BNKZ) lead-free piezoelectric ceramics were prepared by conventional solid-state sintering method and the effects of Sm₂O₃ on the phase structure, microstructure, electrical and luminescent properties of KNSN–0.04BNKZ potteries were studied. Results revealed that a single solid solution phase with pseudo-cubic perovskite structure was formed between KNSN–0.04BNKZ and Sm₂O₃. Existence of weak dielectric/ferroelectric properties with a diffuse dielectric anomaly and slim P–E hysteresis loops of the Sm-doped KNSN–0.04BNKZ demonstrated the ferroelectric relaxor behavior of the KNNS–0.04BNKZ–xSm ceramics. Accordingly, the temperature stability and fatigue behavior of the modified ceramics were significantly improved. It was found that the KNSN–0.04BNKZ ceramics with 0.002 mol Sm addition exhibited nearly temperature independent properties and fatigue-free behavior. Moreover, Sm-modified KNSN–0.04BNKZ exhibits a bright photoluminescence with a strong orange emission under visible light irradiation. As a material with both electrical and luminescent properties, it has good application prospect in future optoelectronic components by integrating its luminescent and electrical properties.