No abstract

No abstract

Polarization field engineering of piezoelectric materials is considered as an advisable strategy in fine‐tuning photocatalytic performance which has drawn much attention recently. However, the efficient charge separation that determines the photocatalytic reactivities of these materials is quite restricted. Herein, a judicious combination of piezoelectric and photocatalytic performances of BiOX/BaTiO3 (X = Cl, Br, Cl0.166Br0.834) to enable a high piezophotocatalytic activity is demonstrated. Under the synergic advantages of chemical potential difference and piezoelectric potential difference in BiOX/BaTiO3 composites, the photoinduced carriers recombination is largely halted, which directly contributes to the significantly promoted piezophotocatalytic activity of piezoelectric composites. Inspiringly, the BiOBr/BaTiO3 composites under light irradiation with auxiliary ultrasonic activation result in an ultrahigh and stable photocatalytic performance, which is much higher than the total of those by isolated photocatalysis and piezocatalysis, and can rival current excellent photocatalytic system. In fact, the theoretical piezoelectric potential difference of BiOBr/BaTiO3 composites reaches 100 mV, which far exceeds the pure BaTiO3 of 31.21 mV and BiOBr of 30 mV, respectively. First, fabrication of BiOX/BaTiO3 piezoelectric composites and its remarkable piezophoto coupling catalysis behavior lays new ground for developing high‐efficiency piezoelectric photocatalysts in purifying wastewater, killing bacteria, and other piezophototronic processes.

No abstract

The 0.5 wt% MnO2‐doped 0.95(K0.5Na0.5)(Nb0.965Sb0.035)O3‐0.01CaZrO3‐0.04(Bi0.5K0.5)(Hf0.98Ti0.02)O3 (95KNNS‐1CZ‐4BKHT) lead‐free ceramics with grain size from 0.31 to 3.83 µm are fabricated by hot‐press sintering (HPS), microwave sintering (MS), conventional sintering (CS), two‐step sintering (TSS), and a combination of two of the above‐mentioned methods. Then, the grain size effects on the phase transition, electrical properties, domain structure, and temperature stability of the ceramics are investigated. The phase structure evolves from single rhombohedral (R) phase to coexisted rhombohedral‐tetragonal (R‐T) phases around 1 µm. The electromechanical properties are strongly grain size dependent. The values of piezoelectric coefficient (d33) and planar electromechanical coupling factor (kp) first rise sharply when the grain size is less than 1 µm, and then increase mildly in the grain size range from 2.55 to 3.04 µm and finally almost remain a constant (≈450 pC N−1 and 54%) when the grain size is larger than 3.31 µm. The R‐T phase coexistence and strip‐like nanodomain structure characterized by an easier switching feature contribute to the high piezoelectric and electromechanical properties of coarse‐grained samples. This work not only clarifies the relationship between grain size and electrical properties in KNN‐based ceramics, but also provides a novel strategy for developing high‐performance lead‐free piezoceramics.