Microstructure and Electronic Properties of Medium-Entropy (Ba _1/3 Sr _1/3 Ca _1/3 )Bi ₂ Nb ₂ O ₉ Ceramic Powder with Enhanced Piezocatalytic Performance

Piezoelectric catalysis presents significant potential for addressing energy crises and environmental pollution. Medium-entropy (Ba_1/3Sr_1/3Ca_1/3)Bi₂Nb₂O₉ (BSCBN) piezoelectric ceramic powder was successfully prepared by the molten salt solid-state synthesis method, incorporating the concept of configurational entropy. Compared with pure CaBi₂Nb₂O₉ (CBN), the microstructure of mesoscopic entropy BSCBN remains unchanged, exhibiting a nanoplate morphology. However, the presence of lattice distortion (compression of the Bi-O layers and elongation of the BaSrCaNb-O layers) leads to a reduced band gap, enhanced electron delocalization, and an improved piezoelectric polarization response. Importantly, the BSCBN powder exhibits significantly enhanced RhB degradation ability, with a rate constant as high as 0.025 min^-1, which is about 5 times that of CBN. Meanwhile, the piezoelectric catalytic hydrogen production activity of BSCBN from pure water is about 2.3 times higher than that of CBN, with excellent stability and reusability. The improved piezocatalytic performance can be attributed to the lattice distortion induced by the medium-entropy strategy, which strengthens the polarization electric field and thereby facilitates more efficient separation and migration of charge carriers, ultimately leading to an extended carrier lifetime and a significant acceleration of the catalytic reaction process. This study provides a valuable paradigm for optimizing the performance of piezoelectric materials by entropy engineering.