Dynamic behavior of BiVO4 material under mechanical studies

The mechanical relaxation technique is applied to investigate the fundamental dynamic behavior of BiVO4 material. A prominent internal friction peak is observed around 430 K at 1 Hz, which is actually composed of three sub-peaks (P1, P2 and P3 from low to high temperature). And the associated modulus anomalies can also be found in any of the samples. The peak P1 with activation energy E1 ∼ 3.20 eV is probably related to the stress-induced unequal positions of Bi3+ ions; while the main P2 peak with E2 = 0.91 eV is associated with a complex mechanism, which originates from the viscous motion of domain walls and the interaction of domain walls with oxygen vacancies; and the responsive P3 peak is resulted from the ferroelastic-paraelastic phase transition, accompanied by a minimum modulus value. Based on the relaxation process and crystalline structure of BiVO4, the motion model of ferroelastic domain walls and transport mechanism of diffusion are suggested. Our results pave the way for better understanding the intrinsic dynamic and multifunctional properties of BiVO4.