Origins of dielectric relaxations in AgNb7O18 ceramic

The origins of the relaxor behavior and low-temperature dielectric relaxation processes in AgNb7O18 ceramic were studied and a new relaxation mechanism was proposed through combined bond valence energy landscape (BVEL) calculation and equivalent circuit modeling (ECM). The BVEL calculation suggests that the Ag1 displacement subjects to a double-well potential that originates from the anisotropic coordination symmetry and low coordination number at Ag1 site. The relaxor ferroelectric behavior, observed at 200 K ≤ T ≤ 270 K, is sensitive to thermal history and is ascribed to the Ag1 hopping in double-well potential. The temperature dependence of the matrix capacitance (obtained by ECM) is very similar with that of b axis (obtained by in situ XRD) at 123 K