Evolution of non-ohmic characteristics and luminescent properties in dual-functional Tb-doped ZnO-Bi2O3-based varistor ceramics

Tb 3+ ions were pre-introduced into ZnO to synthesize ZTb phosphors, which were subsequently compounded with MnO 2 -Co 2 O 3 -Sb 2 O 3 -SiO 2 - x Bi 2 O 3 (MCSS- x B) to prepare dual-functional varistor ceramics. The effects of Bi 2 O 3 content on the microstructural, nonlinear electrical, and photoluminescence properties of the ZTb-MCSS- x B varistor ceramics were systematically investigated. Results show that the presynthesized ZTb phosphors exhibit efficient host-sensitized nonradiative energy transfer from the ZnO matrix to Tb 3+ ions. Driven by lattice distortion and charge compensation, hybrid defect clusters form, producing, a broadband emission centered at 540 nm. Upon sintering with MCSS- x B, the microstructure and double Schottky barrier characteristics of the varistor ceramics are significantly modulated. At an optimal Bi 2 O 3 content of 0.9 mol%, the ceramic exhibits a dense microstructure with an average grain size of 3.26 μm, a maximum barrier height of 1.58 eV, a high nonlinear coefficient of 70.2, and a low leakage current density of 8.95 μA/cm 2 . Importantly, the continuous Bi-rich liquid phase relieves lattice strain and decouples Tb-defect clusters, resulting in energy reconfiguration from the broadband luminescence of the ZTb phosphor to transition-metal-activated sharp emissions, characterized by an intense red emission at 750 nm and a near-infrared emission at 828 nm originating from Mn 4+ ions and Mn 4+ - V O defect complexes, respectively. These findings demonstrate a feasible strategy for simultaneously achieving superior nonlinear electrical performance and multicenter photoluminescence in ZnO-Bi 2 O 3 -based varistors.