Structural and low temperature electrical transport properties of Mo-doped vanadium oxide NTC ceramic thin films

Abstract

Mo doped V2O3 [V1−xMoxO2−x/2 (x = 0, 0.5–1)] ceramic thin films were prepared on metal substrates by sol-gel dip coating and the influence of Mo addition on their microstructure, negative temperature coefficient (NTC) electrical transport properties and metal to insulator phase transition behavior were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), and resistance-temperature measurements. Resistivity-temperature curves (over a temperature range of 273.15–253.15 K) indicated that all of the prepared thin films have NTC effects, after annealing with 20 sccm N2 at 673.15 K. It was demonstrated through microstructure analysis at Mo high concentration, (i.e., x > 0.07) it segregates at the V2O3 grain boundaries, causing scattering and distortion of the crystal lattice. Compared with the other V2O3 films, the films prepared at Mo x > 0.07 offered the high resistivity and moderate thermal constant (B) values. In particular, V2O3 doped with 10 mol % Mo showed excellent NTC properties and high resistivity (0.072 Ω cm). At sub-zero temperatures, the variation of electrical transport properties of the V2O3 films is correlated with Mo concentration, micro-structure and Joule effect.