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 N-2 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 Omega 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.