The order–disorder transition of Ti³⁺–Ti³⁺pairs in Ti₄O₇and (Ti_1–xV_x)₄O₇

Abstract

Abstract Studies of electrical resistivity, specific heat, magnetic susceptibility and structural data are reported for Ti4O7 and (Ti1–xVx)4O7 single crystals (0 0·35 at.%, the disordered phase is stabilized down to the lowest temperatures obtained. The ordered phase is described in terms of a crystallization of charges related to interatomic Coulomb repulsion; the intermediate phase may be considered as a Wigner glass involving a random potential due to the disordered charges. The excitations of the Ti3+–Ti3+ pairs may be viewed as bipolarons, responsible for the transport properties of the intermediate disordered phase. The stabilization of the disordered phase by small concentrations of V is attributed to the increase of background disorder such as the forma...