Electrical, dielectric, and optical properties of Sb2O3–Li2O–MoO3 glasses

Abstract

Temperature and frequency dependencies of DC and AC conductivities, dielectric response, static permittivity, optical absorption edge, infrared absorption spectrum, density, and temperatures of glass transition and crystallization for lithium molybdenum–antimonite glasses, (80−x)Sb2O3–20Li2O–xMoO3, where x=0–40, are measured and discussed. The DC conductivity increases with increasing concentration of MoO3. At 150°C, it ranges from 5×10−11S/m up to 3×10−8S/m. Polaron hopping between Mo5+ and Mo6+ ions contributes, probably, to the DC conductivity. Ionic conductivity by Li+ ions is also present. The conduction activation energy monotonously decreases from 1.15eV, at x=5, down to 0.91eV, at x=40. In all glasses with x>0, the conduction activation energy is close to a half of the indirect allowed optical gap. The pre-exponential factor, σ0, goes through a sharp maximum close to the composition (x=20) with both the highest glass transition temperature and the largest thermal stability range. The frequency dependence of the AC conductivity is composed of three components — the DC conductivity and two AC components. For x=35 and 40, the activation energy of electrical relaxation is equal to 0.954±0.008eV and the pre-exponential factor of relaxation times is equal to (4±1)10−14s. The static relative permittivity ranges from 17.4 to 23.0. Strong extrinsic absorption bands in infrared region originate from hydroxyl ions, CO2 impurities, and silicon–oxygen vibrations. The UV–visible indirect allowed absorption edge shifts from 2.6eV to 2.1eV with increasing MoO3 content. With increasing MoO3 content the glasses darken, from a light yellow color, at x=0, to a deep brown color, at x=40.