Glass formation, structure and ion transport in 0̇45Li 2O-(0̇55?x)P 2O 5-xB 2O 3 glasses

Abstract

The formation, atomic structure and transport properties of 0̇45Li 2O-(0̇55?x)P 2O 5-xB 2O 3 glasses are studied by keeping the molar ratio of Li 2O/(P 2O 5+B 2O 3) constant to focus on the cation mobility changes due to the mixed glass former effect. X-ray diffraction confirms glass formation of this system within the range of 0≤x≤0̇40. As the B 2O 3 content increases, the glass transition temperature (Tg) increases, molar volume decreases, and the glasses become more fragile. FT-IR, Raman and XPS spectroscopic studies indicate the formation of P-O-B bonds. Deconvolution of Raman and XPS spectra indicates a decrease of P-O-P, O-P-O stretching vibrations of phosphate chains, and an increase of P-O-B bonds with rising B 2O 3 content. The maximum fraction of P-O-B bonds was observed for x=0̇30. Nonbridging oxygens were found to reduce with increasing B 2O 3 content. The electrical conductivity of these glasses has been investigated over a temperature range from 300 to 479 K and the frequency range 150 Hz≤ω≤15 MHz by means of impedance spectroscopy. The highest ionic conductivity of 1̇02×10 ?7 S cm ?1 at room temperature with the lowest activation energy of 0̇63 eV was observed for x=0̇30. Analyses of impedance data, in the conductivity and modulus formalisms, as a function of temperature and frequency led to common super-master curves at all temperatures and all compositions indicating that the relaxation mechanism is a temperature independent universal process that essentially consists of a redistribution of the mobile Li + ions.