Caracterização estrutural e estudo do efeito de íons mistos no sistema K-Li metafosfato

Abstract

The phosphate glasses have awakened the interest of researchers due to its interesting properties, such as: low melting point, high ionic conductivity, good optical transparency, high expansion coefficient, better ability in dissolving big amounts of alkaline oxide metals and high potential in technological applications like sensors, solid state batteries, industrial waste immobilizers, etc. Different formulations of alkaline vitreous systems have been developed to be used in solid electrolytes batteries, due to its ionic conductivity. Nevertheless, the mixture of two different ions in the same vitreous matrix can cause an effect known as mixed ion effect (MIE). This effect provokes non-linear variations in many physical properties, specially in the ionic conductivity, leading a minimum to heat up as the concentration of ions in the vitreous net varies. The main objective of this paper was the preparation of phosphates glasses in the system K x Li(1-x)PO3 , in which 0 ≤ x ≤ 1, and to study the MIE in some properties such as: vitreous transition temperature, density and ionic conductivity. The amorphous structure has been verified by X-ray diffraction (XRD), and the structural characterization has been done through the techniques Ramman spectroscopy and Nuclear Magnetic Resonance (NMR). The study of physical properties of glasses has been done by the techniques Differential Scanning Calorimetry (DSC), Density by the Archimedes method and Impedance Spectroscopy. Analysis of DSC show that vitreous transition (Tg) exhibit a weak MIE. The ionic conductivity presents an intense MIE in which it is possible to verify a variation of approximately seven orders of magnitude compared to the linear behavior in room temperature. This study establishes that the mixed ion effect can be explained as a natural consequence of the random mixture of ions, validating the model of the random distribution of ions in the study of another vitreous system not yet found in literature.