The influence of TiO2 on the structure and properties of sodium-zinc phosphate glasses

Abstract

xTiO2–(40-x)ZnO–10Na2O–50P2O5 glasses were prepared up to x = 20. The stabilizing effect of titanium on the phosphate glasses was tested. The structure of the glasses was studied by Raman, both 31P and 23Na MAS NMR spectroscopies and 31P static NMR. The increasing titanium content caused the change in the metaphosphate structure into pyrophosphate. The amount of reduced titanium was detected by electron paramagnetic resonance to be less than 0.5% and the coordination polyhedron of titanium was identified as the tetragonally distorted octahedron with some trigonal deformation. The results of basic thermoanalytical values, density and microhardness confirmed the anticipated influence of titanium on the strengthening of the glass network. The influence of titanium on surface layer thickness and solubility was tested in demineralized water and in a saline solution. It was determined that even a concentration of 1mol% TiO2 significantly decreases the degradation rate and thickness of the surface layer. The thickness of the surface layer of glass without titanium was found to be about 40 µm and the thickness of the surface layer of glass with 1 mol% TiO2 was found to be close to 7 µm. The results obtained correlate well with the significant stabilizing effect of titanium. It is possible to conclude that the determination of surface layer thickness does not depend on the solvent but only on the chemical composition.