Short-range order changes induced by heat treatment in yttrium–aluminosilicate glasses

Abstract

Short-range order and local atomic configuration in yttrium–aluminosilicate glasses doped with gadolinium were studied by infrared (IR) spectroscopy, 27Al magic-angle-spinning nuclear magnetic resonance (MAS-NMR) and Gd 3+ electron spin resonance (EPR) on as-prepared and heat-treated samples. A small amount of yttrium was replaced by gadolinium in the host glass because Y 3+ and Gd 3+ cations are quite similar and gadolinium ions can be used as structural sensor in electron paramagnetic resonance measurements. The results evidence weak changes in the structure of as-prepared glasses with respect to the coordination of aluminium atoms produced by gadolinium doping (0.2 and 0.5 mol%). New IR bands recorded from heat-treated samples are associated with stretching modes of hexacoordinated aluminium in AlO 6 octahedra. The effect of the heat treatment on aluminium environment is estimated by analysing the relative intensity of the component lines of simulated 27Al MAS-NMR spectra. High-coordinated AlO n species were identified in all samples. EPR results evidence the increase of the number of gadolinium sites with weak crystal field as effect of the structural relaxation.