High-temperature structure of K 2O–TeO 2 glasses

Abstract

The structural change of K 2O–TeO 2 glasses ( xK 2O:TeO 4, x:5, 10, 15, 20, 25 and 30 mol%) from room temperature to a temperature higher than the melting point ( T m) was studied by the use of Raman spectroscopy, XRD (X-ray diffraction), X-ray RDF (radial distribution function) and XAFS (X-ray absorption fine structure) spectroscopy. The Raman results indicated that TeO 4 trigonal bipyramid (tbp) units convert to TeO 3 trigonal pyramid (tp) units with increasing temperature and by the addition of K 2O to the K 2O–TeO 2 glasses. We found that a 10K 2O · 90TeO 2 (mol%) glass mainly consists of TeO 4 tbp unit, while 20K 2O · 80TeO 2 (mol%) and 30K 2O · 70TeO 2 (mol%) glasses are composed of the mixture of TeO 4 tbp and TeO 3 tp units. The high-temperature XRD and X-ray RDF results are in agreement with the results of high-temperature Raman spectroscopy. Furthermore, the XAFS spectroscopy shows that potassium ions have a similar local structure in all of the K 2O–TeO 2 glasses studied.