Luminescence properties of the layered niobate KCa2Nb3O10 doped with Eu3+ and La3+ ions

The short-range structure of K2O-9TeO2 and K2O-4TeO2 in amorphous states such as glass and melt has been investigated by X-ray diffraction (XRD) and semi-empirical molecular orbital calculation (AM1-MOPAC method). The structure of amorphous alkali tellurites consisted of the TeO4 trigonal bipyramids (tbp) and the TeO3 trigonal pyramids (tp). Confirmed in the present work is that the TeO4 trigonal bipyramids characteristics of TeO2-based glasses transform into TeO3 trigonal pyramids with increasing modifier K2O content and a rise of temperature. The usage of XRD and MOPAC enabled us to comprehend in some details what to happen in phase transition from glasses to melts.