Crystallization behaviour of Li2O·Nb2O5·SiO2 glass containing TiO2

Abstract

This paper deals with the crystallization of glass 30Li2O?15Nb2O5?50SiO2?5TiO2 (mol%). The crystallization behavior was studied under isothermal and non-isothermal conditions. XRD and SEM methods were employed for determination of phase composition and microstructure of crystallized glass. It was detected that this glass crystallizes by the surface crystallization mechanism. SEM micrographs of the crystallized samples revealed that the crystals grow in the form of dendrites. The glass-ceramics with complex phase composition was obtained. Three crystalline phases were detected where LiNbO3 has grown as primary phase and a secondary ones Li2Si2O5 and SiO2 appeared. The calculated average crystallite sizes are: 27 nm for LiNbO3 , 115 nm for Li2Si2O5 and 45 nm for SiO2 . From the experimental data an activation energy of crystals growth, calculated using the Kissinger relation, is Ea = 275 ?10 KJ / mol.

The role of TiO2, ZrO2, BaO and SiO2 on the mechanical properties and crystallization behavior of fluorapatite–mullite glass–ceramics

“…A contradictory explanation can be recommended for the effect of barium and titanium oxides, i.e. they increase the numbers of non-bridging oxygen in the glasses and hereby decrease the viscosity of the glasses [18][19][20][21][22][23]. To investigate the crystallization procedure and development of the crystalline phases in the prepared glasses, the samples were heat treated at different temperatures for 3 h. Based on the XRD results, apatite and mullite were precipitated in the glasses after the mentioned heat treatment and there was not any footprint of other crystalline compounds, such as TiO 2 and ZrO 2 , in the XRD patterns, meaning that they did not act as a nucleation agent in the glasses.…”