Effective attainment of a substantial proportion of the PbTiO3 crystalline phase through a non-isothermal crystallization process

Abstract

The crystallization kinetics studies were performed on a lead–titanium borate glass with a composition 50PbO–25TiO2–25B2O3 (mol %) to well understand the crystallization process by a non-isothermal method in an attempt to obtain a substantial proportion of the lead titanate (PbTiO3) crystalline phase. Based on the DTA result, the glassy material was heat-treated to induce crystallization and then produced a glass-ceramic. The broad hump observed in the XRD patterns of a glassy sample affirmed its amorphous nature. However, XRD studies conducted on a glass-ceramic revealed the evolution of the crystalline phase of PbTiO3 and a minor phase of TiO2. The phase relationship of PbTiO3 resulting from the reaction between PbO and TiO2 during a non-isothermal crystallization process has been examined. The activation energy for the crystallization of PbTiO3 is evaluated to be 135 kJ/mol (at PbO/TiO2 ratio = 2/1 mol %). When the Pb/Ti ratio exceeds 1, the process progresses nearly to completion by the first crystallization peak, and the PbTiO3 phase formation is easier. The fraction of PbTiO3 phase in the present glass is 98.3 % at PbO/TiO2 ratio = 2/1 mol %. In addition, FTIR spectra provided the presence of Ti4+ ions in the glass-ceramic. According to the values of crystal growth and Avrami index, surface crystallization and one-dimensional growth mechanisms are suitable mechanisms for contributing to the crystallization of this glassy sample. The obtained findings provided details on the crystallization behaviour of this glassy sample and excellent insight into obtaining the PbTiO3 crystalline phase in a large proportion, which is of great importance in future technological applications.