The effects of CeO2 addition on crystallization behavior and pore size in microporous calcium titanium phosphate glass ceramics

In this research the effect of the addition of CeO2 to microporous Calcium Titanium Phosphate glass ceramics was studied. Different molar percentages of CeO2 were added to three samples of a base glass whose composition was P2O5 30, CaO 45, TiO2 25 (mol%). The first sample had 2 mol% CeO2, the second sample had 4 mol% CeO2, and the third sample had 6 mol% CeO2. The fourth sample did not contain any CeO2. The glass samples were melted and crystallized to bulk glass ceramics by a conventional method. Differential Thermal Analysis (DTA) was utilized to determine the appropriate nucleation and crystallization temperatures. Among the samples, the DTA curve of the sample which had 2 mol% CeO2 had the sharpest crystallization peak. Therefore, this sample was chosen to prepare the glass ceramics. Using X-ray Diffraction (XRD) it was found that in all samples β-Ca3(PO4)2 and CaTi4(PO4)6 were the major phases. The β-Ca3(PO4)2 phase was dissolved away by soaking the glass ceramics in HCl, leaving a porous skeleton of CaTi4(PO4)6. CeO2 addition increased the glass transition temperature and decreased the crystallization time and temperature. It was shown that CeO2 addition resulted in an increase in the mean pore diameter while the specific surface area decreased. The median pore diameter and specific surface area were determined as 27 nm and 14 m2/g, respectively, for the sample containing 2 mol% CeO2.

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► We prepare a phosphate glass ceramic in the system of CaO–TiO2–P2O5 and add 2 to 6 mol% CeO2 to it. We determine the optimum percentage of CeO2 addition.
► We study phase separation, suitable time and temperature for crystallization in the microporous Calcium Titanium Phosphate Glass Ceramics utilizing DTA, SEM and XRD.
► We investigate on pore size utilizing BET and SEM techniques before and after CeO2 addition.
► CeO2 increases the pore size in the Calcium Titanium Phosphate Glass Ceramics.