Synthesis of Magnesium Substituted Calcium Carbonate Phosphors Codoped with Cerium (III) and Terbium (III) and Its Fluorescence Property

Abstract

This study was made to investigate the synthesis and fluorescence property of magnesium substituted calcium carbonate phesphor codoped with Ce³⁺ and Tb³⁺ (calcite phosphor) in order to improve the emission intensity and stability of vaterite phosphor codoped with Ce³⁺ and Tb³⁺ presented in a previous paper. Magnesium substituted amorphous calcium carbonate phosphor codoped with Ce³⁺ and Tb³⁺ (amorphous calcium carbonate phosphor) was synthesized by adding 0.1 mol·dm^-3 (NH₄) ₂CO₃ solution into the mixed solution of 0.1 mol·dm^-3 MgCl₂ solution and 0.1 mol·dm^-3 CaCl₂ solution, which included TbCl₃ and CeCl₃ solution at 35°C. On the other hand, calcite phosphor was obtained by crystallizing amorphous calcium carbonate phosphor at 90°C for 1 hour in the mother liquor. The product was characterized by means of X-ray diffraction, thermal analysis and spectrophotometer.
The amorphous calcium carbonate phosphor and the calcite phosphor emitted green color by black light irradiation. The single phase of calcite phosphor was obtained below Mg/Ca atomic ratio of 0.42. The emission intensity of calcite phosphor was the maximum at this condition, and showed double the vaterite phosphor codoped with Ce³⁺ and Tb³⁺ that was synthesized in the previous paper. The increase of emission intensity was ascribable to a decrease of lattice strain and lattice constant by incorporating Mg²⁺ ion in the calcite structure. The emission intensity of calcite phosphor after thirty days decreased to half its initial value.