Fluorescence properties of Sr_x(La_9.2−xTb_0.8)(SiO₄)₆O_α (x = 2–6) prepared by heat-treating mixtures of SrCO₃, La₂O₃, SiO₂, and Tb₄O₇

Abstract

In this study, phosphors based on Sr_x(La_9.2−xTb_0.8)(SiO₄)₆O_α (x = 2, 3, 4, 5, and 6) ceramic powders were prepared and their photoluminescence (PL) spectra were investigated. The phosphors show green emission at approximately 545 nm when excited by 378 nm UV light. X-ray photoelectron spectroscopy suggests that Tb in the Tb³⁺ and Tb⁴⁺ valence states coexist in phosphors at a Tb³⁺/Tb⁴⁺ atomic ratio of unity. [Sr_2−x(La,Tb)_x]SiO_α was confirmed to exist in addition to Sr_x(La_9.2−xTb_0.8)(SiO₄)₆O_α at x = 4, 5, and 6. The PL intensity increased with increasing Sr(x) content, which is considered to be due increasing Sr_x(La_9.2−xTb_0.8)(SiO₄)₆O_α particle size. The strongest PL intensity was observed at x = 6, where the absorptivity, internal quantum efficiency, and external quantum efficiency were 20, 50, and 10 %, respectively.