Synthesis and spectroscopic analysis in Ca3NbGa3Si2O14: Ln3+(Ln= Sm,Tb) phosphor for optical applications

Abstract

The orange red emitting Ca₃NbGa₃Si₂O₁₄: Sm³⁺, Tb³⁺ phosphor was synthesized by solid-state reaction (SSR) method at 1280 °C for 10 h followed by annealing at 400 °C for 7hrs. X-ray diffraction pattern confirms the hexagonal structure with P321(No.150) space group. Compound formation, elemental analysis, photoluminescence and energy transfer mechanism from Tb³⁺ to Sm³⁺ were studied. Ca₃NbGa₃Si₂O₁₄:Sm³⁺ phosphor exhibits orange-red emission at 601 nm attributed to ⁴G_5/2$\to$⁶H_7/2 transition. Ca₃NbGa₃Si₂O₁₄:Tb³⁺ phosphor exhibits green emission at 544 nm attributed to ⁵D₄ $\to$ ⁷F₅ transition. The optimum concentration for Sm³⁺ and Tb³⁺ is found to be 3.0 and 2.0 mol. % respectively. Lifetime decay measurements of Tb³⁺ confirms the energy transfer mechanism which was proved to be a quadrupole-quadrupole interaction. The CIE chromaticity coordinates calculated for Sm³⁺ (0.63, 0.37), Tb³⁺ (0.27, 0.72) and 2.0 Tb³⁺, ySm³⁺ (0.37, 0.40) suggests its potential use for fabrication of optical devices. Higher values of Ω₄ indicate centro-symmetric character of the field experienced by Sm³⁺ ions. This confirms that magnetic dipole transitions are dominant over electric dipole transitions which are analogous to the PL results. Since the obtained values of the branching ratios with respect to transition, ⁴G_5/2 $\to$ ⁶H_7/2 are around 50 %, this material can be proposed as a potential laser material having emission wavelength around 601 nm.