Influence of anionic substitutions on the nonlinear optical and luminescent properties of Ca9.75Eu0.5(VO4)7

Abstract

New anion-substituted vanadates, Ca_9.75±δEu_0.5(XO₄)_0.1(VO₄)_6.9 (X = As⁵⁺, S⁶⁺, Sb⁵⁺, Ta⁵⁺, Mo⁶⁺, and Te⁴⁺), are synthesized by a high-temperature solid-state method. Crystal structure, nonlinear optical properties, and photoluminescence excitation (PLE) and emission (PL) spectra are investigated. The maximum second harmonic generation (SHG) value is achieved for the compound containing Te⁴⁺, where the intensity increases by 6 times. For all samples, the most intense luminescence band is in the region of 613.5 nm at an excitation wavelength of 395 nm. The maximum and minimum luminescence are observed for Te⁴⁺ vanadate and Mo⁶⁺ vanadate, respectively. The presence of at least two bands in the region of the ⁵D₀ → ⁷F₀ transition indicates the low symmetry of Eu³⁺ polyhedra, which occupy at least two positions in the structure. The CIE color coordinates for all compositions except Ca_9.75Eu_0.5(VO₄)₇ are poorly distinguishable. Experimental data show that Ca_9.75±δEu_0.5(XO₄)_0.1(VO₄)_6.9 phosphors are promising candidates for solid-state-lighting applications.