A double perovskite Ca₂MgWO₆:Bi³⁺ yellow-emitting phosphor: Synthesis and luminescence properties

Novel double perovskite Ca₂MgWO₆:Bi³⁺ (CMW:Bi³⁺) yellow-emitting phosphor is synthesized by solid-state reaction method in air. Host Ca₂MgWO₆ with excitation 297 nm emits blue light and the chromaticity coordinate is (0.169, 0.160). The spectroscopic properties of CMW:Bi³⁺ phosphor are explained on the basis of the Bi³⁺ (6s²)–W⁶⁺ (5d⁰) metal-to-metal charge transfer (MMCT) transition. CMW:Bi³⁺ phosphor with excitation 338 nm shows yellow light and the chromaticity coordinate is (0.383, 0.477). Broad emission band peaking at ~550 nm of CMW:Bi³⁺ phosphor is observed in the range of 400–780 nm due to the D → ¹S₀ radiative decay and the ³P_1,0 → ¹S₀ transitions of Bi³⁺ ion. Monitored at 550 nm, excitation spectrum of CMW:Bi³⁺ phosphor including a strong excitation peak at ~338 nm covers the region from 200 to 400 nm owing to the Bi³⁺ → W⁶⁺ MMCT transition and the ¹S₀ → ³P₁ transition of Bi³⁺ ion. The optimal Bi³⁺ ion actual content is ~0.38 mol%. Emission spectra of CMW:Bi³⁺ phosphor with excitation 338 nm shows blue-shift with increasing temperature from 50 to 300 K owing to the influence of temperature to electron transfer. The possible luminous mechanism of CMW:Bi³⁺ phosphor is analyzed by energy level diagram of Bi³⁺ ion in solid including d⁰ cation.