Preparation and investigation of Dy3+/Tm3+-doped NaGd(MoO4)2 with thermal stability and tunable white light emission for LED applications

Abstract

In this work, a series of Dy³⁺-doped, Tm³⁺-doped, and Dy³⁺/Tm³⁺ co-doped NaGd(MoO₄)₂ (NGM) phosphors were successfully prepared via a high-temperature solid-state method. The crystal structure, band structure, elemental composition, and photoluminescence (PL) properties were investigated in detail. These crystals showed a tetragonal structure with the space group I41/a (88), which endowed NGM with excellent chemical and thermal stability. The positions of the diffraction peaks of the doped samples were slightly righted shift, indicating that the Dy³⁺ and Tm³⁺ ions occupied the position of the Gd³⁺ ions. The photoluminescence results showed that bright white light emission could be achieved by adjusting the excitation wavelength or controlling the ratio of the Dy³⁺ and Tm³⁺ ions concentration. The obtained optimal chromaticity coordinate (0.3334, 0.3310) for the NGM: 0.06Dy³⁺, 0.12Tm³⁺ phosphor was very close to the standard white light (0.333, 0.333) coordinate under near-ultraviolet (364 nm) excitation. Additionally, the temperature-dependent spectra were also investigated, which indicated that this phosphor has excellent thermal stability under 423 K. In conclusion, Dy³⁺/Tm³⁺ co-doped NGM has potential for application in white LEDs.