Structure and Properties of a Novel Orange-Red Phosphor CaGdAlO4:Sm3+ for w-LEDs

Abstract A series of Sm3+-doped CaGdAlO4 (CGA) phosphors were successfully synthesized via a high-temperature solid-state method. The crystal structure and luminescent properties of the samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and fluorescence spectrometry, with Rietveld refinement confirming a tetragonal crystal structure (consistent with observed XRD patterns).The CGA:0.02Sm3+ phosphor can be efficiently excited by blue-violet light (408 nm), emitting intense orange-red luminescence. The optimal Sm3+ doping concentration is 2 mol % (maximum luminous intensity), and the concentration quenching mechanism is attributed to dipole-dipole interactions. The optimal sample exhibits excellent thermal stability in the range of 298–523 K, with an activation energy of 0.11 eV. When used as a red component in white LED (w-LED) devices, CGA:0.02Sm3+ delivers outstanding performance: a high color rendering index (Ra = 91.2) and CIE chromaticity coordinates of (0.3148, 0.3488), indicating its potential as an orange-red phosphor for lighting and display applications. Additionally, first-principles calculations based on density-functional theory (DFT) were performed to investigate the electronic structures and density of states of pure CGA and Sm3+-doped CGA.