Structural and optical characteristics of novel rare‐earth‐free red-emitting BaSn(PO4)2:Mn4+ phosphor

Abstract

Red phosphor is an indispensable component in the development of warm white light-emitting diodes (w-LEDs). However, most of the current red phosphors suffer from shortages of high cost, complex synthesis process and harsh preparation conditions. In this paper, a phosphate-based red emitting phosphor without rare earth doping has been investigated. A series of xMn4+ ions (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10 mmol) doping BaSn(PO4)2 phosphors were prepared by solid-state reaction. According to the X-ray diffraction (XRD) data, the phosphor belongs to monoclinic structure (C12/m1). The XRD refinement results show that with the increase of Mn4+ ions doping concentration, the β angle in the cell parameters of BaSn(PO4)2:xMn4+ phosphor gradually decreases, which indicates that the crystal cell is distorted. The morphology, elemental composition and molecular structure of the phosphor were studied by SEM, XPS and FT-IR. The band gap of the BaSn(PO4)2 host obtained by diffuse reflectance spectroscopy is about 3.59 eV, and the band gap decreases gradually with the Mn4+ ions doping content. From the room temperature fluorescence spectra, it is found that the phosphor emits red light when the excitation wavelength is 468 nm, and concentration quenching occurs at the doping concentration of x = 0.06. When the temperature rises to 423 K, the emission intensity of the phosphor remains at 76.7% of the original intensity at room temperature, and the activation energy Ea is calculated to be 0.1261 eV, indicating that the phosphor has excellent thermal stability. These results indicate that BaSn(PO4)2:xMn4+ is an excellent red phosphor.