Structural, optical, elemental and photometric properties of Sm3+ activated Ca3Ga4O9 oxide phosphors for WLEDs

Abstract

Solid-state lighting systems rely on the exceptional characteristics of phosphor-converted LEDs, including long lifetime, low energy consumption, and high brightness. This study focuses on the synthesis of Sm3+ activated Ca3Ga4O9 (CGO: Sm3+) orange-red emitting oxide phosphors using the solid-state reaction method. X-ray photoelectron spectroscopy was used to analyze the nature of bonding with the dopant ion and oxidative states of the elements in the structure. Scanning electron microscopy and energy dispersive spectroscopy revealed agglomerated particles with a flake-like structure in the Sm3+ doped sample. The optical properties of the samples were investigated using UV-Visible diffuse reflectance and photoluminescence excitation and emission analyses. The Sm3+ doped samples showed maximum excitation at 404 nm and 479 nm, with corresponding energy level transitions of 6H5/2 - 6P3/2 and 6H5/2 - 4I11/2, respectively. Emission spectra exhibited four emission maxima at 564, 601, 645, and 708 nm, representing the 4G5/2 - 6H5/2, 4G5/2-6H7/2, 4G5/2-6H9/2, and 4G5/2-6H11/2 transitions of Sm3+ ions. The Kubelka-Munk function was used to calculate the optical energy gap values. Photometric parameters, including color coordinates, correlated color temperature, and color purity, were determined. The CIE chromaticity coordinates of CGO: Sm3+ were found in the orange-red region, indicating its potential as a promising candidate for use in phosphor-converted white LEDs applications. The study concludes that Sm3+ activated CGO phosphors have great potential for use in solid-state lighting systems.