Study on the luminescence and structural properties of the novel Sr4Ca2W2O12 phosphors doped with Sm3+ for high color purity in white LED applications

A series of Sm3+ ions doped Sr4Ca2W2O12 phosphors was synthesized via the traditional solid-state reaction (SSR) method to investigate their potential for reddish-orange luminescence applications. This study introduces Sr4Ca2W2O12 as a promising host matrix with a monoclinic crystal structure (space group P1 21/c1), confirmed by powder X-ray diffraction (XRD) using JCPDS card no. 96-210-4689. The surface morphology and microstructure of the synthesized phosphor has been examined by recording the scanning electron microscopy (SEM) images for the titled phosphor. The Fourier transform infrared (FT-IR) spectroscopy confirmed the presence of characteristic functional groups. The optical band gap was estimated through diffuse reflectance spectroscopy (DRS), and Raman spectroscopy revealed active vibrational modes in 100-1000 cm(-1) range. Under 407 nm excitation, the phosphor exhibited strong red emission at 647 nm, corresponding to the 4G5/2 -> 6H9/2 transition of Sm3+ ions. The optimal doping concentration was determined to be x = 3.0 mol%, beyond which concentration quenching occurred. The optimized phosphor demonstrated CIE chromaticity coordinates of (0.606, 0.391), correlated color temperature (CCT) of 1625 K, and excellent color purity of 99.45 %, indicating its suitability for warm reddish-orange emission. Photoluminescence (PL) decay profiles showed bi-exponential behavior, and temperature-dependent PL (TDPL) studies confirmed excellent thermal stability, retaining 62.1 % emission intensity at 160 degrees C with an activation energy (Delta E) of 0.286 eV and relatively higher quantum efficiency (60.17 %). These properties suggests that Sr4Ca2W2O12:Sm3+ phosphor is a viable candidate for enhancing the red component in white light-emitting diodes (w-LEDs) and display technologies, addressing the challenge of poor red emission and low color purity (CP) in current phosphor-converted LEDs.