NOVEL THERMALLY-STABLE SR4ZN2W2O12: SM3+ PHOSPHORS SYNTHESIS, OPTICAL PROPERTIES AND APPLICATIONS IN WLEDS

Abstract

A series of reddish-orange emitting Sm3+ doped phosphors based strontium zinc tungstate Sr4Zn2W2O12:xSm3+(x=3, 5, 7 and 9 mol%) host were successfully synthesised via solid state reaction route. XRD analysis confirmed synthesis of highly crystalline lattice, indicating that dopant ions were successfully integrated into tungstate host lattice matching with standard JCPDS card no.96-156-3084. Scanning electron microscopy along with Fourier transform infrared spectroscopy characterizations provide insights into the micro structural irregular polyhedron morphology and used for identifying chemical bonds respectively. The optical band gap of Sr4Zn2W2O12 phosphors at optimize concentration x=7mol% was identified to be Eg=3.71 eV through diffuse reflectance spectroscopy (DRS). Optical investigation via photoluminescence (PL) studies a prominent excitation peak at 406 nm, under this excitation the phosphor exhibits a highly pure reddish-orange radiation recorded at 645 nm showing 4G5/2→6H9/2 energy transfer. At an optimal doping level, x=7 mol% concentration quenching phenomenon identified. The optimized phosphor showed CIE chromaticity coordinates (0.596, 0.401) along with outstanding colour purity of 99.99% and correlated color temperature (CCT) of 1625K thus making it suitable for reddish-orange emission This optimized material exhibited exceptional color purity of 99.99%, correlated color temperature (CCT) of 1625 K and CIE chromaticity coordinates (0.596, 0.401), making it appropriate for reddish-orange emission. Temperature-Dependent Photoluminescence (TDPL) results highlighted the materials robust thermal stability with retaining 76.43% emission intensity at 175oC, activation energy to be ∆E= 0.399 eV and quantum efficiency to be 76.9%. The results suggesting that Sr4Zn2W2O12:xSm3+ is a superior host for developing high performance w-LEDs.