Luminescence properties of near-UV excitable yellow-orange light emitting warm CaSrAl2SiO7:Sm3+ phosphors

Abstract

Single-phase CaSrAl2SiO7:Sm3+ phosphors were synthesized by traditional high temperature solid state reaction method. Formation of samples and phase analysis were confirmed by X-ray diffraction technique. Morphology was done by field emission scanning electron microscopy and elemental compositions were confirmed by energy dispersive X-ray analysis. Present phosphors have tetragonal crystallography with space group P4¯21m. Average crystallite size was calculated by using Scherrer and Williamson-Hall method. Photoluminescence study of CaSrAl2SiO7:Sm3+ phosphor was investigated. Under different excitation wavelengths, PL spectra consist of four emission bands at 564, 570, 601 and 650 nm. The emission bands located at 564 and 570 nm are associated with the transition 4G5/2 → 6H5/2 while emission bands at 601 and 650 nm are due to 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2, respectively. Intense emission was obtained when phosphor was excited under 404 nm wavelength. Non-radiative energy transfer process involved in concentration quenching, was also discussed. CIE coordinate is found in yellow-orange region, hence CaSrAl2SiO7:Sm3+ phosphors emit yellow-orange light when efficiently excited by near UV (∼400 nm) LED chip. Color purity and CCT of the phosphor were determined; CCT suggests that present phosphor is a good candidate as a warm yellow-orange color emitting phosphor. Effect of different heating rates and different UV exposure time on the TL glow curve of the phosphor was investigated. Activation energies and kinetic parameters for different traps were calculated by using peak shape method. TL emission spectrum was also recorded. Present article explains all the possible mechanisms associated with luminescence process in CaSrAl2SiO7:Sm3+ phosphors.