Energy Transfer Studies on Red Emitting CaGdSbWO8: Sm3+/Eu3+ Phosphor for w-LEDs and Indoor Plant Growth Lighting System.

In the present research work, a solid-state reaction method was employed to synthesize a series of CaGd_(0.95-x)SbWO₈:Sm_0.05Eu_x (x = 1, 1.5, 2, 3 and 4 mol%) phosphors. The phase purity, crystallinity, morphological and compositional studies were analysed via X-ray diffraction (XRD), scanning electron microscopy (SEM) imaging, and energy dispersive spectroscopy (EDS) analysis. The Fourier transform infrared (FT-IR) spectroscopy was utilized to measure OH content in the prepared phosphor material. The diffused reflectance spectroscopy (DRS) analysis was applied to measure the optical energy band gap. The photoluminescence (PL) spectroscopy at excitation wavelengths 275 and 405 nm was carried out to analyze the luminescence properties of the prepared phosphors. The intensity of emission peaks of Sm³⁺ ions decreased as the concentration of Eu³⁺ ions increased showing the energy transfer mechanism from Sm³⁺ to Eu³⁺ ions. The dipole-dipole interaction mechanism is responsible for the energy transfer between Sm³⁺ to Eu³⁺ ions as assessed using the Reisfeld approximation. The CIE coordinates of the prepared samples lie in the warm red region represented by the relatively low (3200 K) value of correlated color temperature. These results show the suitability of the prepared phosphor for white light emitting diode (w-LEDs) and also in indoor plant growth lighting systems.