KGaP2O7:Mn4+ deep red emitting phosphor: Synthesis, structure, concentration and temperature dependent photoluminescence characteristics

Abstract

Mn4+-activated KGaP2O7 red emitting phosphor was successfully synthesized via traditional solid-state reaction method in air. The structural features of KGaP2O7:xMn4+ material were investigated by means of powder XRD & Raman, morphology from SEM, and element analysis, corresponding mapping through EDAX. In conjunction, concentration and temperature dependent spectroscopic properties were analyzed from UV–Vis reflectance, excitation, emission and lifetime decay curves. Powder XRD and photoluminescence profiles revealed that GaO6 polyhedra offer Mn4+ ions to substitute the Ga3+ sites in the crystal lattice resulting in a pure single phase structure with an efficient red emission at 702 nm (Mn4+:2Eg→4A2g) under 452 nm excitation. The emission decay curves exhibited non-exponential nature with lifetimes shortening when Mn4+ concentration is increased. Electric dipole-dipole interaction is identified to be responsible for the concentration quenching beyond 0.07 Mn4+ via energy transfer between Mn4+ ions. The temperature-dependent emission intensity for KGaP2O7:0.07Mn4+ exhibited 66% at 423 K (150 °C) displaying good thermal stability and activation energy (Ea) of ∼0.186 eV. From UV–Vis reflectance spectra using Tanabe-Sugano diagram, crystal splitting factor (Dq), two Racah parameters (B & C), Dq/B, C/B and energy of states are calculated to evaluate nephelauxetic ratio (β). In addition, the effect of Mn4+ content (concentration quenching) and temperature (thermal quenching) on emission intensity are discussed based on the Tanabe-Sugano energy diagram and configurational coordinate scheme of Mn4+. Therefore, KGaP2O7:Mn4+ phosphor can serve as a potential red emitting phosphor under blue light excitation and can also be useful to enhance plants growth.