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

V. Naresh,Nohyun Lee

Mn 4+ -activated KGaP 2 O 7 red emitting phosphor was successfully synthesized via traditional solid-state reaction method in air. The structural features of KGaP 2 O 7 : x Mn 4+ 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 GaO 6 polyhedra offer Mn 4+ ions to substitute the Ga 3+ sites in the crystal lattice resulting in a pure single phase structure with an efficient red emission at 702 nm (Mn 4+ : 2 E g → 4 A 2g ) under 452 nm excitation. The emission decay curves exhibited non-exponential nature with lifetimes shortening when Mn 4+ concentration is increased. Electric dipole-dipole interaction is identified to be responsible for the concentration quenching beyond 0.07 Mn 4+ via energy transfer between Mn 4+ ions. The temperature-dependent emission intensity for KGaP 2 O 7 :0.07Mn 4+ exhibited 66% at 423 K (150 °C) displaying good thermal stability and activation energy ( E a ) 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 Mn 4+ content (concentration quenching) and temperature (thermal quenching) on emission intensity are discussed based on the Tanabe-Sugano energy diagram and configurational coordinate scheme of Mn 4+ . Therefore, KGaP 2 O 7 :Mn 4+ phosphor can serve as a potential red emitting phosphor under blue light excitation and can also be useful to enhance plants growth.