Red-light-emitting inorganic La2CaZnO5 frameworks with high photoluminescence quantum efficiency: Theoretical approach

A series of Eu3+ doped CaLa2ZnO5 (CLZ) phosphors varying the Eu3+ concentration have been synthesized by the combustion route. The crystal structure, luminescent properties, thermal stability, quantum efficiency and the use of the phosphor in the phosphor-converted light emitting diodes (LEDs) were investigated in detail. The X-ray diffraction results confirmed the formation of a single-phase CLZ with a tetragonal symmetry. The crystal structure was refined via the Rietveld method, and it was observed that the crystal structure was composed of three different interlinked polyhedra LaO8, CaO10 and ZnO4, which makes the structure very stable. The CLZ:Eu3+ phosphors irradiated with ultraviolet and blue light exhibited the characteristic red photoluminescence (PL) emissions owing to the D-5(0) -> F-7(J) transitions. The optimized CLZ:5% Eu3+ phosphor showed an excellent thermal stability of 90% up to 498 K. The internal quantum efficiency of the optimized CLZ:5% Eu3+ was found to be 55.48% under the blue excitation of 467 nm. The excellent color purity of 91%, luminescence efficiency and stability with CIE coordinates at the pure red end (x=0.64, y=0.34) makes CLZ:Eu3+ phosphor an efficient red emitting candidate for UV and blue LED chips. (C) 2015 Elsevier Ltd. All rights reserved.