Red-light-emitting inorganic CaLa₂ZnO₅ frameworks with high photoluminescence quantum efficiency: Theoretical approach

Highlights: • CaLa₂ZnO₅:Eu³⁺ has been synthesized by the combustion route. • The crystal structure was refined via the Rietveld method. • Quantum efficiency was found to be 55.48% under the blue excitation of 467 nm. • A phosphor converted LED was constructed with the optimized phosphor. • Solid-state lighting and display applications when coupled with UV or blue chips. 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 ⁵D₀ → ⁷F_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.