DFT calculation, electric and luminescent property of titanate solid state electrolytes based red emitting phosphor A₂La₂Ti₃O₁₀:Eu³⁺ (A = Na, K)

Eu³⁺-activated red emitting phosphors based on the layered perovskite ion conductors A₂La₂Ti₃O₁₀:Eu³⁺ (A = Na, K) were successfully synthesized by a modified sol-gel method. Photoluminescence excitation (PLE), emission (PL) spectra and cathode-luminescence (CL) spectra were used to characterize the luminescent properties of samples A₂La₂Ti₃O₁₀:Eu³⁺ (A = Na, K). The band gap and electronic structure of A₂La₂Ti₃O₁₀ (A = Na, K) were analyzed by the density functional theory (DFT) calculation using the generalized gradient approximation (GGA). The temperature-dependent PL spectra were measured to investigate the thermal stabilities. Their conductivities have also been characterized by the measurements of alternating current (AC) impedance in the range of 200–500 °C over a frequency of 40 Hz–110 MHz, and the diffusional pathways of K and Na ions were also proposed using the bond valence maps (BVM). Results indicates that the phosphor K₂La_1.0Eu_1.0Ti₃O₁₀ offers more excellent performance in quantum efficiency, thermal stability and conductivity than those of Na₂La_1.0Eu_1.0Ti₃O₁₀, which shows their potential applications in LEDs and FEDs as a suitable red-emitting phosphor.