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 K2La1.0Eu1.0Ti3O10 offers more excellent performance in quantum efficiency, thermal stability and conductivity than those of Na2La1.0Eu1.0Ti3O10, which shows their potential applications in LEDs and FEDs as a suitable red-emitting phosphor.