Thermally stable double perovskite Ca₂YTaO₆: Tb³⁺, Eu³⁺ phosphor for warm white LEDs

A series of single-phase double perovskite Ca₂YTaO₆: Tb³⁺, Eu³⁺ phosphors were successfully synthesized by means of a high-temperature solid-state method. The crystal structure, luminescence spectrum, decay lifetime, thermal stability and energy transfer properties were investigated in detail. Under the excitation of 250 nm, Ca₂YTaO₆: Tb³⁺, Eu³⁺ had notable green and red light emissions at 551 nm and 618 nm, respectively. The optimal doping concentration of Tb³⁺ was 16 mol%. Owing to the energy transfer effect between Tb³⁺ and Eu³⁺, a tuneable luminescence from green to yellow was realized with the increase in Eu³⁺ doping concentration. When the temperature of the phosphor was increased from 300 to 500 K, the emission intensity remained 75% of that at room temperature. The Ca₂Y_0.82TaO₆: 0.16Tb³⁺, 0.02Eu³⁺ phosphor was encapsulated with a 365 nm chip, and a warm white LED with CIE colour coordinates (0.365, 0.371) and low colour temperature (CCT < 5000 K) was successfully prepared.