A new double perovskite CaY0.5Ta0.5O3:Mn4+ deep-red phosphor: Synthesis, optical properties, and potential applications in plant-growth LEDs

Abstract Deep-red emitting CaY0.5Ta0.5O3:Mn4+ phosphors were obtained by optimizing the reaction temperature. The structure of CaY0.5Ta0.5O3:Mn4+ consisted of a double perovskite with the Pnma (62) space group. The luminescence intensity of the synthesized CaY0.5Ta0.5O3:0.3%Mn4+ at 1550 °C was twice as strong as that at 1500 °C. The photoluminescence spectra of the synthesized CaY0.5Ta0.5O3:Mn4+ phosphor exhibited a deep-red broadband luminescence from 650 nm to 750 nm with a 680 nm dominated peak due to the 2Eg→4A2g transition of Mn4+ in TaO6 octahedral structures. The optimal concentration for the CaY0.5Ta0.5O3:xMn4+ phosphor was 0.3 mol.%. The concentration quenching effect was ascribed to the dipole–quadrupole interaction. The decay time (0.398–0.171 ms) indicated that the forbidden character of 3d transitions existed among Mn4+. The crystal field strength and the Racah parameters were discussed to estimate the nephelauxetic effect of Mn4+ in the CaY0.5Ta0.5O3 host. Besides, the red light-emitting diodes (LEDs) were packaged using the CaY0.5Ta0.5O3:0.3%Mn4+ phosphor and a 368 nm near-ultraviolet chip. The emission spectrum of the red LED overlapped with the absorption curves of chlorophylls a and b. Results indicated that the CaY0.5Ta0.5O3:Mn4+ can serve as a component of the deep-red light in plant-growth LEDs.