Ca₂LaTaO₆:Bi³⁺/Mn⁴⁺ Phosphors with High Brightness Far-Red Emitting and Luminescence Enhancement for Plant Growth LED Lights and Temperature Sensor

Herein, Bi3+/Mn4+ doped Ca2LaTaO6 phosphors with a double-perovskite structure were successfully synthesized with solid-state reaction at high temperature. The photoluminescence (PL) performances were investigated in detail. The blue radiation (similar to 465 nm) from the Bi3+ ion and the red radiation (similar to 686 nm) originating from the Mn4+ ion were obtained under 313 nm excitation. Especially, the pathway of energy transfer (Bi3+ -> Mn4+) contributes to enhance the red emission intensity (Mn4+: similar to 686 nm) in Ca2LaTaO6:Bi3+/Mn4+ system. The PL mechanism of Ca2LaTaO6:Bi3+/Mn4+ was analyzed through luminescence lifetimes and PL spectra. Moreover, the emitting bands of Ca2LaTaO6:Bi3+/Mn4+ were primarily matched with the absorbing bands of carotenoids and phytochrome P-FR on behalf of plant growth, so the phosphors were suitable for the design of a plant growth light under near-ultraviolet to blue excitation. At last, the optical temperature dependent performances of the Ca2LaTaO6:Bi3+/Mn4+ were analyzed with luminescence intensity ratio technology. The sample has presented excellent temperature measuring relative sensitivity (S-R = 2.106% K-1). The results illustrated that the Ca2LaTaO6:Bi3+/Mn4+ phosphor also can be used to develop an optical temperature sensor.