Temperature-dependent luminescent properties of Cr3+doped ZnGa2O4 far-red emitting phosphor

The far-red emitting phosphor plays a significant role in the agricultural lighting application. Herein, we present the temperature-dependent luminescent characteristic of Cr3+ doped ZnGa2O4 (ZGO) phosphor, which was synthesized using the conventional high temperature solid-state reaction. The prepared ZGO:Cr3+ sample was evidenced through the analyses of X-ray diffraction technique and X-ray photoelectron spectroscopy. Photoluminescence phenomena present an expected sharp R line origin from the spin forbidden transition of 2E -> 4A2 in Cr3+ ion. In the matrix of ZGO, the R line was divided into R1 and R2 lines as a result of the splitting of 2E level into 2E (E over bar ) and 2E (2A over bar ) levels at the distorted crystal field environment. Electron paramagnetic resonance spectrum of Cr3+ proved that g = 3.63 and 1.92 are attributed to the isolated Cr3+ ions and exchange coupled Cr3+-Cr3+ ion pairs. The red-shift of R1 and R2 lines were observed with the temperature rising from 140 K to 440 K. The Debye temperature estimated from the shift of R1 lines was 690 K. The luminescence decay curves of the ZGO:Cr3+ sample show long-lived lifetimes changing from 5.83 ms to 2.16 ms in the range of 140-440 K. Besides, the temperature sensing relative sensitivity increases with the elevation of temperature and reaches the maximum value of 0.582% K-1 at 400 K. The obtained results could promote the performance of Cr3+ doped phosphors for the applications in phosphor-converted light-emitting diodes and temperature sensing.