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

Abstract 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 (Ē) and 2E (2Ā) 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.