Cr3+-doped gallium-based transparent bulk glass ceramics for optical temperature sensing

A series of Cr3+-doped transparent bulk glass ceramics embedded with LiGa5O8, Ga2O3 or ZnGa2O4 nanocrystals were fabricated as the alternatives for Cr3+-doped single-crystals to explore their possible application in fluorescence lifetime based temperature sensing. X-ray diffraction, transmission electron microscopy and optical spectroscopy were adopted to investigate their microstructure and luminescent behaviors. Impressively, the decay lifetimes of these glass ceramic samples were found to be highly temperature-sensitive, attributing to the competition of radiation transitions from the thermally coupled Cr3+2E state with a long lifetime and 4T2 one with a short lifetime. Finally, such temperature-dependent luminescence of Cr3+ was successfully interpret by a two-level kinetic model, which gives a highest temperature sensitivity of 0.76% K−1 (at 295 K), 0.46% K−1 (at 370 K) and 0.58% K−1 (at 420 K) for the Cr3+-doped LiGa5O8, Ga2O3 and ZnGa2O4 glass ceramics, respectively.