Luminescent properties of chromium(III)-doped lithium aluminate for temperature sensing

A series of novel temperature-sensitive phosphors LiAl _5(1-x)O₈: xCr³⁺ (x = 0.001-0.012) are synthesized by combustion method. The phosphors can be efficiently excited by the whole wavelength range of the visible light, producing strong deepred emission, which can be assigned to the ²E → ⁴A ₂ transition. The intensity, peak wavelength and decay lifetime of the emission are measured to vary strongly with temperature for all the samples. Especially, the decay lifetime change dramatically from 4.31 ms to 0.38 ms from 200 K to 600 K for the sample with x = 0.002, which give a highest temperature sensitivity of -0.015 ms K^-1 at 400 K and a maximal relative sensitivity of 0.83% K^-1 at 447 K. These results show that LiAl ₅O₈:Cr³⁺ is promising for optical thermometry.