Sensitive temperature reading from intensity ratio of Cr3+ and defects’ emissions in MgTiO3:Cr3+

The luminescence thermometry based on the intensity ratio of Cr3+ and host emissions in the Cr3+ activated MgTiO3 phosphor powder is demonstrated over the 100–350 K temperature range. Phosphor was prepared by a two-step procedure based on the sol-gel and molten salt methods. Rhombohedral crystal structure of the material is confirmed by X-ray diffraction analysis, and the mean crystallite size of the powder was calculated to be ~ 32 nm. Morphology was investigated using scanning electron microscopy showing ellipsoidal, densely packed grains with 100 nm–150 nm average size. Photoluminescence emission spectra recorded under 385 nm excitation showed the broad host emission centered at ~ 485 nm and the Cr3+ emission around ~ 700 nm. The temperature-dependent emission spectra showed that host-emission intensity is almost temperature invariant, while the intensity of the Cr3+ emission rapidly decreases from 200 K to 350 K. Such behavior theoretically modelled and further applied for the ratiometric luminescence temperature sensing showed the maximal relative sensitivity of ~ 2.6% K-1, temperature resolution of 0.3 K, and excellent repeatability.