Multimode fluorescence intensity ratio thermometer based on synergistic luminescence from Eu3+ to Mn4+ of SrTiO3:Eu3+-ZnTiO3:Mn4+ nanocomposites

SrTiO3:Eu3+-ZnTiO3:Mn4+ nanocomposites were successfully synthesized to obtain highly sensitive optical thermometers. The synthesized SrTiO3:Eu3+ was cubic perovskite structure, and the synthesized ZnTiO3:Mn4+ was cubic perovskite structure accompanying with hexagonal ilmenite structure. The results of X-ray diffraction and Fourier transform infrared spectra suggested that the mixture of SrTiO3:Eu3+-ZnTiO3:Mn4+ nanophosphors had no obvious change in the structure after heat treatment at 800 °C. The photoluminescence intensity of Eu3+ in SrTiO3 phosphors revealed a stable temperature dependence, while that of Mn4+ in ZnTiO3 phosphors revealed a sharp temperature dependence. The emission band ranging from 650 nm to 800 nm were separated into two bands centered at 690 nm and 714 nm, which were assigned to 4T2g→4A2g and 2Eg→4A2g transitions of Mn4+ ions in cubic perovskite and hexagonal ilmenite ZnTiO3 matrix, respectively. The maximum relative sensitivity revealed a dependence on the molar ratio between SrTiO3 and ZnTiO3. The maximum value of 3.3 %K−1 was achieved for the composites with the molar ratio of 1:3 between SrTiO3:Eu3+ and ZnTiO3:Mn4+ nanophosphors, which was higher than that of the composites before heat treatment, 3.1 %K−1. The results suggested the potential application in optical temperature probes for the composites.