Dual-mode optical thermometer based on fluorescence intensity ratio of Eu³⁺/Mn⁴⁺ co-doping zinc titanate phosphors

Zinc titanate phosphors containing Eu³⁺/ Mn⁴⁺ as active ions were synthesized by using the solid-state method. XRD patterns of the powders confirmed that the samples were a mixture of cubic Zn₂TiO₄ and hexagonal ZnTiO₃ phases. The luminous intensity of ZTO: Eu³⁺phosphors and ZTO: Mn⁴⁺ phosphors both increased with the increase of doping concentration, reaching the maximum at 2 mol% Eu³⁺ and 0.3 mol% Mn⁴⁺, respectively. In the photoluminescence spectra of ZTO: Eu³⁺(2 mol%) phosphors with different Mn⁴⁺ doping amounts excited at 465 nm, the emission spectra revealed the characteristic peaks of Eu³⁺ with low Mn⁴⁺ content, and with the Mn⁴⁺ content increasing, the emission spectra contained both Mn⁴⁺ and Eu³⁺ luminescence peaks. In the variable temperature spectra, the relative sensitivity of the samples was improved with the concentration of Mn⁴⁺ increasing and achieved the maximum value of 3.2 %/K.