Li 4 Zn(PO 4 ) 2 :Mn 2+ thermosensitive phosphor with dual luminescent centres for optical thermometry.

An optical thermometry strategy based on Mn 2+ -doped dual-wavelength emission phosphor has been reported. Samples with different doping content were synthesized through a high-temperature solid-phase method under an air atmosphere. The electronic structure of Li 4 Zn(PO 4 ) 2 was calculated using density functional theory, revealing it to be a direct band gap material with an energy gap of 4.708 eV. Moreover, the emitting bands of Mn 2+ at 530 and 640 nm can be simultaneously observed when using 417 nm as the exciting wavelength. This is due to the occupation of Mn 2+ at the Zn 2+ site and the interstitial site. Further analysis was conducted on the temperature-dependent emission characteristics of the sample in the range 293-483 K. Mn 2+ has different responses to temperature at different doping sites in Li 4 Zn(PO 4 ) 2 . Based on the calculations using the fluorescence intensity ratio technique, the maximum relative sensitivity at a temperature of 483 K was determined to be 1.69% K -1 , while the absolute sensitivity was found to be 0.12% K -1 . The results showed that the Li 4 Zn(PO 4 ) 2 :Mn 2+ phosphor has potential application in optical thermometry.