Luminescence and energy transfer performances of Tb 3+ /Mn 4+ co-doped Sr 2 LuTaO 6 double-perovskite phosphors for a highly sensitive optical thermometer.

A series of Tb 3+ /Mn 4+ co-doped double-perovskite oxides Sr 2 LuTaO 6 (SLT) phosphors are synthesized by a solid-state method. The results of structural characterization prove that the Tb 3+ and Mn 4+ ions are successfully doped into the SLT host. The photoluminescence excitation (PLE) and photoluminescence (PL) spectra of Sr 2 LuTaO 6 :Tb 3+ , Sr 2 LuTaO 6 :Mn 4+ and Sr 2 LuTaO 6 :Tb 3+ /Mn 4+ are illustrated in detail. Under ultraviolet (UV) excitation, bright green and red lights are obtained from the Sr 2 LuTaO 6 :Tb 3+ /Mn 4+ phosphor. In particular, the emission intensity of Tb 3+ ions in Sr 2 LuTaO 6 :Tb 3+ /Mn 4+ is enhanced by the energy transfer (ET) process from Mn 4+ to Tb 3+ . The thermal enhancement of Tb 3+ ion radiation in Sr 2 LuTaO 6 :Tb 3+ /Mn 4+ also proves the ET process (Mn 4+ → Tb 3+ ). In addition, the thermal enhancement of Tb 3+ ion radiation and the thermal quenching of Mn 4+ ion radiation in the Sr 2 LuTaO 6 :Tb 3+ /Mn 4+ system can be applied to develop optical thermometry based on luminescence intensity ratio (LIR) technology. Therefore, the LIRs of Mn 4+ ( 2 E g → 4 A 2g ) and Tb 3+ ( 5 D 4 → 7 F 5,4 ) are investigated in the temperature range from 313 to 573 K. The absolute sensitivity ( S a ) and relative sensitivity ( S r ) of the Sr 2 LuTaO 6 :Tb 3+ /Mn 4+ phosphor are calculated. The maximum values of S a and S r are obtained from the LIR of Tb 3+ : 5 D 4 → 7 F 4 (570-599 nm) and Mn 4+ : 2 E g → 4 A 2g (625-705 nm). The maximum S a is 10.18% K -1 at 543 K, and the maximum value of S r reaches 1.98% K -1 at 543 K. These results confirm that the ET process from Mn 4+ to Tb 3+ contributes to increasing the temperature measuring sensitivity of the Sr 2 LuTaO 6 :Tb 3+ /Mn 4+ phosphor. Therefore, the Sr 2 LuTaO 6 :Mn 4+ /Tb 3+ phosphor has prospective potential in optical thermometry and provides advantageous guidance for designing high-sensitivity optical thermometers.