Enlarging Sensitivity of Fluorescence Intensity Ratio-Type Thermometers by the Interruption of the Energy Transfer from a Sensitizer to an Activator

The occurrence of energy transfer (ET) would enhance the luminescence of the activator but sacrifice that of the sensitizer. However, the novel Sm3+-doped Ca2TbSn2Al3O12 (CTSAO) phosphor reported here seems to be an exception. In the series of CTSAO:xSm3+ phosphors investigated, something unexpected occurs; the activator, Sm3+, did not gain any energy compensation from the sensitizer, Tb3+, when temperature increases. Instead, when the loss of Sm3+ luminescence accelerates, simultaneously, the loss of Tb3+ luminescence accordingly alleviates. By careful calculations on the ET efficiency of the CTSAO:0.06Sm3+ phosphor at different temperatures, it is surprisingly found that the efficiency keeps decreasing as temperature increases. It means that the Tb3+-Sm3+ energy transfer is capable of being interrupted by an increasing temperature. By simulation, it is found that the occurrence of thermal interruption of energy transfer benefits the achievement of a higher temperature sensing sensitivity. In this sense, making use of the thermal interruption of energy transfer could become a novel route for further design of the fluorescence intensity ratio-type luminescence thermometers.