The tri‐emitting phosphate phosphors SrIn2(P2O7)2: Tm, Dy, Eu for ratiometric optical thermometer

Abstract Developing new phosphors used for ratiometric optical thermometers has attracted broad attention recently. According to the recent research, the phosphate SrIn 2 (P 2 O 7 ) 2 with regard to the structural rigidity has been adopted as the host of Tm and Dy activators behaving the super‐stable white emission. Herein, Tm, Dy, Eu tri‐doped phosphors were prepared to investigate the interaction of three different activators and their coupling sensitivity to temperature. Based on concentration control and energy transfer among three activators, the tunable emission, including the idea warm white, has been obtained. In the case of increasing temperature, the emission intensities of Dy 3+ and Eu 3+ partially decrease, whereas the Tm 3+ fluorescence extremely keeps increasing to 155.4% of 473 K compared with that of room temperature. This phenomenon can be defined the negative thermal‐quenching. It is believed that the back energy transfer (BET) from Dy 3+ and that from Eu 3+ to Tm 3+ help the negative thermal‐quenching of Tm 3+ to a certain extent. Both cation occupation and structural rigidity obviously affect the BET efficiency. In the new phosphors, the fluorescence intensity ratios of Tm 3+ and Eu 3+ (blue/red) and (blue/orange) of Tm 3+ /Dy 3+ are closely related to temperature and vary linearly over a wide temperature range, which can be regarded as an important index of temperature sensor. The SI 1.92 P: T 0.01 D 0.01 E 0.06 shows excellent temperature sensitivity and recyclability. The current results show that SrIn 2 (P 2 O 7 ) 2 : Tm, Dy, Eu phosphors can be regarded as candidate materials for optical thermometry.