Upconversion luminescence and optical temperature sensing of Er3+-doped La2Mo2O9 phosphors under 980 and 1550 nm excitation

A series of Er3+-doped La2Mo2O9 phosphors are prepared by the solid-state method. Up-conversion luminescence properties of La2Mo2O9:Er3+ are studied in detail under 980 and 1550 nm excitation. By inspecting the power dependent up-conversion intensity, indicating the two- and three-photon up-conversion population processes for 980 and 1550 nm excitation, respectively. The thermally coupled energy levels of 2H11/2 and 4S3/2 exhibit strong temperature dependence in the range of 293–533 K. Based on fluorescence intensity ratio technology, the La2Mo2O9:Er3+ phosphors present the maximum absolute sensitivity of 78.95 × 10−4 K−1 at 493 K and high relative sensitivity of 1.16% K−1 at 293 K under relatively safe wavelength of 1550 nm excitation. The results suggest that La2Mo2O9:Er3+ phosphor can be used as excellent optical temperature sensor.