Nd 3+ :Er 3+ :Yb 3+ codoped Al 2 O 3 powder is prepared by the nonaqueous sol-gel method and pressed into a small wafer. The two-stage sensitization processes for energy transfer among Yb 3+ , Er 3+ , and Nd 3+ are discussed. Under a 978-nm semiconductor laser excitation, the photoluminescence intensities at 813 and 887 nm, corresponding to the 4 F 5/2 + 2 H 9/2 → 4 I 9/2 and 4 F 3/2 → 4 I 9/2 transitions of Nd 3+ ions, enhance monotonously with the increasing temperature, and the fluorescence intensity ratio of the near-IR emissions can be fitted the exponential function R=3.12 exp(-1150/T) in the temperature range of 375 to 889 K. The maximum sensitivity is 0.0015 K -1 at 574.3 K. The data are of undoubted repeatability, and the material is applicable for sensitive, high-temperature measurement.