Synthesis of Yb3+/Er3+co-doped Ca9Gd2W4O24 crystals for use in optical thermometry

Ca9Gd2W4O24: Yb3+/Er3+ crystals were synthesized by solid state method. The structure, morphology, size and upconversion luminescence features had been characterized. These results indicated that Ca9Gd2W4O24 has a tetragonal cell and irregular blocky particle shapes. In upconversion, green (2H11/2, 4S3/2 -> 4I15/2) and red (4F9/2 -> 4I15/2) emissions were observed, both of which occurred via a two-photon populating process. Additionally, characteristics of the green UC emission were studied, including its temperature ranging from 298 K to 503 K and the sensitivity was 0.0075 K-1 at 473 K. This result indicated that Ca9Gd2W4O24: Yb3+/Er3+ crystals may have potential application in high temperature environment as safety sign.