Nd 2 O 3 film is a functional film with great potential application value. In this paper, thinNd 2 O 3 film was prepared on the surface of Si substrates using RF magnetron reactive sputtering. Nd 2 O 3 film with different crystal structures were controlled by changing the deposition temperature. The results show that the Nd 2 O 3 film with a cubic structure can be obtained at 150 °C, while a hexagonal structure appears at 250 °C and above. The refractive indices of the cubic and hexagonal Nd 2 O 3 films were 1.736 and 2.130, respectively. Moreover, the principle of the influence of deposition temperature on the refractive index of the film was illustrated. The hardness and the elastic modulus of the cubic Nd 2 O 3 film were 6.3 GPa and 102 GPa, respectively, which are much lower than the 9.9 GPa and 145 GPa of the hexagonal Nd 2 O 3 film. In addition, with a double-sided cubic Nd 2 O 3 film, the maximum transmittance of the diamond film reached 87.54%. The results show that the Nd 2 O 3 film is an anti-reflection film suitable for optical applications. • Nd 2 O 3 films with cubic and hexagonal structures were prepared, respectively. • The mechanical and optical properties of two kinds of Nd 2 O 3 films were compared. • Hexagonal Nd 2 O 3 film shows hardness of 9.9 GPa and elastic modulus of 145 GPa. • Diamond presents the maximum transmittance of 87.54% at 11.2 μm with Nd 2 O 3 films. [ABSTRACT FROM AUTHOR]