Mechanical and tribological properties of CdO + SnO2 thin films prepared by sol–gel

We report the mechanical and tribological properties of transparent conductive oxide CdO+SnO2 coatings. The films were deposited on glass substrates by the sol-gel technique using, as precursor solution, a mixture of CdO and SnO2 solutions obtained at room temperature. Depending on the Sn atomic concentration percentage values the X-ray diffraction patterns show three types of films constituted of i) CdO + Cd2SnO4, ii) Cd2SnO4 and iii) Cd2SnO4+ CdSnO3 crystals. Reciprocal microfriction tests revealed that films with Cd2SnO4 phase have friction values in the range 0.48 to 0.51 and a low wear rate of ~5×10 mmNm. Nanoindentation tests have shown an increment of the elastic modulus from 50 GPa for CdO + Cd2SnO4 films to 90 GPa for Cd2SnO4 films, while the hardest coating was the one constituted by Cd2SnO4 crystals with H=5.7 GPa, comparable to the hardness and elastic modulus reported for ITO films.