The tribological properties of YBa2Cu3O7 films in ambient environment

In the present study, high-Tc superconducting thin YBa2Cu3O7 films and polysilicon films were prepared to investigate the initial sliding friction properties using a ball-on-flat tribometer when samples were moved against a sapphire ball or a steel ball in ambient environment. The surface topography was measured with atomic force microscope (AFM). After five times testing, the experimental results indicate that the friction coefficient of YBa2Cu3O7 films is lower than that of polysilicon films when sliding against a sapphire ball and almost the same when sliding against a steel ball. In particular, the initial friction of YBa2Cu3O7 films is more stable when sliding against a sapphire ball. However, the initial friction of polysilicon films fluctuates during a cycle period when sliding against a sapphire ball. They are both stable when sliding against a steel ball. Although, the surface profile of the YBa2Cu3O7 film is rough and can be seen to be rougher than the polysilicon film, but the friction coefficient of the YBa2Cu3O7 film is lower than that of polysilicon film. Also, although the topography of YBa2Cu3O7 films changes during friction, the friction coefficients are stable. This clearly shows that the initial sliding friction of YBa2Cu3O7 films under microfriction is stable. The observation signifies YBCO film is a good film to prevent stick–slip motion in ambient environment. The wear properties of YBa2Cu3O7 films suggest that the superconducting outgrowths (CuO) are loose and they can be easily removed.