Design criteria for stable friction drive operation of surface acoustic wave motor

Design criteria for the stable and durable operation of a surface acoustic wave motor were discussed. The low electric conductivity coupled with pyroelectricity of lithium niobate stator hindered the stable friction drive operation. We indicated that the conductivity improved lithium niobate, by chemical reduction, would then eliminate the unstable reason i.e. the contact electrification. The severe failure of the stator surface sets the limit to the durability of the surface acoustic wave motor. Owing to the chemical inertness of lithium niobate, the surface failure of the stator was arisen from the mechanical stresses developed by the indentation and sliding of the projections placed at the slider surface. The sharp edge of projections, as fabricated, easily causes the failure. Thereby, wearing off procedure before the operation is proposed as only feasible method, if the projections are necessary. Nevertheless, the optimum geometry to prevent surface failure was deduced as flat plane.