Electropolishing of polycrystalline YBa2Cu3O7-δ to meet the need for sharp needle geometry

An electropolishing method has been developed for preparing sharp needles from polycrystalline YBa2Cu3O7-δ by modifying a recipe for TEM specimen preparation. The method is characterized by a polishing temperature of below 0°C, a non-acidic electrolyt and an even removal of the constituent phases. An approach was employed of combining I-V measurements for polishing process and microscopical observation of surface morphology in finding optimum polishing conditions. TEM evidenced that no preferential attack appeared to grain boundaries. X-ray diffractometry and electron diffraction implied that no change in oxygen content occurred during electropolishing. The sharpness of the tip was examined by field-ion microscopy.