Described is an article including a sapphire substrate carrying a superconductive layer of a compound of the formula YBa2Cu3O7-x (YBCO), the layer having surface area of at least 10 cm2, and critical current of at least 100 A/cm width at a temperature of 77K or higher. In one exemplary embodiment, the thickness of the superconductive layer is between 10 nm and 50 nm. In another exemplary embodiment, the thickness of the superconductive layer is more than 600 nm. In preferred embodiment, an YSZ layer and a non-superconductive YBCO layer separate between the superconductive layer and the substrate.