paramagnetic Mn3O4 kelvin superconductivity temperature superconductive nanostructured Nb3Sn cuprates polycrystalline polyimide kelvins nitride ferroelectric gallium superhard paraelectric YBa2Cu3O7 piezoelectric semiconductor MINDO diboride alloys arsenide ferroelectrics resistivity cuprate magnetization germanium Tg annealing silicon superconduct Fe3O4 Polycrystalline polymer dielectric crystalline