Abstract: A polycrystalline bulk body of this invention has uniformity in superconducting properties, in comparison to a polycrystalline bulk body including crystal grains each constituted by (Ba1-xKx)Fe2As2. A polycrystalline bulk body (1) of this invention includes crystal grains each constituted by an iron-based compound (10) expressed by chemical formula AA?Fe4As4, where A is Ca and A? is K, the iron-based compound (10) having a crystal structure in which AFe2As2 layers (16) and A?Fe2As2 layers (17) are alternately stacked.

Abstract: The object of the present invention is to provide a compact and inexpensive single-crystal growth apparatus. The single-crystal growth apparatus of the present invention which comprises spheroid mirrors 11, 12, heat sources 13, 14 located at the one foci F1, F2 of the spheroid mirrors 11, 12, a quartz tube 16 enclosing a heating zone 15 of the common focus F0 on the other side, and, in the quartz tube 16, a feed rod 18 supported by an upper crystal drive shaft 17 and a seed crystal rod 20 supported by a lower crystal drive shaft 19. The interfocal distance between the foci F1, F2 and the foci F0 is made 41.4-67.0 mm and the minor axis/major axis ratio of the spheroid mirrors is set to 0.90-0.95.