Abstract
Crystals grown using static and rotary crucibles from mixtures of analytical grade Bi 2O 3, Sr(OH) 2·8H 2O, CaCO 3 and CuO had nominal compositions Bi 2Sr m Ca n Cu p O q (1.5 < m ≤ 2.0, 0.2 < n ≤ 2.0, 1.8 < p < 3.0), were characterized by X-ray powder diffraction and scanning electron microscopy, and contained intergrown crystals of Bi 2Sr 2CaCu 2O 8 (2212) and Bi 2Sr 2CuO 6 (2201) in various relative amounts, together with crystals of CuO, (Sr, Ca) 2CuO 3 and Sr(Cu, Bi)O 2. The intergrowths of 2212 and 2201 with highest 2212 contents were obtained from melts at 980°C of mixtures with m = p = 2 and n = 1, using rotary crucibles and a cooling rate of 0.5°C h -1. After being recrystallized, crystals of 2212 appeared free of even traces of 2201, were orthorhombic, had cell dimensions of a = 5.404(2) A ̊ , b = 5.418(4) A ̊ and c = 30.80(3) A ̊ , and showed a superconducting transition at 90 K as indicated by magnetization measurements. The crystal structure of one orthorhombic Sr(Cu, Bi)O 2 crystal of unit-cell constants a = rm3.4865(5) A ̊ , b = rm16.176(2) A ̊ and c = rm3.8818(4) A ̊ was refined in the space group Cmcm arriving at the composition Sr(Cuin0.85Bi0.15)O 2.225, R = 0.037, and the main distances and angles which are given.
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