Texture of Y- and Bi-HTSC and Methods for its Determination

Investigation of the texture of Y‐ and Bi‐HTSC materials by X‐ray techniques involves certain difficulties owing to the peculiarities of their crystal structure which causes the arrangement of reflexes in dense groups and practically precludes the formation of a pole figure from an isolated reflex. The texture of Y‐ and Bi‐HTSC materials has been investigated by constructing direct pole figures in an automatic texture diffractometer DAPT YM 1 in CuKα emission from groups of reflexes which are unresolvable under the test conditions. The choice of groups of reflexes was dictated by the type of texture formed. With a basal texture of packing of powders, the following groups have turned out to be the most suitable for the YBa2Cu3O7–x phase (123): (013) + (110) + (103), 2θ = 32.3 – 32.8º and (014) + (005) + (104), 2θ = 38.5 – 38.8º. They include the reflexes which are structural and superstructural relative to a bcc subcell with a rather slight orthorhombic distortion, with its tripling along the “c” axis forming a cell of (123) compound. For the Bi2Sr2CaCu2O8 phase, there have been used the groups of reflexes (008) + (111) + (1.4/54), (0.0.10) + (1.6/5.4) + (0.9/5.1), (0.0.12) + (1.6/5.8) + (204) + (119). (115) + (1.6/5.4) + (0.1/5.9), and (117) + (0.9/5.1) + (1.6/5.6) + (1.4/5.8), 2θ with respectively 23.2 – 24.0º, 29.1 – 29.7º, 35.1 – 35.2º, 36.5 – 28.4º, and 29.7 – 31.4º. They also include reflexes from the lattice constructed by multiplication of a perovskite cell with α = 5.40 Å, b = 5.41 Å and c = 30.6 Å along the “b” axis. Y‐HTSC‐based materials also contain a component of shear texture which is close to such a texture in bcc metals. The texture of Y‐ and Bi‐HTSC materials is relatively stable in hightemperature annealing. The nature of the effect of annealing at moderate temperature is different. Russian text ignore.