We report on results of systematic X-ray investigations of the Bi2Sr2CaCu2O8+x (2212) single crystals grown by slow cooling, top seeded solution growth and travelling solvent floating zone (TSFZ) methods. The typical concentrations of dislocations in the Bi-2212 crystals are estimated from width of peaks. According to the obtained X-ray topography and diffractometry data, these crystals demonstrate misorientation anisotropy around different crystallographic axes, which is a consequence of incommensurate modulation in this compound. The highly perfect crystals grown by TSFZ method are found to demonstrate the abnormal transmission X-ray diffraction effect (Borrman effect).

An electrodynamic technique is developed for determining the components of surface impedance and complex conductivity tensors of HTSC single crystals on the basis of measured quantities of a quality factor and a resonator frequency shift. A simple formula is obtained for a geometrical factor of a crystal in the form of a plate with dimensions b>a>c in a microwave magnetic field H(omega)perpendicular toab. To obtain the c-axis complex conductivity from measurements at H(omega)parallel toab, we propose a procedure that takes into account of sample size effects. With the aid of the technique involved temperature dependences of all impedance and conductivity tensors components of YBa2Cu3O6.95 single crystal, grown in BaZrO3 crucible, are determined at a frequency of f=9.4 GHz in its normal and superconducting states. All of them proved to be linear at T<T-c/2, and their extrapolation to zero temperature gives the values of residual surface resistance R-ab(0)approximate to40 muOmega and R-c(0)approximate to0.8 m Omega and magnetic-field penetration depth lambda(ab)(0)approximate to150 nm and lambda(c)(0)approximate to1.55 mum.

The temperature dependence of the lattice constants a, b and c of YBa2Cu3O7−δ(δ=0.5) has been determined in a range 28–300 K by high-angle double-crystal X-ray diffractometry, and examined near the superconducting transition temperature Tc=55 K. The angle φ that is related to the orthorhombicity of the crystal as φ=tan−1(a/b) decreases with decreasing temperature; it is found, however, that at Tc the decrease starts to slow down. The difference between φ observed and that extrapolated from the normal state is proportional to (1−T/Tc)ξ. This is new behaviour in connection with the onset of superconductivity, and is discussed in terms of a change in the bond strength around Cu atoms. By comparing the results with that of a specimen with δ∼0.2(Tc∼90K) in literature, it is shown that, owing to weaker bond strength around Cu atoms, the crystal with δ=0.5 exhibits the behaviour more clearly.

We report the phase transformation resultant from annealing of Bi-2212 single crystals doped by Pb (Pb0.3 per formula unit) under elevated oxygen pressure. General Tc vs. pO2 dependence plotted by us in the range 7×10−6 to 115 atm demonstrates a sharp bend. This knee indicates the phase transformation at annealings under pO2>1 atm. The X-ray topography data suggest that in addition to the phase of Pb-type modulation ( q =0.131 b * ) this transformation gives rise to another phase of Bi-type modulation ( q =0.200 b * + c * ). This process is reversible. We observed on individual crystals the twinning system analogous to that known for La2−xSrxCuO4 crystals.

Temperature dependences of the electrical resistivity measured in the CuO2 plane (rho (ab)) and along the c axis (rho (c)) and of the anisotropy coefficient rho (c)/rho (ab) of volume nonsuperconducting Nd2-xCexCuO4+delta (x = 0, 0.12, 0.15, 0.17, and 0.18) were studied in a temperature range of 1.7-300 K. It was found that doping with cerium changes not only the value of the electrical resistivity but also the behavior of its temperature dependence from the activational at x = 0 to metallic at x greater than or equal to 0.15. The dependence of the anisotropy coefficient rho (c)/rho (ab) on the cerium content and temperature is likely to be related to the change from three-dimensional to two-dimensional conduction with decreasing temperature or cerium content.

The conditions of synthesis of monodisperse SiO2-spheres sizing between 100 and 1600 nm are determined. The method of natural sedimentation combined with capillary contraction is used to obtain uniform monolayers of ordered SiO2-spheres with the area of several cm(2) on glass substrates. The micro-structure of produced films is studied by means of electron and optical microscopy, and by optical diffraction. Typical sizes of the ordered sites (domains) in the films range between 10 and 50 mum. The maximal size of domains reaches 600 mum. The cell parameters and the sizes of the ordered regions are determined. The domain structures with bonds of ordered orientation are found.

By using the modified Top Seeded Solution Growth technique high quality Nd2−xCexCuO4 single crystals with homogeneous cerium distribution and sizes up to 10×10×2 mm have been prepared in Pt crucibles. It was revealed that the anisotropy of the growth rates in (001) plane and in [001] direction depends from growth temperature and equals 70 for 1050°C, 15 for 1115°C and 5 for 1150°C. It was found that Pt dissolves in NCCO single crystals and completely suppresses superconductivity at the concentration 0.02 at./f.u. Although Nd1.82Ce0.18Cu0.98Zr0.02Oy and Nd1.87Ce0.13CuOy single crystals obtained by the slow cooling method in YSZ and Al2O3 crucibles demonstrate the superconductivity transitions with Tc=20 K and Tc=22 K but it was shown that ceramic crucibles are not stable and completely corroded within several days. The Borrmann effect was observed on the explored crystals.

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