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X-ray diffraction of the satellite distribution that surrounds the main reflection in single Bi2Sr2CaCu2Oy crystals revealed that incompatible reflections in the crystals associate with the mosaic block spread to affect satellite distribution in the reciprocal space. The diffraction profiles of nitrogen annealed crystals with high orientation reveal a structural modification corresponding to the Bi2Sr2CaCu2Oy phase of the crystals. The modification is independent of excessive oxygen atom concentration in the crystal layers.

X-ray diffraction and scanning electron microscopy provide a systematic study of the phase decomposition in the surface of Bi2Sr2CaCu2Oy single crystal. The Bi2Sr2CaCu2Oy are annealed in air at a temperature range of 400 to 750 degrees centigrade. The crystals decompose at a very low temperature of 450 degrees centigrade. During each phase of decomposition, three different compounds, bismuth oxide, strontium bismuth oxide and Bi2Sr2CuOx are obtained from the Bi2Sr2CaCu2Oy single crystals. Each phase depends on external temperature.

Influence of annealing on the superconductivity of single crystal Bi2CaCu2O(8+y) is analyzed with the help of a microprocessor. The examination is conducted in reducing and oxidizing atmosphere at 400-750 degrees Celsius. Superconductivity is increased due to the oxygen loss which is initiated by annealing in either flowing nitrogen or flowing oxygen gas. High oxygen pressure and annealing at 500 degrees Celsius suppress the increase in supeconductivity.

Annealing treatments at temperatures more than 500 degrees centigrade cause surface phase decomposition in big and good quality Bi2Sr2CaCu2O7 single crystals. The amount of oxygen present in the annealing atmosphere influences the change of structure in the surface of the single crystals, for which, evaporation of the Bi in the crystals is also essential. For the double BiO layers also, the evaporation of Bi in the crystals is needed.