New experimental evidence of the structural modification in single crystal Bi 2Sr 2CaCu 2O y by X-ray diffraction observation

Abstract

The variations of the high angle 00 38 peak-shape by means of X-ray l scans of the 00 l fundamental reflections were investigated in detail for a highly oriented Bi 2Sr 2CaCu 2O y (Bi2212) crystal with sufficiently small intrinsic mosaicity and the same crystal annealed in air at 250, 300, 400, 600, and 750°C for 20 h in consequence. For the first time, we observed a new additional reflection almost overlapped original 00 l fundamental reflection at annealing temperature below 400°C by X-ray diffraction measurement, which shows that there coexisted two sets of lattice periodicity in the c-direction of the annealed crystal. The new additional reflection appeared at 250°C and disappeared at 400°C. Its intensity was increased at 300°C. The measurements of the AC susceptibility, c-axis parameter and full width at half maximum (FWHM) of the 00 38 peaks showed that the new additional reflection was associated with the oxygen diffusion in CuO 2 planes and the changes of strain field. The results provide the new experimental evidence that the structural distortion is more sensitive to the oxygen diffusion in CuO 2 planes than to that in Bi–O layers.