Changes in a fractional site occupancy as an effect of an oxygen ordering on the basal CuO plane in YBa2Cu3Ox

X-ray diffraction and thermogravimetric (TGA) studies have been carried out on orthorhombic YBa 2 Cu 3 O x samples obtained by the reoxygenation of tetragonal samples. Thermogravimetric measurements performed in 100% oxygen provided data for the oxygen content (x) on the CuO basal planes. At fixed x higher than 6.8, samples obtained by different final heat treatments show different amounts of orthorhombic distortion (higher values for samples with higher degree of ordering). The orthorhombic distortion and oxygen content data have been used for the estimation of fractional site occupancy of O(1) and O(5) sites ∗ ∗ The site notation is the same as in Jorgensen's et al. 2 paper. of YBa 2 Cu 3 O x on the basis of Bakker's et al. 8 theory. Differences in fractional site occupancy are obtained for samples with different degree of ordering.