Characterisation of Incommensurate Bi2+xSr2-xCuOz by X-Ray Powder Diffraction and Oxygen Content Determinations

Abstract
The composition-temperature stability region of the solid solution Bi2+x Sr2-x CuO z , phase R, has been determined. At 800°C, 0.15<xxa=b=5.390(1), c=24.59 Å, with a supercell vector q * given by q *=n δb *-n ε c *, where δ=0.21, ε=0.55, for x=0.30 and n=1, 2 …. Both a and ε increased with x, c decreased with x and δ was independent of x. The excess oxygen content, α, was determined to be (0.18±0.02) by citrate iodometry and was independent of x. The total oxygen content z, given by z=6+x/2+α, was confirmed to be 6.33±0.04, for x=0.30, by hydrogen reduction thermogravimetry.