High-temperature X-ray study and oxygen disordering mechanism in high-pressure phases Sr1-xNdxCuO2 (x=0.10, 0.13)

The thermal stability and oxygen disordering mechanism in high-pressure inf inite-layer (IL) phases Sr1-xNdxCuO2 (x = 0.10, 0.13) was studied by in sit u high-temperature X-ray diffraction and thermal analysis. The oxidation in air or oxygen starts at 400 degrees C with the formation of a 8 : 8 : 16 delta (delta similar to 2) phase. In purified helium, the IL phase is stab le up to 700 degrees C; however, disordering in the oxygen sublattice start s at 400 degrees C, involving the transfer of part of the oxygen atoms from a CuO2 layer to an Sr(Nd) layer. The oxidation of the IL phase to the 8 : 8 : 16 + delta (delta similar to 2) phase occurs in two stages: Stage I inv olves IL phase disordering, and stage II involves oxidation of the disorder ed IL phase to a phase of the 8 : 8 : 16 + delta family.