The origin of the modulated structure in Sr2CuO3+δ (δ = 0.4): [CuO2] in‐plane oxygen vacancy or apical oxygen vacancy?

We propose the question of the modulated structures of copper oxide is caused by the [CuO2] in-plane oxygen vacancy or apical oxygen vacancy. Sr2CuO3+delta single-crystal samples were prepared using high-temperature and high-pressure methods. The major phase of Sr2CuO3+delta (delta = 0.4) single-crystal system is found to be constituted by the 5 root 2 a modulated structure with the Fmmm space group, which originates from the [CuO2] in-plane oxygen vacancy appearing in octahedral Cu-O. Besides, the presence of the [CuO2] in-plane oxygen vacancy may obliterate the superconductivity of the system. Experimental results deduce that the oxygen vacancy may appear in the apical oxygen sites in high-temperature copper oxide superconductors.