Low-temperature synthesis of binary cuprates from hydroxide precursor

Binary cuprates of Sr₂CuO_3+δ and SrCuO₂ have been synthesized at low temperatures below 500°C under various values of partial oxygen-pressure P_O2 by thermal decomposition of hydroxide precursors, Sr₂Cu(OH)₆ and SrCu(OH)₄, respectively. The tetragonal Sr₂CuO_3+δ (δ ∼ 0.3) is obtained by the heat-treatment at 400°C and P_O2 ≥ 0.2 atm. The value of δ appears to be independent of P_O2 and unchangeable. On the other hand, the orthorhombic Sr₂CuO_3+δ (δ ∼ 0) is obtained by the heat-treatment at 400°C in flowing gas of N₂. For 0 < P_O2 < 0.2 atm, a mixture of the tetragonal and orthorhombic phases is obtained. The orthorhombic SrCuO₂ is obtained by the heat-treatment at 500°C in flowing gas of N₂, although the tetragonal SrCuO₂, namely, the so-called infinite-layer compound is not obtained.