Superconductivity in bulk T′-(La,Sm)2CuO4 prepared via a molten alkaline hydroxide route

Abstract We have synthesized La 2− x Sm x CuO 4 (0 ⩽ x ⩽ 2.0) with the Nd 2 CuO 4 structure via a molten alkaline hydroxide route at temperatures as low as 400–480 °C. After reduction heat treatment in vacuum at 600–750 °C for removal of excess oxygen atoms at the interstitial apical site, superconductivity with T c = 20–24 K was observed in the samples with x = 0.05–1.0. The superconducting volume fraction is nearly 100% for x = 0.3–0.7. Our results demonstrate that La 2− x Sm x CuO 4 with no nominal carrier doping is a bulk superconductor.