High pressure synthesis of cuprate perovskites

Abstract

As members of the ABO 3 family of oxides, the Ln 4Cu 3MoO 12 family of compounds (LnLa, Pr, Nd, and Sm) all crystallize in the rare-earth hexagonal structure at ambient pressure. At 6 GPa and 1200 K they transform to layered perovskite structures which are ∼ 15% more dense than their ambient pressure variants. The high-pressure phases exhibit two-dimensional antiferromagnetic ordering above 200 K, which is indicative of pure copper-oxygen layers. The lanthanum analogue can be doped with up to 25% strontium, (La/Sr) 4Cu 3MoO 12. A large decrease in resistivity is observed with doping but the compound does not become metallic or superconducting.