High-pressure evolution of novel R2CuTiO6 (R = Tb – Lu) perovskite phases

• Published in: Solid state sciences 2024-05, Vol.151, p.107514, Article 107514
• Main Authors: Sederholm, Linda, Gilioli, Edmondo, Delmonte, Davide, Yamamoto, Ayako, Karppinen, Maarit
• Format: Article
• Language: English
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2024.107514

Perovskite oxides of the R2CuTiO6 type with a trivalent rare earth element (R) at the A-cation site and co-occupancy of the B-cation site with the Jahn-Teller d9 Cu2+ and d0 Ti4+ transition metals, provides an interesting playground for various chemical and physical phenomena. However, conventional solid-state synthesis under ambient-pressure (AP) yields the perovskite structure only for the largest R constituents from La to Gd; with the smaller rare earth elements (Y, Tb–Lu) a non-perovskite (hexagonal BaTiO3-type) structure is formed. Here we demonstrate that through high-pressure (HP) high-temperature treatment, the hexagonal AP structure can be converted into a distorted (orthorhombic) perovskite structure for all the smaller R constituents. The critical pressure needed for the conversion increases with decreasing R3+ ion size, up to ca. 6 GPa for R = Lu. Moreover, a novel intermediate phase is found to form for most of the R constituents when pressures lower than the critical pressure are applied. We have employed both X-ray diffraction and UV–vis spectroscopy analyses to systematically follow the phase formation schemes for the different R constituents. [Display omitted] •Hexagonal R2CuTiO6 phases with smallest Rs are converted to perovskites via high pressure treatment.•This extends the R2CuTiO6 perovskite series to cover all Rs from La to Lu.•Turning point is found around R = Tb–Gd for lattice parameters versus R size behaviour.•Critical pressure required for the conversion increases with decreasing R size.•New intermediate phases are found to form in the lower-pressure range before the perovskites.