Synthesis, Crystal Structure, and Optical Properties of Layered Perovskite Scandium Oxychlorides: Sr2ScO3Cl, Sr3Sc2O5Cl2, and Ba3Sc2O5Cl2

Synthesis and Characterization of Oxide Chloride Sr2VO3Cl, a Layered S = 1 Compound

The mixed-anion compound with composition Sr₂VO₃Cl has been synthesized for the first time, using the conventional high-temperature solid-state synthesis technique in a closed silica ampule under inert conditions. This compound belongs to the known Sr₂ TmO₃Cl (Tm = Sc, Mn, Fe, Co, Ni) family, but with Tm = V. All homologues within this family can be described with the tetragonal space group P4/nmm (No. 129); from a Rietveld refinement of powder X-ray diffraction data on the Tm = V homologue, the unit cell parameters were determined to a = 3.95974(8) and c = 14.0660(4) Å, and the atomic parameters in the crystal structure could be estimated. The synthesized powder is black, implying that the compound is a semiconductor. The magnetic investigations suggest that Sr₂VO₃Cl is a paramagnet at high temperatures, exhibiting a μ_eff = 2.0 μ_B V^-1 and antiferromagnetic (AFM) interactions between the magnetic vanadium spins (θ_CW = -50 K), in line with the V-O-V advantageous super-exchange paths in the V-O layers. Specific heat capacity studies indicate two small anomalies around 5 and 35 K, which however are not associated with long-range magnetic ordering. ³⁵Cl ss-NMR investigations suggest a slow spin freezing below 4.2 K resulting in a glassy-like spin ground state.

Synthesis, chiral crystal structure, and magnetic properties of Ba3Ga2O5Cl2

A new compound, Ba₃Ga₂O₅Cl₂, isostructural with Ba₃Fe₂O₅Cl₂, was synthesized by solid-state reaction in air. Through single-crystal and powder X-ray diffraction analysis, the crystal structure was determined to be cubic with chiral space group I2₁3 and unit-cell parameter a = 9.928 (1) Å. The Ga³⁺ ions in Ba₃Ga₂O₅Cl₂ are coordinated by O atoms and form GaO₄ tetrahedra. Ten neighboring GaO₄ tetrahedra are further bridged through corner sharing and rotation along the body diagonal, producing the chiral structure. Magnetization measurements indicate temperature-independent diamagnetic behavior, which is qualitatively consistent with core diamagnetism from all the constituent elements.