Synthesis, Structure, and Physical Properties of RbCr2Se2O

Layered compounds containing the T2O plane (T = transition metal), which is the anti-type of the CuO2 plane in cuprate superconductors, have been explored widely because of their diverse physical properties. Among them, KV2Se2O has attracted much attention due to its interesting physical properties, especially the magnetic order. In this work, we report a new isostructural chromium oxyselenide, RbCr2Se2O. It was synthesized using a solid-state method using Rb2CO3 as the source of Rb and O for the title compound, with the assistance of Ba. The compound crystallizes in the space group P4/mmm with lattice parameters a = 4.01123(8) Å and c = 7.49357(18) Å. Magnetic susceptibility measurements indicate an antiferromagnetic transition at 345 K for RbCr2Se2O and also above room temperature, as the Néel temperature is TN ≈ 400 K for KV2Se2O. The analysis of variable temperature XRD data reveals the anisotropic thermal expansion of the RbCr2Se2O lattice. The almost unchanged lattice parameter a near the transition temperature and the broad peak with an onset temperature of ~360 K in the differential scanning calorimetry data may have a relationship with the magnetic ordering. The measurement of electrical resistivity demonstrates the semiconducting behavior of RbCr2Se2O. The thermal activation model and variable-range hopping model are proposed to describe the conduction mechanism in the high- and low-temperature ranges, respectively.