Synthesis and magnetic properties of (Ba,Bi)1.54Rh8O16 hollandite

The synthesis, structure and electrical and magnetic properties of (Ba,Bi)1.54Rh8O16 hollandite are discussed. The addition of Bi stabilizes the Ba-Rh hollandite, otherwise not found under our synthesis conditions. The compound crystallizes in the monoclinic space group I2/m, a = 9.425(5) Å, b = 10.425(4) Å, c = 3.160(1) Å, γ = 94.11(5). Electron diffraction and structure imaging show that the (Ba,Bi) columns along the tunnels are incommensurate with the Rh8O16 framework, and analysis of the electron diffraction and elemental analysis allow the formula to be determined as Ba1.21Bi0.33Rh8O16. The compound shows Curie–Weiss paramagnetism, and we compare its susceptibility to that of Rh2O3. Polycrystalline samples show a negative dρ/dT between 0.3 and 300 K. No superconductivity is observed down to 0.3 K.