Syntheses of hollandite type Rb 2Cr 8O 16, K 2Cr 2V 6O 16 and K 2V 8O 16

Abstract

Hollandite-type compounds, Rb 2Cr 8O 16, K 2Cr 2V 6O 16 and K 2V 8O 16, were synthesized under high P-T conditions up to 1200°C and 7GPa. The structural refinement using a single crystal of Rb 2Cr 8O 16 confirms that the structure is similar to that of K 2Cr 8O 16. Magnetic measurements indicate that Rb 2Cr 8O 16 is ferromagnetic below 295K, K 2Cr 2V 6O 16 paramagnetic down to 77K and K 2V 8O 16 has susceptibility anomaly at 175K. These compounds are all semiconductive and show discontinuities in temperature-resistivity curves at points corresponding to magnetic anomalies.