Sequence of phase transitions in a quasi-one-dimensional β-Na0.33V2O5 compound with variable valence

The thermal properties-specific heat, thermal conductivity, and thermal expansion coefficients-of a single crystal of quasi-one-dimensional variable-valence beta-Na0.33V2O5 compound were studied. With lowering temperature, it sequentially undergoes the structural (T-S similar to 230 K), charge (T-C similar to 136 K), and magnetic (T-N similar to 22 K) phase transitions. The structural transition at T-S, resulting in the ordering of the Na ions, and the charge ordering at T-C, resulting in the charge redistribution over the positions of V ions, are accompanied by the anomalies in the temperature dependences of all the studied properties. The magnetic ordering at T-N results in the appearance of the canted antiferromagnetic structure and manifests itself only in the anomaly in the temperature dependences of the thermal expansion coefficients. (C) 2004 MAIK "Nauka / Interperiodica".