Single crystal specimens of LaMo8-xO14 (x = 0 and 0.3) suitable for transport property measurements have been prepared by electrolyzing fused mixtures of sodium and rare earth molybdates. Electrical resistivity measurements with the current parallel to the ab plane of LaMo8-xO14 containing the quasi-discrete units of Mo8 clusters showed semiconducting behavior down to 20 K for both compounds. The electrical resistivity in the ab plane (ρ300Kab = 5 × 10-3ohm · cm) of LaMo7.70O4 is an order of magnitude smaller than the corresponding value for the fully stoichiometric compound (ρ300Kab = 4.4 × 10-2 ohm · cm). Furthermore, the ρ300Kab of La Mo7.70O14 is a factor of 4 lower than that measured along the c-axis (ρ300Kc = 2 × 10-2 ohm · cm) implying quasi-low-dimensional behavior. The thermal activation energy for electrical conductivity estimated from the lnρ vs 1000/T plots showed a significant decrease near ∼70 K and 130 K for LaMo7.70O14 and LaMo8O14, respectively. The magnetic susceptibility data collected on a batch of randomly oriented crystals revealed the presence of local moments in LaMo7.7O14, while the stoichiometric analogue was diamagnetic. The semiconducting nature of the LaMo8-xO14 phases may be attributed to the unfavorable intercluster distance (3.08 Å) as well as positional and configurational disorder of the Mo8 clusters.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry