Propriétés de transport dans les bronzes de tungstène substitués au tantale

Abstract
Transport properties of tungsten bronzes doped with tantalum The thermoelectric power of several Na x Ta y W 1−y O 3 , bronzes have been measured between 4.2 and 900 K. As the number of d electrons decreases, a metal-non-metal transition occurs, which is ascribed to Anderson localization. The transport properties of the non-metallic samples are described in terms of three different hopping mechanisms at the Fermi level. With rising temperature first variable-range hopping, then Miller–Abrahams and finally Heikes hopping successively prevail.