Particle size effect on the electronic conductivity of electroactive LixWO3•H2O powders:: A study from 103 to 1010 Hz

We report on the electrical transport properties and the permittivity of LixWO3 center dot H2O powders which may be used as infrared reflectivity modulators. Broad-band dielectric and resistivity spectra of LixWO3 center dot H2O powders were recorded in a frequency range of 10(3)-10(10) Hz at temperatures varying between 200 and 300 K. The role of the powder morphology has been investigated on two types of compounds, the first one being constituted by nanoparticlcs and the second by microparticles. Complex resistivity diagrams have enabled us to obtain thermal behaviors of both dc conductivity. The transport properties are shown be consistent with small-polaron conduction models. Particle size effect is evidenced, arising from the surface layer conduction of the nanoparticles. Two dielectric relaxations are found, attributed to water molecule motions and small-polaron hopping in Li0.35WO3. A discussion is given concerning the different behaviors which have been observed.