Optimum in the thermoelectric efficiency of nanostructured Nb-doped TiO ceramics: from polarons to Nb-Nb dimers.

Rutile is the most common and stable polymorph form of titanium oxide TiO2 at all temperatures. The doping of rutile TiO2 with a small amount of niobium is reknown for being responsible for a large increase of the electrical conductivity by several orders of magnitude, broadening its technological interest towards new emerging fields such as the thermoelectric conversion of waste heat. The electronic conduction has been found to be of a polaronic nature with strongly localized charges around the Ti3+ centers while, on the other side, the relatively high value of the thermal conductivity implies the existence of lattice heat carriers, i.

Heteroleptic Tin(IV) Aminoalkoxides and Aminofluoroalkoxides as MOCVD Precursors for Undoped and F-Doped SnO Thin Films.

A series of asymmetric and potentially bidentate amino alcohols and amino fluoro alcohols (ROH) having a different number of methyl/trifluoromethyl substituents at the α-carbon atom, [HOC(R)(R)CHNMe] (R = R = H (dmaeH); R = H, R = CH (dmapH); R = R = CH (dmampH); R = H, R = CF (F-dmapH); R = R = CF (F-dmampH)) have been used to develop new monomeric and heteroleptic tin(IV) amino(fluoro)alkoxides [Sn(OR)(OR)] (R = Et, Pr, Bu). These new complexes, which were thoroughly characterized by spectroscopy (IR and multinuclei NMR (H, C, F, and Sn)) as well as single-crystal X-ray studies on representative samples, were investigated for their thermal behavior to determine their suitability as MOCVD precursors for the deposition of metal oxide thin films. The two most suitable compounds, [Sn(OBu)(dmamp)] and [Sn(OBu)(F-dmamp)], were used in a direct liquid injection chemical vapor deposition (DLI-CVD) process to deposit undoped SnO and F-doped SnO thin films, respectively, on silicon and quartz substrates.