Sol-gel synthesis and electrical characterization of doped-carbon decorated mixed conductor ceramics

New mixed composite conductors of compositions: Li3V2-x [Cu](x) (PO4)(3)/C and Li3V2-x [Nb](x)(PO4)(3)/C (x = 0.1; 0.2 and 0.3) have been synthesized by the sol-gel method using Citric and Oxalic acids as a primary carbon source and Carbon Black or Carbon Nano-Fibers as secondary carbon sources. The combination of these carbon forms with the Nb doped-polyanion material boosts their electrical behavior up to 10(-3) S.m(-1) that is two orders of magnitude higher than the Li3V2(PO4)(3)/C at a room temperature. SEM, TEM and Micro-Raman Spectroscopy evidence that Carbon Nano-Fiber blend is better conductor than Carbon Black blend, which is also revealed by complex conductivity spectra. The conductivity behavior of Nb-doped ceramic is better than the Cu-doped one. The obtained niobium composites have a much more stable structure compared to the copper ones because the niobium atoms fit well in the vanadium position, whereas copper atoms are expelled from the structured.