Doping Bi4V1.8Cu0.2O10.7 with niobium has led to the formation of the Bi4V1.8Cu0.2−xNbxO10.7+3x/2 solid solution. X-ray diffraction and thermal analysis have shown that only the compound with x=0.05 presents a tetragonal symmetry with a γ′ polymorph while the other compositions are of β polymorph. The influence of sintering temperature on the microstructure of the samples was investigated by the scanning electron microscopy (SEM). The ceramics sintered at temperatures higher than 820 °C present micro-craks. The evolution of the electrical conductivity with temperature and the degree of substitution has been investigated by impedance spectroscopy. Among all compositions studied the sample with x=0.05 presents the highest value of the conductivity.
