Study on structural, thermal, sintering and conductivity of Cu-Co doubly substituted Bi4V2O11

Doubly substitution of vanadium by Cu and Co in the limit of 10% in Bi₄V₂O₁₁, has led to the formation of the Bi₄V_1.8Cu_0.2−xCo_xO_10.7 solid solution. X-ray diffraction shows that all the compositions present a tetragonal symmetry. The thermal analysis has revealed that the polymorph γ' phase, which is formed by a partial ordering of oxygen ions in the γ high temperature form, is stabilized at room temperature. The influence of sintering temperature on the microstructure of the samples was investigated by the scanning electron microscopy (SEM). The ceramics sintered at 820 °C for more than 3 hours present micro-craks. The evolution of the electrical conductivity with temperature and the degree of substitution has been investigated by impedance spectroscopy. The sample with x=0.1 presents the highest value of the conductivity ≈4.6×10⁻² S·cm⁻¹ at 600 °C.