Synthesis, thermal and electrical properties of Al-doped Bi4V1.8Cu0.2O10.7

Partial substitution of copper with aluminum in Bi4V1.8Cu0.2O10.7 has led to the Bi4V1.8Cu0.2−xAlxO10.7+x/2 solid solution. X-ray diffraction and thermal analysis have shown that the compounds with x=0.05 and x=0.10 are tetragonal with γ′ form of Bi4V2O11, while the compound with x=0.15 is of β polymorph. The effect of Al3+ doping on electrical conductivity has been studied using Electrochemical Impedance Spectroscopy. The electrical conductivity of doped samples along with the amount of Al3+ has been studied by electrochemical impedance spectroscopy in the temperature range 250–700 °C. The slope changes observed in the Arrhenius plots agree with the microstructural transitions occurring in these compounds. The highest ionic conductivity values are obtained for the sample with x=0.05

Synthesis, sintering and electrical properties of P-doped Bi₄V₂O₁₁ ceramics

Partial substitution of vanadium by phosphorus in Bi4V2O11, compound belonging to the Aurivillius family, leads to the formation of Bi4V2−xPxO11 solid solution with an orthorhombic symmetry and does not stabilize the γ-high temperature form down to room temperature. X-ray diffraction, density measurements, thermal analysis and IR spectroscopy have been used to confirm the formation of the solid solution. The influence of sintering temperature on the microstructure and the grains size of the samples with different compositions was investigated by the scanning electron microscopy (SEM). The evolution of the electrical conductivity with phosphorus ratio has been investigated by impedance spectroscopy and correlated to the structural transformations

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 Bi4V1.8Cu0.2−xCoxO10.7 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