Crystal structure and conduction of BICUTIVOX

Existence boundaries, structure, and transport parameters were studied for Bi 4 V 2 − x Cu x /2 Ti x /2 O 11 − x solid solutions. Doping levels within x = 0.025–0.15 distort the C 2/ m crystal lattice (this lattice is characteristic of individual the Bi 4 V 2 O 11 phase) and lowers its symmetry to triclinic. The solid solutions with 0.25 ≤ x ≤ 0.30 crystallize in tetragonal space group I 4/ mmm . High-temperature X-ray diffraction and dilatometry measurements for Bi 4 V 2 − x Cu x /2 Ti x /2 O 11 − x ( x ≤ 0.35) solid solutions verified the existence of three structural varieties within 298–1023 K. Electrical conductivity of BICUTIVOX was studied by impedance spectroscopy as a function of temperature, composition, and oxygen partial pressure. Equivalent circuits of cells were analyzed. Features of electrical conductivity versus temperature for the structural varieties are noted. Above 873 K, the solid solutions samples with x = 0.05 have the highest conductivity. At lower temperatures, higher conductivities are in the solid solutions that retain the γ phase in the low-temperature region. The dominant oxygen-ion conduction mechanism was discovered in the solid solutions.