I. E. Animitsa

Electric properties of oxyfluorides Ba2In2O5−0.5xFx with brownmillerite structure

Synthesis of fluoro-substituted substances based on brownmillerite Ba2In2O5 is carried out. The width of the homogeneity region of the Ba2In2O5−0.5xFx (0 < x ≤ 0.25) solid solution was established using X-ray analysis. Measurement of temperature dependences of conductivity in atmospheres with different partial pressure of water vapor (pH2O = 3.3 and 2 × 103 Pa) showed an increase in conductivity at T ≤ 550°C in a humid atmosphere, which is due to appearance of proton transport. The dependence of conductivity on partial oxygen pressure (pO2 = 0.21 × 105 to 10−15 Pa) is studied in the temperature range of 500–1000°C; ion transport numbers are calculated. The method of polarization measurements was used to determine transport numbers of fluoride. Total conductivity is divided into ion (proton, oxygen, and fluoride ion) and electron components. Analysis of concentration dependences of conductivities showed that low concentrations of fluoride allow increasing both the total and partial conductivities (oxygen-ion and proton) and, besides, allow shifting the “order-disorder” phase transition by 100°C to the low temperature range.

Effect of anion doping on mobility of ionic charge carriers in solid solutions based on Ba2In2O5

In the work, mobilities of oxygen and protons are determined for F−-substituted solid solutions based on brownmillerite Ba2In2O5 and their concentration dependences are analyzed. It is found that small additives of the more mobile anion (F− ions) promote an increase in oxygen mobility as a result of additional effects of repulsion of ions of different nature in the anion sublattice. Mobility of oxygen at high fluoride concentrations decreases due to the overlapping of migration paths of diffusion, as both anions, fluoride ions and oxygen ions, move via oxygen vacancies. Concentration dependences of mobility of proton carriers have a similar character, which is related to the effect of the oxygen sublattice. The anion doping method used in the work can be recommended as the general method for improvement of the transport characteristics of oxygen-ionic and protonic conductors with a perovskite-like structure.

Proton and oxygen-ion conductivity of Ba4Ca2Nb2O11

Abstract The structure, conductivity and water uptake of the oxygen-deficient compound Ba 4 Ca 2 Nb 2 O 11 have been investigated. Ba 4 Ca 2 Nb 2 O 11 is found to crystallize in the cryolite structure with a =8.4449 A. The compound may be fully hydrated up to maximum water content approximately 1 mol H 2 O per mol Ba 4 Ca 2 Nb 2 O 11 , this process is accompanied by a reversible phase transformation due to formation of hydrate-like compound. In wet air, the temperature dependence of total conductivity shows a different behavior because of change in proton transport mechanism: small local maximum as a result of phase transformation ( T =350 °C), linear relationship with activation energy 0.55 eV at the temperature range 350–230 °C and 1.02 eV at lower temperature. A comparative analysis with Ba 3 Ca 1.18 Nb 1.82 O 9− δ was made.

Hydration and forms of oxygen-hydrogen groups in Oxyfluorides Ba2 − 0.5xIn2O5 − xFx

A number of fluorine-substituted compounds were synthesized from brownmillerite Ba2In2O5. The homogeneity range of the Ba2 − 0.5xIn2O5 − xFx solid solution (x ≤ 0.3) was determined by X-ray diffractometry. The studied phases were found to be able to incorporate water from the gas phase, due to which their orthorhombic structure transforms into tetragonal one. The degree of hydration decreased as the fluorine content in the solid solution increased. As in the case of Ba2In2O5, the energetically nonequivalent hydroxo groups were found to be the main form of oxygen-hydrogen groups.

Electrical properties of Ba2(In1-x Al x )2O5 solid solutions

The electric conductivity of perovskite-like Ba2(In1 − xAlx)2O5 solid solutions (0 < x ≤ 0.20) characterized by structural disordering in the oxygen sublattice was studied as a function of temperature and partial pressure of oxygen in an atmosphere with a low content of water vapors (

Synthesis, hydration, and electrical properties of oxyfluoride Ba2InO3F

p_{H_2 O}

Proton transport in perovskites Ba 2 InMO 6 (M = Nb, Ta)

= 3 × 10−5 atm). When In3+ was partially replaced by Al3+, the oxygen ion conductivity increased because of the disordering of oxygen structural vacancies, leading to a significant increase in the total electric conductivity of the samples.

Local structure and thermal properties of fluorine-doped perovskite related solid oxides

The electric conductivity of Ba2(In1–xAlx)2O5 (0 ≤ x ≤ 0.20) solid solutions was studied while varying the temperature and the partial pressure of oxygen in atmospheres with different humidities. The total electric conductivity was differentiated into components. In an atmosphere with high water vapor contents (PH2O= 2 × 10–2 atm) at temperatures below 600°C, these complex oxides proved to be ionic conductors with a predominant contribution of proton transfer.