Chemical diffusion of water in the double perovskites Ba4Ca2Nb2O11 and Sr6Ta2O11

BaCeO3: Materials development, properties and application

“…The optimal pH of the solution was found to be 13 since under these conditions all the ions from the solution were deposited together in the form of the corresponding hydroxides. In general, for the deposition process to complete, the conditions for all elements to transfer from the solution to an insoluble form, and the pH value of the solution attributed to this transition, must be taken into account [84,91]: (35) In Table 6, the technological parameters of the powder's preparation by the co-precipitation method are listed. The presented data confirm that this method can be successfully applied to obtain high reactive nanoscale and sub-micron powders, which can be used in the production of gas-tight cerate ceramics using lower temperatures and a lower sintering time.…”

“…High-temperature proton conductivity in SrZrO 3 -based materials was first found in 1980 by the group of Iwahara [27], and later -in other perovskites of A 2+ B 4+ O 3 type such as SrCeO 3 [5] and BaCeO 3 [28]. Further investigation showed that proton conductivity is also typical of perovskites of different types: A 1+ B 5+ O 3 (for example, KTaO 3 [29]), A 3+ B 3+ O 3 (for example, LaScO 3 [30,31]) and other related perovskite structures, such as: Ba 2 In 2 O 5 [32,33], Sr 6 Ta 2 O 11 [34,35] and Ba 4 Ca 2 Nb 2 O 11 [36]. In all cases the structure of the oxide is capable of attaining relatively high concentrations of oxygen vacancies whose interaction with water vapor leads to the appearance of proton defects in the crystal structure and hence oxygen ionic and proton (co-ionic) conductivity.…”

Incorporation of Water and Fast Proton Conduction in the Inherently Oxygen‐Deficient Compound La26O27□(BO3)8

“…The second class comprises compounds that, without dopants at all, have a deficiency in the oxygen sublattice. Examples are: the Brownmillerite compound Ba 2 In 2 O 5 & (& indicates that there is one oxygen vacancy per formula unit), a vacancy-ordered variant of the perovskite, which becomes disordered above the Brownmillerite-cubicperovskite transition temperature; [1] the Aurivillius-type Bi 4 V 2 O 11 & phase, with an ordered arrangement of oxygen vacancies in the low-temperature a form, [2] becoming disordered in the b and c forms; [3] the complex anion-disordered perovskites Sr 6 Nb 2 O 11 & [4] and Sr 6 Ta 2 O 11 &, [5,6] ; and the fluorite-type compound d-Bi 2 O 3 &. [7] A number of these oxygen-deficient oxides have been found to dissolve significant amounts of protons by equilibration with water vapor (or already during solid-state synthesis when they are cooled down in ambient air), involving the filling of oxygen vacancies and the replacement of their effective positive charge by protons as hydroxide ions.…”

Dopant substitution and oxygen migration in the complex perovskite oxide Ba3CaNb2O9: A computational study

“…Hence, one could be below the percolation threshold, but still have regions that are separated from one another, within which there are connected paths of NbO 6 octahedra. This would explain why the available experimental data on oxygen transport in Ba 3 Ca 1.18 Nb 1.82 O 9À3x/2 give activation energies of 0.82-0.92 eV [35] and 0.7 eV [36], which can only refer to the migration of oxygen vacancies around NbO 6 octahedra. In this regard it would be of great interest to determine the d.c. conductivity data in dry samples or to measure the diffusion of isotopically labelled oxygen.…”