Hydrogen content in doped and undoped BaPrO3 and BaCeO3 by cold neutron prompt-gamma activation analysis

Abstract

Proton uptake in undoped and Y-doped BaPrO 3 has been measured by cold neutron prompt-gamma activation analysis, and compared to the proton uptake in Gd-doped BaCeO 3 , as determined by the same technique. The conventional proton incorporation model of perovskites in which oxygen ion vacancies, generated by the introduction of the trivalent dopant onto the tetravalent perovskite site, are filled with hydroxyl groups upon exposure of the sample to H 2 O containing atmospheres, predicts that the proton concentration in such materials should be no greater than the dopant concentration. In contradiction to this model, the proton concentration in BaPr 1−x Y x O 3 after humidification is as much as three times greater than the dopant concentration, and even undoped samples contain a high concentration of protons. Moreover, x-ray photoemission spectra suggest that the Pr oxidation state is lowered upon hydration. In contrast, BaCe 0.9 Y 0.1 O 3 shows a typical hydrogen concentration, of close to 90% of the yttrium concentration. The results are interpreted in terms of the variable valence of Pr, which can become reduced from the 4 + to the 3 + oxidation state upon exposure to water, and effectively behaves as a self-dopant within the structure.

Correlation between electroconductive and structural properties of proton conductive acceptor-doped barium zirconate

“…It has been reported that tetravalent Pr tends to become partially trivalent with a decrease in the partial pressure of oxygen. 27 The concentration of oxide ion vacancies increases for charge compensation, which benets the proton conduction.…”

Effects on the Proton Conduction Limiting Barriers and Trajectories in BaZr0.875Y0.125O3 Due to the Presence of Other Protons

“…The traditional mechanism for proton incorporation in perovskites is directly tied to the dopant concentration. 15,27) When an ABO 3 perovskite is doped at the tetravalent B sites with trivalent ions, an oxygen vacancy results for every two doped sites. This vacancy dissolves water from the atmosphere into a hydroxyl, which fills the vacancy and a proton which quickly binds to an oxygen in the perovskite lattice.…”

Electronic Structure of BaPr_1-<i>x</i>Yb_<i>x</i>O_3-<i>δ</i> by Soft-X-Ray Spectroscopy

“…Perovskite-type oxide BaPrO3 has an orthorhombic structure (Pbnm) with the lattice constant of a=6.201 Å, b=6.173 Å and c=8.712 Å at room temperature [1][2][3][4][5]. The BaPrO3 is a paramagnetic material with electron conduction in semiconducting region [5].…”

“…This material occurs the magnetic transition from paramagnetic phase to antiferromagnetic phase [6][7][8][9][10]. The structural and magnetic properties have been investigated in the research area of solid state physics [1][2][3][4][5][6][7][8][9][10]. In the research area of electrochemical, it is known that BaPrO3 exhibits high electron-proton mixed conduction in intermediate temperature region (600~300°C) when Yb 3+ ions are substituted into Pr 4+ site [11][12][13][14].…”