Hydrogen in perovskites: Mechanism of solubility, chemical state, effect on electron subsystem, phase transformation

Abstract

Abstract. The phenomena of hydrogen/water solubility in YBa2Cu307_ 5 and BaCeO 3 undoped and doped by Y and Nd are considered. New experimental data as well as recently published data have been accumulated to discuss the chemical state of protons, taking into account the fairly strong interaction of the protons with the electron subsystem. Phase transformation of the studied oxides induced by hydrogen/water intercalation were revealed by the investigations of thermal effects, Xray diffraction, Raman spectroscopy, inelastic neutron scattering and nuclear quadrupole resonance.

Advanced materials for SOFC application: Strategies for the development of highly conductive and stable solid oxide proton electrolytes

“…Formally t = 1, corresponds to the cubic structure, and its deviations from unity upward and downward denotes the formation of orthorhombic, rhombohedral and hexagonal perovskite structures, which, as a rule, are characterized by low stability than cubic one [18,19]. The calculation showed that t factor of nominally pure barium cerate is equal 0.938, and at room temperature it has an orthorhombic perovskite structure [20][21][22]. In the case of co-doped systems, such as for example BaCe 1-x-y Nb x Y y O 3- …”

Well-known perovskites (cerates, cuprates, manganates): Problems and facts; A review of nontraditional approaches

“…However, this phenomenon is not known in the case of strong dielectric materials, like barium cerate (energy gap near 4 eV). Nevertheless, the necessity of considering the mixedvalence state of cerium in barium cerate and maybe strontium has come up in the course of the investigations of nominally undoped BaCeO3 [3,7,[10][11][12][13][14]. In spite of the strong conclusion of the widely assumed acid-base concept on hydrogen intercalation into cerates doped by trivalent ions, protons have been revealed in nominally undoped cerates and titanates of alkaline earths [7,14].…”

“…together with Ph. Colomban et al he has estimated the monoatomic state of protons in hydrides of transition metals [3]. Recently, experiments of studying simultaneously the mobility of oxygen and hydrogen were performed.…”

Structural stability of anhydrous proton conducting SrZr0.9Er0.1O3−δ perovskite ceramic vs. protonation/deprotonation cycling: Neutron diffraction and Raman studies

“…the determination of an exact bulk proton nature, should be established [25][26][27][28][29][30]. The question if the Proton is a Guest or a Host in an anhydrous oxide has been addressed by Y. Baikov [31]. The nature of chemical bonds between the proton and a perovskite framework (hydroxyl ion, free, ionic proton …) remains debated [7,28,29,[31][32][33]).…”