Anomalous polarization switching and permanent retention in a ferroelectric ionic conductor

To lower operating temperatures of solid oxide fuel cells (SOFCs), the development of ion-conducting oxides with high conductivity and durability is desired. In this work, we investigated Zr-substituted “Ba3Y4O9” as an ionic conductor at intermediate temperatures and found that the Zr substitution for Y dramatically improves the phase stability in humidified atmospheres at 300-800 °C. The total electrical conductivity of 20 mol% Zr-substituted Ba3Y4O9 is about 1 mS/cm at 700 °C in dry H2 and O2 atmospheres and the contribution of electronic conduction (both hole and electron) is relatively small compared with Y-doped BaZrO3 (BZY) and Gd-doped CeO2 (GDC) which are typical intermediate-temperature ionic conductors. Besides, in the Zr-substituted “Ba3Y4O9” samples, we observed that BaO-rich amorphous phase coexists with the main phase whose composition is estimated to be Ba:(Y+Zr) ~ 2:3. Therefore, the main conducting phase might be Ba-deficient Ba3Y4O9. The mechanism of the ionic conduction and the improvement of chemical stability has not been revealed yet due to the lack of crystallographic information about the Ba-deficient phase. While we are now working on further investigation, we promptly report the characteristic of the new compound.

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New Good Ionic Conductor: Ba-Deficient Ba3Y4O9 with Zr Substitution

10.26434/chemrxiv.13385228 ◽

2020 ◽

Author(s):

Katsuhiro Ueno ◽

Naoyuki Hatada ◽

Tetsuya Uda

Keyword(s):

Solid Oxide Fuel Cells ◽

Ionic Conduction ◽

Ionic Conductor ◽

Electronic Conduction ◽

Ionic Conductors ◽

Conducting Phase ◽

Conducting Oxides ◽

Total Electrical Conductivity ◽

Ion Conducting ◽

New Good

To lower operating temperatures of solid oxide fuel cells (SOFCs), the development of ion-conducting oxides with high conductivity and durability is desired. In this work, we investigated Zr-substituted “Ba3Y4O9” as an ionic conductor at intermediate temperatures and found that the Zr substitution for Y dramatically improves the phase stability in humidified atmospheres at 300-800 °C. The total electrical conductivity of 20 mol% Zr-substituted Ba3Y4O9 is about 1 mS/cm at 700 °C in dry H2 and O2 atmospheres and the contribution of electronic conduction (both hole and electron) is relatively small compared with Y-doped BaZrO3 (BZY) and Gd-doped CeO2 (GDC) which are typical intermediate-temperature ionic conductors. Besides, in the Zr-substituted “Ba3Y4O9” samples, we observed that BaO-rich amorphous phase coexists with the main phase whose composition is estimated to be Ba:(Y+Zr) ~ 2:3. Therefore, the main conducting phase might be Ba-deficient Ba3Y4O9. The mechanism of the ionic conduction and the improvement of chemical stability has not been revealed yet due to the lack of crystallographic information about the Ba-deficient phase. While we are now working on further investigation, we promptly report the characteristic of the new compound.

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IONIC CONDUCTION AND ELECTRONIC CONOLUCTION IN THE HIGH IONIC CONDUCTOR OF THE SYSTEM Bi2O3-Y2O3

Acta Physica Sinica ◽

10.7498/aps.33.221 ◽

1984 ◽

Vol 33 (2) ◽

pp. 221

Author(s):

WANG CHANG-ZHEN ◽

XU XIU-GUANG

Keyword(s):

Ionic Conduction ◽

Ionic Conductor

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Stress-Induced Ordering in Y203-Stabilized Tetragonal Zr02

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118035 ◽

1985 ◽

Vol 43 ◽

pp. 222-223

Author(s):

J. Y. Koo ◽

M. P. Anderson

Keyword(s):

Electron Diffraction ◽

Ionic Conduction ◽

Electron Diffraction Study ◽

Ceramic Materials ◽

Bright Field Image ◽

Transformation Toughening ◽

Ion Milling ◽

Thin Foils ◽

Carbon Coated ◽

Convergent Beam

Tetragonal Zr02 has been used as a toughening phase in a large number of ceramic materials. In this system, complex diffraction phenomena have been observed and an understanding of the origin of the diffraction effects provides important information on the nature of transformation toughening, ionic conduction, and phase destabilization. This paper describes the results of an electron diffraction study of Y203-stabilized, tetragonal Zr02 polycrystals (Y-TZP).Thin foils from the bulk Y-TZP sample were prepared by careful grinding and cryo ion-milling. They were carbon coated and examined in a Philips 400T/FEG microscope. Fig. 1 shows a typical bright field image of the 100% tetragonal(t) Zr02. The tetragonal structure was identified by both bulk x-ray diffraction and convergent beam electron diffraction (Fig. 2. A local region within a t-Zr02 grain was subjected to an intense electron beam irradiation which caused partial martensitic transformation of the t-Zr02 to monoclinic(m) symmetry, Fig. 3 A.

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A transmission electron microscopic study of structural transitions in fast ionic conductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125713 ◽

1987 ◽

Vol 45 ◽

pp. 156-157

Author(s):

R. B. Queenan ◽

P. K. Davies

Keyword(s):

Optical Properties ◽

Ionic Conduction ◽

Recent Observation ◽

Ionic Conductivities ◽

Sodium Aluminate ◽

Two Dimensions ◽

Ionic Conductors ◽

Electron Microscopic ◽

Transmission Electron ◽

Trivalent Cations

Na ß“-alumina (Na1.67Mg67Al10.33O17) is a non-stoichiometric sodium aluminate which exhibits fast ionic conduction of the Na+ ions in two dimensions. The Na+ ions can be exchanged with a variety of mono-, di-, and trivalent cations. The resulting exchanged materials also show high ionic conductivities.Considerable interest in the Na+-Nd3+-ß“-aluminas has been generated as a result of the recent observation of lasing in the pulsed and cw modes. A recent TEM investigation on a 100% exchanged Nd ß“-alumina sample found evidence for the intergrowth of two different structure types. Microdiffraction revealed an ordered phase coexisting with an apparently disordered phase, in which the cations are completely randomized in two dimensions. If an order-disorder transition is present then the cooling rates would be expected to affect the microstructures of these materials which may in turn affect the optical properties. The purpose of this work was to investigate the affect of thermal treatments upon the micro-structural and optical properties of these materials.

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