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Yttrium doped hafnium oxide Hf0.69Y0.31O2-δ used for solid oxide fuel cell electrolytes and electronic materials
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.ORCID iD: 0000-0001-5258-099X
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.ORCID iD: 0000-0003-3060-9987
(English)Manuscript (preprint) (Other academic)
Abstract [en]

An Yttrium doped hafnium oxide Hf0.69Y0.31O2-δ (YSH orYDH) is obtained by a modified solid state reactionmethod, where freeze drying is implemented to reduce theagglomeration. Refinement result shows that YSH is influorite cubic crystal with lattice parameter a = b = c =5.140674 Å (Figure 1). Based on this, the ionic radius ofY3+ in YSH for 8 coordination is 0.1006 nm, confirms theprevious prediction that it should be smaller than 0.1015nm. The YSH ceramic material with relative density of>97.5% can be obtained by conventional sintering at 1650℃ for 10hrs. Its conductivity is only 3.65×10-5 s cm-1 at700 ℃ (Figure 2), which is too low for solid oxide fuelcell application. However, its high dielectric constant22.03 (Figure 3a, average value, which is 1.4 times largerthan the pure Hafnia) and low dielectric loss over a widefrequency range and DC potential make it very promisingfor the microelectronic device application.

National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-146190OAI: oai:DiVA.org:kth-146190DiVA: diva2:722678
Note

QS 2014

Available from: 2014-06-09 Created: 2014-06-09 Last updated: 2014-06-09Bibliographically approved
In thesis
1. Exploratory Study of Novel Materials Used for Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) Electrolytes
Open this publication in new window or tab >>Exploratory Study of Novel Materials Used for Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) Electrolytes
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Currently, yttria-stabilized zirconia (YSZ) is still the dominant electrolyte material in commercial SOFC applications. But it has severe drawbacks due to its high operating temperatures. In present work, two electrolyte materials: Hf0.69Y0.31O2-δ (YSH) used as oxygen ion conductor and BaZr0.5Ce0.3Ln0.2O3-δ (BZCLn532, Ln=Y, Sm, Gd, Dy) used as protonic conductors were studied at intermediate temperatures (IT, 500-700 ℃). The work is focused on the following parts:

1)      A pure and well-crystallized YSH powder was successfully synthesized by using a modified solid state reaction method. The obtained YSH is in a fluorite cubic structure with a lattice parameter 5.140674 Å from the Rietveld refinement analysis. A YSH ceramic material with a relative density of 97.5% is obtained by a conventional sintering at a temperature of 1650 ℃. The oxygen ion conductivity of the YSH ceramic is 3.65×10-5 S cm-1 at a temperature of 700 ℃, which is too low for oxygen ion conductor applications. In contrast, there is an obvious enhancement of the protonic conductivity, when the testing temperature is higher than 600 ℃. The conductivity that tested in a moist atmosphere at a temperature of 700 ℃ is 5.19×10-5 S cm-1, which is 1.4 times higher than the oxygen ion conductivity.

2)      BaZr0.5Ce0.3Ln0.2O3-δ (BZCLn532, Ln=Y, Sm, Gd, Dy) based electrolytes were successfully synthesized by using a cost-effective solid state reactive sintering (SSRS) method with 1 wt.% NiO as a sintering aid. Based on the obtained conductivities of BZCLn532 compounds measured in a dry air atmosphere and a moist air atmosphere, BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) and BaZr0.5Ce0.3Dy0.2O3-δ (BZCD532) compounds are demonstrated to be good candidates for both oxygen ion conductor and proton conductor materials for solid oxide fuel cells operating at intermediate temperatures.

In summary, proton conducting ceramic materials represent one type of promising materials for future IT-SOFCs electrolyte applications.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. vi, 34 p.
Keyword
Hafnium oxide; Solid oxide fuel cells (SOFCs); Electrolyte; Electrochemical impedance spectroscopy; Solid state reaction method; Solid state reactive sintering (SSRS); Ionic conductivity; oxygen ion conductivity; Protonic conductivity; Composite electrolyte.
National Category
Ceramics
Identifiers
urn:nbn:se:kth:diva-145211 (URN)978-91-7595-132-4 (ISBN)
Presentation
2014-06-05, Konferensrummet (N111), Brinellvägen 23, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20140609

Available from: 2014-06-09 Created: 2014-05-14 Last updated: 2014-06-09Bibliographically approved

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Bu, JunfuZhao, Zhe

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