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Synthesis and characterization of lanthanum aluminate powders via a polymer complexing plus combustion route
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.ORCID iD: 0000-0003-3060-9987
2012 (English)In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 132, no 2-3, 309-315 p.Article in journal (Refereed) Published
Abstract [en]

Lanthanum aluminate powders were prepared by a simple polymer complexing plus combustion method using PVA or PEG as complexing agent and fuel. The influence of different polymers on phase purity, powder morphology and sintering performance were investigated. Trace amount impurity La 23 exists in the PEG powder, but it could be eliminated after high temperature sintering. The pure phase LaAlO 3 can be easily obtained in PVA powders calcined at 950 °C even severe aggregation always exists. PEG shows advantages over PVA in terms of the densification and microstructure control during sintering process. The high relative density of 97.0% and homogeneous fine microstructure with grain size < 3 μm can be obtained in the PEG-derived sample sintered at 1600 °C for 5 h. To obtain better quality LaAlO 3 powders through combustion route, PEG is preferred over PVA.

Place, publisher, year, edition, pages
2012. Vol. 132, no 2-3, 309-315 p.
Keyword [en]
anthanum aluminate, PEG, Perovskite, PVA
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-14241DOI: 10.1016/j.matchemphys.2011.11.019ISI: 000301083800013Scopus ID: 2-s2.0-84856596512OAI: oai:DiVA.org:kth-14241DiVA: diva2:331851
Note
QC 20120327. Updated from submitted to published. Previous title: "Synthesis and characterisation of lanthanum aluminate powders via a polymer complexing plus combustion route" (obs, s -> z i characterisation)Available from: 2010-07-27 Created: 2010-07-27 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Preparation and characterization of perovskite structure lanthanum gallate and lanthanum aluminate based oxides
Open this publication in new window or tab >>Preparation and characterization of perovskite structure lanthanum gallate and lanthanum aluminate based oxides
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present work was initiated to study the synthesis and properties of lanthanum gallate based oxides as intermediate temperature electrolyte for solid oxide fuel cells. The wet chemical method, polymer complexing route, was used to prepare the precursor powders. To further investigate the polymer complexing method, it was also applied to the preparation of lanthanum aluminate based oxides.

 

Single perovskite phase La0.8Sr0.2Ga0.83Mg0.17O2.815 can be prepared by the polymer complexing method using PVA as complexing agent. The thermal decomposition of the precursor powder undergoes three stages. While complete decomposition of the precursor is obtained at 1000°C. Further investigation of LaGaO3 doped with various amounts Sr or/and Mg was conducted. Three secondary phases were identified by X-ray diffraction, e.g. LaSrGaO4, LaSrGa3O7 and La4Ga2O9. The relative amount of these secondary phases depends on the doping compositions. Sr doping produced more Sr rich secondary phases with increasing content, while enhanced solid solubility was observed with Mg addition. Sintered samples showed dense microstructures with well-developed equiaxed grains, and the secondary phases were mainly in the grain boundaries. The oxygen ionic conductivity was enhanced by doping with Sr and Mg. Mg doping showed the increased activation energy of conductivity.

 

Preliminary study showed that the lanthanum gallate and ceria composite electrolyte is mainly fluorite CeO2 phase after sintering. The minority secondary phase, Sm3Ga5O12, was also detected by XRD. The composite electrolyte showed superior electrical performance. It exhibited the highest conductivity in the temperature range of 250–600°C, compared with lanthanum gallate and ceria specimens.

 

The phase pure perovskite La0.9Sr0.1Al0.85Mg0.1Co0.05O2.875 powders can easily be obtained by the polymer method using PVA as complexing agent. No secondary phase was detected after calcination at various temperatures (500–1100°C). The fully crystallized LaAlO3 phase was prepared after calcination at 900°C. Meanwhile the secondary phases were difficult to eliminate in the Sr- and Mg- doped LaGaO3 powder prepared by the same polymer method. It is thus concluded that the polymer, PVA in this work, provides more homogeneous mixing for cations of lanthanum aluminate based oxides, compared with the one for doped lanthanum gallate.

 

The influence of different complexing agents, e.g. PVA and PEG, was investigated in the synthesis of lanthanum aluminate powders. Minority impurity La2O3 existed in the PEG powder, but it could be eliminated after sintering at high temperatures. Although the pure phase LaAlO3 can be easily obtained in PVA powders calcined at 950°C, more seriously aggregated particles existed. PEG showed advantages over PVA in terms of better densification and microstructure control in the sintered products. To select proper polymers in complex oxide synthesis, the agglomeration and morphology of the powder are the most important factors to be considered.

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. viii, 38 p.
Keyword
Lanthanum gallate, lanthanum aluminate, ceria, composite, solid oxide fuel cell, electrolyte, polymer complexing.
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-10588 (URN)978-91-7415-324-8 (ISBN)
Public defence
2009-06-12, B2, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100727Available from: 2009-06-04 Created: 2009-05-29 Last updated: 2010-07-27Bibliographically approved

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