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Synthesis of La0.9Sr0.1Al0.85Mg0.1Co0.05O2.875 using a polymeric method
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.
2009 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, ISSN 0955-2219, Vol. 29, no 6, 1133-1138 p.Article in journal (Refereed) Published
Abstract [en]

Nanocrystalline La0.9Sr0.1Al0.85Mg0.1Co0.05O2.875 (LSAMC) powders were synthesized via a polymeric method using poly(vinyl alcohol) (PVA). The effect of PVA content on the synthesized powders was studied. When the ratio of positively charged valences (Mn+) to hydroxyl groups (-OH) is 1.5:1, crystalline LaAlO3 could be obtained at such a low calcination temperature as 700 degrees C. While at 900 degrees C the ratio is of less importance, since pure LaAlO3 perovskite could be formed for all powders after calcination at 900 degrees C. Thermal analysis (TG/DTA) was utilized to characterize the thermal decomposition behaviour of precursor powders. The chemical structure of the calcined powder was studied by Fourier transform infrared (FTIR) spectroscopy. The powder morphology and microstructure were examined by SEM. Dense pellets with well-developed submicron microstructures could be formed after sintering at 1450 degrees C for 5 h. Compared with the solid-state reaction method, the sintering temperature is substantially lower for powder prepared by the PVA method. This is due to the ultrafine and highly reactive powder produced.

Place, publisher, year, edition, pages
2009. Vol. 29, no 6, 1133-1138 p.
Keyword [en]
Nanocrystalline, Lanthanum aluminate, Perovskite, Polymeric method
National Category
Materials Engineering
URN: urn:nbn:se:kth:diva-14240DOI: 10.1016/j.jeurceramsoc.2008.08.007ISI: 000264385000018ScopusID: 2-s2.0-60649113648OAI: diva2:331849

QC 20100727

Available from: 2010-07-27 Created: 2010-07-27 Last updated: 2014-04-09Bibliographically 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.
Lanthanum gallate, lanthanum aluminate, ceria, composite, solid oxide fuel cell, electrolyte, polymer complexing.
National Category
Other Materials Engineering
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)
QC 20100727Available from: 2009-06-04 Created: 2009-05-29 Last updated: 2010-07-27Bibliographically approved

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