Novel processing route of La9.33Si2Ge4O26
electrolytes for SOFCs combining
mechanical alloying and microwave hybrid
B. Trindade 1 , A. Cavaleiro 1, C. Alves2, F.A.C. Oliveira2 , T. Marcelo2, J.
1 CEMUC, Mechanical Engineering Department, University of Coimbra
2 Laboratório Nacional de Energia e Geologia I.P., Lisboa
1Materiais 2013, Coimbra, Portugal, March 25 – 27, 2013
Advantages over traditional energy conversion systems:
cleaner and more efficient
Fuel cell is a device that generates electricity by a chemical reaction.
Yttria-stabilised zirconia (YSZ)
The requirements for the electrolyte are:
• high ionic conductivity
• very low electronic conductivity
• high hardness
• chemical stability
• thermal expansion coefficient compatibly
with the other parts of the cell
The ionic conductivity varies strongly
with the sintering conditions
Different sintering conditions will
result in diverse microstructure
Microstructure with full density and
suitable grain size are essential for a
high-performance ionic conductor
Density and open porosity
Density (g.cm-3) Open Porosity (%)
Theoretical density value of La9.33Si2Ge4O265.446 g.cm-3
The grain size of MW
sample is about 1.9 m
Thermal Expansion Coefficient:
Values similar to the ones of yttria-stabilized zirconia electrolytes normally used in SOFCs.
• Oxyapatite-based La9.33Si2Ge4O26 samples for SOFC electrolytes have
been prepared by conventional and microwave hybrid sintering at 1350ºC
(250ºC lower than conventional processes)
• Quite dense samples were obtained independently of the sintering
process. Almost full dense sample was obtained by MW powders with
promising mechanical properties.
• The ionic conductivity values of sintered samples did not show any
relevant dependence on the different production parameters.
• Microwave hybrid sintering is a novel suitable process for the
densification of La9.33Si2Ge4O26 powders.