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Phase Relations in the ZrO2-Y2O3-La2O3 System at 1250 °C

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Abstract:

Phase equilibria in the ternary system ZrO2-Y2O3-La2O3 at 1250 °C have been studied and isothermal section have been developed. Fine chemical technique such as co-precipitation was used to obtain ceramic nanopowders (with average particle size of 8-20 nm) available for nonisothermal sintering as well. The phase compositions of the annealed samples were studied by methods of X-ray analysis at 20 °C, petrographic and electron microprobe X-ray analyses. No ternary compounds were found. The phase equilibria in the system are determined by intermediate phases: La2Zr2O7 and LaYO3 that crystallize in the pyrochlore and perovskite-type structures, respectively. Solid solutions based on the constituent oxides such as tetragonal (T) and cubic fluorite-type structure (F) ZrO2, cubic form of rare-earth oxides (C-type) Y2O3,as well as hexagonal (A) and monoclinic (B) forms La2O3 were found at 1250 °C. The nanocrystalline powders of tetragonal zirconia actively sintered on heating up to 1150-1400 °C and the powders of lanthanum zirconate show active densification on heating up to 1550-1650 °C. The electrical properties (at 600-950 °C) of yttria-doped pyrochlore were measured, the highest conductivity has been revealed at 10 mol % Y2O3.

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Periodical:

Materials Science Forum (Volume 518)

Pages:

343-348

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.518.343

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Online since:

July 2006

Authors:

E.R. Andrievskaya, V.P. Red'ko

Keywords:

Fluorite, Fuel Cell (FC), Functional Material, Ion Conductor, Isothermal Section, Lanthana, Phase Diagram, Phase Equilibria, Pyrochlore, Solid Solution, Thermal Barrier Coating (TBC), Yttria, Zirconia

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© 2006 Trans Tech Publications Ltd. All Rights Reserved

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