High temperature creep of an orthorhombic perovskite-YAlO3

Details High temperature creep of an orthorhombic perovskite-YAlO3 High temperature creep of an orthorhombic perovskite-YAlO3

Jan 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999pepi..110...51w&link_type=abstract

Physics of the Earth and Planetary Interiors, Volume 110, Issue 1-2, p. 51-69.

Physics

7

Scientific paper

Compression tests were performed on single crystals of orthorhombic perovskite (YAlO3) along the [110] and [100] directions at temperature of T=1763-1883 K (0.82-0.88 Tm) and Ptotal=0.1 MPa in a controlled atmosphere of fO2=10-17-0.02 MPa. Applied stresses were in the range of 70-300 MPa yielding strain rates of /ɛ˙~10-7 s-1 to ~10-4 s-1. Creep strength of YAlO3 is significantly higher than those of cubic perovskites when compared at same normalized conditions. Creep behaviour of YAlO3 depends on crystallographic orientation and oxygen fugacity and can be summarized as (/ɛ˙ (s-1), σ (MPa), fO2 (MPa), R (kJ (mol K)-1) and T (K)): (1) for [110] orientation:ɛ˙=(4.4+/-1.7).1013σ3.0+/- 0.2f0.00+/- 0.05O2expfO2>10-7.0 MPaandɛ˙=(3.0+/-1.6)×10-4σ3.3+/- 0.2f-0.22+/- 0.02O2expfO2<10-7.0 MPa(2) for [100] orientation:ɛ˙=(2.4+/- 0.7)×1011σ2.8+/-0.2f0.00+/- 0.05O2expDislocation microstructures of deformed YAlO3 show marked difference from those of cubic perovskites. Importance of dislocation climb and splitting (dissociation) is demonstrated by TEM observations. These observations indicate that the deformation mechanisms in this orthorhombic perovskite is fundamentally different from those in cubic perovskites and therefore the results for cubic perovskites may not be applied to the Earth's lower mantle where orthorhombic perovskite is considered to be the dominant phase.

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