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Analytical Microscopy Study of Phases and Fracture in Y 2 O 3 ‐La 2 O 3 Alloys
Author(s) -
WEI GEORGE C.,
EMMA T.,
RHODES WILLIAM H.,
HORVATH STEVEN,
HARMER MARTIN
Publication year - 1988
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1988.tb07529.x
Subject(s) - materials science , monoclinic crystal system , equiaxed crystals , phase (matter) , transmission electron microscopy , phase diagram , crystallography , analytical chemistry (journal) , sintering , r phase , mineralogy , microstructure , composite material , crystal structure , chemistry , nanotechnology , martensite , organic chemistry , chromatography
Transmission electron microscopic analyses defined the structures and compositions in single‐phase and two‐phase La 2 O 3 ‐doped Y 2 O 3 materials fabricated by the transient solid second‐phase sintering. The composition in single‐phase, 10‐mol%‐La 2 O 3 ‐doped, sintered and annealed samples was found to be uniform, indicating that diffusivity was sufficiently high for homogenization in the single‐phase field. Two‐phase, 16‐mol%‐La 2 O 3 ‐doped, sintered and annealed samples showed two morphologies: (1) intragranular, lath‐like, monoclinic second‐phase particles (twinned and untwinned) and (2) equiaxed cubic matrix. The second‐phase particles were identified as the monoclinic phase derived from the high‐temperature hexagonal phase through a rapid phase transition. A short, high‐temperature anneal (2200°C for 1 min) of 9 mol% La 2 O 3 ‐Y 2 O 3 composition was found to retain the hexagonal phase. Microchemical analyses of the phases suggested adjustments to the Y 2 O 3 ‐La 2 O 3 phase diagram. Observation of the interactions of the intragranular second‐phase particles with crack propagation indicated crack deflection as one of the mechanisms responsible for toughening (1.5 vs 0.9 MPa · m 1/2 ).