Fracture properties of polycrystalline YBa sub 2 Cu sub 3 O sub x

Conference · Wed Jul 01 04:00:00 EDT 1987 · Advanced Ceramic Materials; (USA)

OSTI ID:5123915

Cook, R F; Shaw, T M; Duncombe, P R ^[1]

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1. IBM Thomas J. Watson Research Center, Yorktwon Heights, NY (USA)

Polycrystalline YBa{sub 2}Cu{sub 3}O{sub x} has been prepared by sintering pre-reacted powder in oxygen to yield a material with 15 {mu}m grain size, 86% relative density and which superconducts above liquid nitrogen temperatures. Indentation crack length measurements give a toughness K{sub c} = 1.3 {plus minus} 0.2 MPa m{sup {1/2}}, above a threshold contact load for radial crack initiation of approximately 5 N (compared with 1.1 MPa m{sup {1/2}} and < 0.1 N, respectively, for single crystals). The increased toughness and threshold contact load are controlled by the deviation of cracks from the plane of maximum driving force for fracture by weak grain boundaries and preferred fracture planes within grains. Optical microscopy of indentation cracks and scanning electron microscopy of fracture surfaces reveals approximately 50% intergranular fracture. The hardness of the polycrystal was H = 2.0 {plus minus} 0.5 GPa (compared with 8.7 GPa for single crystals). The decreased hardness arises from the porosity of the polycrystalline material and grain boundary sliding under the indentation contact. Time dependent growth of lateral cracks at the indentation contacts suggests that these materials are susceptible to moisture controlled non-equilibrium crack growth.

• OSTI ID: 5123915
• Report Number(s): CONF-8704372--
• Conference Information: Journal Name: Advanced Ceramic Materials; (USA) Journal Volume: 2:3B
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
&amp; Refractories-- Mechanical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CERAMICS
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRACK PROPAGATION
CRACKS
CRYSTAL STRUCTURE
CRYSTALS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
FABRICATION
FRACTURE PROPERTIES
GRAIN BOUNDARIES
HARDNESS
MECHANICAL PROPERTIES
MICROSCOPY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POLYCRYSTALS
POROSITY
POWDERS
SINTERING
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TIME DEPENDENCE
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES