Orientation of ceramic microstructures by hot-forming methods. [Bi/sub 2/WO/sub 6/, Bi/sub 2/MoO/sub 6/, PbBi/sub 2/Nb/sub 2/O/sub 9/, Bi/sub 4/Ti/sub 3/O/sub 12/]

Technical Report · Fri Jan 01 04:00:00 EST 1982

OSTI ID:6578900

Knickerbocker, J U

Powders of layered-structure compounds Bi/sub 2/WO/sub 6/, Bi/sub 2/MoO/sub 6/, PbBi/sub 2/Nb/sub 2/O/sub 9/ and Bi/sub 4/Ti/sub 3/O/sub 12/ were prepared by solid-state calcination and salt synthesis. Powders were fabricated into dense ceramics by hot-pressing, hot-forging, and hot-extrusion. Microstructures showed little grain orientation in hot-pressed samples. However, hot-forged samples had microstructures with up to 99% grain orientation, and hot-extruded samples had up to 92% grain alignment. Greater grain sizes were observed for hot-forged and hot-extruded microstructures than for hot-pressed. Anisotropy of dielectric constant, tangent par. delta, ac conductivity, dc resistivity, ferroelectric and piezoelecric properties were measured. Significant dielectric anisotropy occurred for hot-forged Bi/sub 2/MoO/sub 6/, PbBi/sub 2/Nb/sub 2/O/sub 9/ and Bi/sub 4/Ti/sub 3/O/sub 12/, with pseudo single-crystal values for PbBi/sub 2/Nb/sub 2/O/sub 9/ and Bi/sub 4/Ti/sub 3/O/sub 12/. Salt synthesized powders were electrically aligned by dielectrophoretic poling prior to hot-forging, and the degree of three dimensional grain orientation was determined. Dielectric constants were in good agreement with single crystal data and values calculated from dielectric mixing rules. The best powders for dense grain-oriented microstructures had small grain sizes for sintering activity, had large aspect ratios for mechanical grain alignment, and were deagglomerated for dielectrophoretic alignment. Thoroughly washed salt synthesized powders were required for dielectrophoretic poling experiments. Hot-forging produced the greatest combination of grain orientation and fired densities.

• Research Organization: Illinois Univ., Urbana (USA). Dept. of Ceramic Engineering
• DOE Contract Number: AC02-76ER01198
• OSTI ID: 6578900
• Report Number(s): DOE/ER/01198-1396; ON: DE83005232
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
ANISOTROPY
BISMUTH COMPOUNDS
BISMUTH TUNGSTATES
CRYSTAL STRUCTURE
CRYSTALS
DIELECTRIC PROPERTIES
ELECTRICAL PROPERTIES
EXTRUSION
FABRICATION
FERROELECTRIC MATERIALS
FORGING
GRAIN ORIENTATION
GRAIN SIZE
HOT PRESSING
LAYERS
LEAD COMPOUNDS
MATERIALS WORKING
MICROSTRUCTURE
MOLYBDATES
MOLYBDENUM COMPOUNDS
NIOBATES
NIOBIUM COMPOUNDS
ORIENTATION
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POLYCRYSTALS
PRESSING
SIZE
TITANATES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TUNGSTATES