Chapter 7. Sources of Sintering Inhibition in Tape-Cast Aluminas

  1. John B. Wachtman Jr.
  1. Mikio Geho1 and
  2. Hayne Palmour III2

Published Online: 26 MAR 2008

DOI: 10.1002/9780470314272.ch7

A Collection of Papers on Engineering Aspects of Fabrication of Ceramics: Ceramic Engineering and Science Proceedings, Volume 14, Issue 11/12

A Collection of Papers on Engineering Aspects of Fabrication of Ceramics: Ceramic Engineering and Science Proceedings, Volume 14, Issue 11/12

How to Cite

Geho, M. and Palmour, H. (1993) Sources of Sintering Inhibition in Tape-Cast Aluminas, in A Collection of Papers on Engineering Aspects of Fabrication of Ceramics: Ceramic Engineering and Science Proceedings, Volume 14, Issue 11/12 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314272.ch7

Author Information

  1. 1

    R & D Labs Center Kanebo, Ltd. Osaka 534 Japan

  2. 2

    Sintering Research Laboratory, Department of Materials Science & Engineering, North Carolina State University, Raleigh, NC 27695-7907

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1993

ISBN Information

Print ISBN: 9780470375280

Online ISBN: 9780470314272

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Keywords:

  • dilatometric;
  • perpendicular;
  • deflocculant;
  • alumina;
  • rheological

Summary

High-purity, lightly MgO-doped A12O3 tapes (20–200 m̈m thick) were tape cast from water- or MEK-EtOH-based slurries. Dilatometric data obtained in directions both parallel and perpendicular to the cast plane under constant-rate-of-heating conditions (5°C/min to 1600°C) were utilized to evaluate all aspects of densification behavior during sintering, including small but significant tapethickness dependencies and orientation-anisotropy effects. Importantly, two unreported types of sintering inhibition were found: one is attributed to excess amounts of organic additives (>10 wt%) in the water-based slurries; the other is associated with a phosphate-containing deflocculant used in the organic-solvent slurries. In aqueous systems, overuse of organic binders/plasticizers leads to excessive dilatation (shrinkage or expansion) at low temperatures (∼350°–500°C), thereby degrading particle-particle contacts and thus inhibiting sintering in early-intermediate stages of densification. In these aqueous-system experiments, total organic content could be reduced to as low as 6.5 wt%, yielding good tape quality and improved sintering behavior. In the organic solvent system, P2O5 from the deflocculant appears to react with Al2O3 and MgO; initially it forms liquid phases, but thereafter yields binary and/or ternary crystalline phases that inhibit late-stage sintering.