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Sinterable and strengthened magnesium oxide ceramic materials
| Details |
Inventors: Virkar, Anil; Yuan, Thomas C.;
Assignee: The Dow Chemical Company (Midland, MI)
Primary Examiner: Lechert, Jr.; Stephen J.
Assistant Examiner:
Attorney, Agent or Firm: Trask, Britt & Rossa
Magnesium oxide ceramic bodies may be strengthened by inclusion of zirconium oxide particles, and may be further sintered to a density approaching theoretical density by conventional sintering techniques by inclusion of sintering aids, such as manganese oxide and iron oxide. |
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DETAILED DESCRIPTION The instant invention comprises magnesium oxide ceramic bodies which contain a sintering aid of a metallic oxide wherein the metal portion of the oxide has an ionic radius substantially similar to magnesium, and has valence states greater than +2, and especially valence states of +3, +4 or more.
Particular sintering aids found effective in the invention are manganese oxide, iron oxide, and the like.
Such sintering aids have been found effective when included in very minor amounts, that is, usually less than about 5% by weight of sintering aid based upon the weight of magnesium oxide present.
Particularly good results have been achieved when the sintering aid has been present at less than about 2% by weight.
Also, the invention comprises magnesium oxide bodies incorporating zirconium oxide, hafnium oxide, or the like, which act to toughen the magnesium oxide body.
Zirconium oxide or hafnium oxide is generally present in an amount less than 50% by volume of the magnesium oxide present in the ceramic body, and generally less than about 40% by volume, and particularly less than about 30% by volume.
Zirconia- or hafnia-toughened magnesium oxide ceramic bodies may be prepared by pressurized sintering, that is, hot-pressing or hot isostatic pressing, or by conventional sintering by the inclusion of an appropriate sintering aid of the type identified herein.
A sintered ceramic body of this invention comprises magnesium oxide and a very minor amount of a metal oxide having the formula AO.
sub.
x wherein A is a metal which has a valence state greater than +2 and has an ionic radius substantially similar to a magnesium ion and x is a number having a value greater than one-half the valence state of A.
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