State of Oregon

John S Evans

Arthur W Sleight

Mary A Thundathil

Low or negative thermal expansion compounds are described having a formula of A.sub.2-x.sup.3+ A.sub.y.sup.4+ M.sub.z.sup.3+ M.sub.3-y.sup.6+ P.sub.y O.sub.12. It currently is believed that y can vary from about 0 to about 2, x equals the sum of y and z and varies from about 0.1 to about 1.9. Without limitation, novel compounds satisfying the formula A.sub.2-x.sup.3+ A.sub.y.sup.4+ M.sub.z.sup.3+ M.sub.3-y.sup.6+ P.sub.y O.sub.12 where y=0 may be selected from the group consisting of Al.sub.1.5 In.sub.0.5 W.sub.3 O.sub.12, Al.sub.1.6 In.sub.0.4 W.sub.3 O.sub.12, Al.sub.1.7 In.sub.0.3 W.sub.3 O.sub.12, Al.sub.1.8 In.sub.0.2 W.sub.3 O.sub.12, YAlW.sub.3 O.sub.12, ScAlW.sub.3 O.sub.12, ScGaW.sub.3 O.sub.12, ScInW.sub.3 O.sub.12, ScHoW.sub.3 O.sub.12, ScYbMo.sub.3 O.sub.12 and ErInW.sub.3 O.sub.12. Without limitation, novel compounds satisfying the formula A.sub.2-x.sup.3+ A.sub.y.sup.4+ M.sub.z.sup.3+ M.sub.3-y.sup.6+ P.sub.y O.sub.12 where y=2 may be selected from the group consisting of Hf.sub.2 WP.sub.2 O.sub.12 and Hf.sub.2 MoP.sub.2 O.sub.12. The present invention also provides compositions useful for decreasing the positive thermal expansion of a material or materials included in the compositions. The compositions comprise at least a first material and a second material where the first material has low or negative thermal expansion properties and the second material exhibits positive thermal expansion. Novel compositions and methods for making and using such compositions can be made using a first material selected, without limitation, from the group consisting of Al.sub.2 W.sub.3 O.sub.12, Al.sub.2 Mo.sub.3 O.sub.12, In.sub.2 W.sub.3 O.sub.12, Al.sub.1.5 In.sub.0.5 W.sub.3 O.sub.12, Al.sub.1.6 In.sub.0.4 W.sub.3 O.sub.12, Al.sub.1.7 In.sub.0.3 W.sub.3 O.sub.12, Al.sub.1.8 In.sub.0.2 W.sub.3 O.sub.12, YAlW.sub.3 O.sub.12, ScAlW.sub.3 O.sub.12, ScGaW.sub.3 O.sub.12, ScInW.sub.3 O.sub.12, ScHoW.sub.3 O.sub.12, ScYbMo.sub.3 O.sub.12, ErInW.sub.3 O.sub.12, Al.sub.1.68 Sc.sub.0.02 In.sub.0.3 W.sub.3 O.sub.12, Zr.sub.2 WP.sub.2 O.sub.12, Zr.sub.2 MoP.sub.2 O.sub.12, Hf.sub.2 WP.sub.2 O.sub.12 and Hf.sub.2 MoP.sub.2 O.sub.12. A general method for making compounds having low or negative thermal expansion, and compositions containing such compounds, also is described. The first step of the method comprises purposefully designing compounds to be low or negative thermal expansion compounds according to rules derived empirically. The second step comprises making those compounds designed according to the rules. Examples of negative thermal expansion materials made by such method include NbO.sub.2 F and TaO.sub.2 F.

Materials with low or negative thermal expansion

A method for making tungstate compounds according to the formula XW.sub.2 O.sub.8, wherein X is selected from the group consisting of zirconium, hafnium, and combinations thereof, is described. Also described are compositions that include the tungstate compounds, and a method for reducing the positive thermal expansion of a material using such tungstate compounds. Substantially single phase compounds can be made by practicing the method, which method also reduces the synthesis time relative to known methods, and expands the reactants that can be used for the synthesis over the methods reported previously. The tungstate compounds generally can be made by forming a solution, particularly an aqueous solution, comprising a W.sup.6+ compound and a second metal compound wherein the metal is selected from the group consisting of Zr.sup.4+, Hf.sup.4+ and combinations thereof. The solvent is removed from the solution by any known method to leave the solutes as a solid product. The solid product is then heated to a temperature of greater than about 600.degree. C., preferably at least about 1165.degree. C., more preferably from about 1165.degree. C. to about 1250.degree. C., and even more preferably to about 1200.degree. C. The heated product is then cooled to ambient temperature, generally relatively rapidly, to produce substantially single phase tungstate compounds.

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Corvallis, OR, United States of America

John S Evans