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Solution method for making molybdate and tungstate negative thermal expansion materials and compounds made by the method

  • US 6,183,716 B1
  • Filed: 07/30/1998
  • Issued: 02/06/2001
  • Est. Priority Date: 07/30/1997
  • Status: Expired due to Fees
First Claim
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1. A method for making substantially single-phase, crystalline NTE compounds having the formula:

  • A4+

    M26+

    O8
    where A4+ is Zr4+, Hf4+, or mixtures thereof, and M6+ is Mo6+, W6+, or mixtures thereof, the method comprising;

    forming a liquid mixture comprising stoichiometric amounts of (1) a soluble source of Zr4+, Hf4+, or mixtures thereof, and (2) a sodium-ion-free tungstate salt, a sodium-ion-free molybdate salt, or mixtures thereof;

    adding an acid to the liquid mixture to acidify the liquid mixture;

    refluxing the liquid mixture at ambient pressures for a period of about 48 hours or more, or at pressures greater than ambient for a period of from about 1 to about 24 hours;

    separating a solid fraction from the mixture; and

    heating the solid fraction to a temperature within the temperature range of from about 500°

    C. to less than 700°

    C. to form a compound having the formula A4+

    M26+

    O8.

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