Publications

Synthesis and processing of meta-stable negative thermal expansion materials, zirconium tungstate and zirconium phosphotungstate (ZrW2O8 and ZrWP2O12)

Gordon, Margaret E.; Greathouse, Jeffery A.; Weck, Philippe F.; Kim, Eunja; Bryan, Charles R.

Synthetic routes and Direct Current Sintering were investigated to form core-shell structured materials or pellets of negative thermal expansion materials, ZrW2O8 and Zr2WP2O12 to be used as a radionuclide wasteform. The solution synthetic routes, while successful in the growth of additional phase pure ZrW2O8 on the surface of the ZrW2O8 seeds, did not completely encapsulate them. Via Direct Current Sintering, a narrow temperature band of phase stability for ZrW2O8 was identified from 650-700 C at a pressure of 60 MPa. The pellet was partially sintered, showing some void spaces by SEM. Zr2WP2O12 necessitated much higher temperatures to maintain phase purity, at 1400 C and produced a dense pellet.