Patent ID: 8097202

Claim:
A powder metallurgy process for the manufacture of a refractory ceramic material comprising: hafnium dioxide HfO 2 grains having a monoclinic structure; hafnium dioxide HfO 2 grains having a cubic structure, which is stabilized by yttrium oxide Y 2 O 3 , said yttrium oxide Y 2 O 3 representing 0.5 mol % to 8 mol % relative to the total number of moles of hafnium dioxide HfO 2 ; non-interconnected open pores; closed pores; said process comprising the consecutive steps of: (i) obtaining a dry mixture of a hafnium dioxide HfO 2 powder and an yttrium oxide Y 2 O 3 powder, each of these oxides being mixed in the molar proportions in which it is found in said ceramic material; (ii) step of granulation by pelletization of said dry mixture under stirring in order to obtain a granulated mixture, said granulation step comprising the spraying, into the dry mixture, of an aqueous solution comprising, relative to the weight of the dry mixture, 5% by weight of polyvinyl alcohol (PVA) binder having a molecular weight in the range between 50000 and 90000 g/mol and 5% by weight of polyethylene glycol (PEG) plasticizer having a molecular weight in the range between 180 and 420 g/mol; (iii) drying of said granulated mixture; (iv) filling of a mold with said granulated mixture; (v) isostatical or semi-isostatical pressing of said granulated mixture filling said mold, in order to obtain a compact mixture; (vi) sintering of said compact mixture in order to obtain said refractory ceramic material comprising grains having a cubic structure and grains having a noncubic structure.