It is not fusion. Fusion means adding something (atomic nucleus) at very high temperature. It is grinding or milling of the powder sample. Fission means breaking something at very high temperature.
The noun fusion comes from the Latin word fundere, meaning melt. Current dictionaries define the fusion as:
• The act or procedure of liquefying or melting by the application of heat.
• A nuclear reaction in which atomic nuclei combine to form moremassive nuclei with the simultaneous release of energy.
None of the two concepts has anything to do with the quality of the powders. Maybe you wanted to refer you to heat treatment (calcination) used powder manufacturing?