Methods and apparatus for the production of ultrafine particles

A method for reducing the average primary particle size of ultrafine particles made by a vapor phase synthesis process comprising:

• (a) including an alkali metal dopant in a precursor stream to a high temperature chamber, wherein the precursor stream comprises at least one organometallic and/or inorganic oxide precursor which is different from the alkali metal dopant;
• (b) heating the precursor stream in the high temperature chamber, yielding a gaseous product stream;
• (c) quenching the gaseous product stream, thereby producing ultrafine particles;
• and (d) collecting the ultrafine particles.

A plasma reactor apparatus for the production of ultrafine particles comprising:

• (a) a plasma chamber having axially spaced inlet and outlet ends;
• (b) a high temperature plasma positioned at the inlet end of the plasma chamber;
• (c) an inlet for introducing a precursor stream to the plasma chamber, the precursor stream comprising:
• (i) a first precursor;
• and
• (ii) a second precursor different from the first precursor and comprising an alkali metal dopant, wherein the precursor stream is heated by the plasma to produce a gaseous product stream flowing toward the outlet end of the plasma chamber;
• (d) means for quenching the gaseous product stream, thereby producing ultrafine particles, and
• (e) means for collecting the ultrafine particles.