A microwave plasma apparatus for processing a material includes a plasma chamber, a microwave radiation source, and a waveguide guiding microwave radiation from the microwave radiation source to the plasma chamber. A process gas flows through the plasma chamber and the microwave radiation couples to the process gas to produce a plasma jet. A process material is introduced to the plasma chamber, becomes entrained in the plasma jet, and is thereby transformed to a stream of product material droplets or particles. The product material droplets or particles are substantially more uniform in size, velocity, temperature, and melt state than are droplets or particles produced by prior devices.