**Abstract**

Micro-sized spherical AlN particles have presented great commercial potential as thermally conductive fillers for high-performance thermal interface materials, benefiting from their high thermal conductivity and good fluidity in the polymers. In this chapter, recent research progress in the carbothermal synthesis of spherical AlN fillers is highlighted. The influences of various synthetic parameters, including N2 gas pressure, additive content, additive particle size, reaction temperature, reaction time, carbon content, and additive types, on the nitridation rate and the particle size and morphology of final AlN powders are summarized. More importantly, the growth mechanism of micro-sized spherical AlN granules is deeply discussed as well.

**Keywords:** carbothermal synthesis, spherical AlN particles, thermally conductive fillers, thermal interface materials, growth mechanism
