New (oxy)nitride pearlescent pigments

Thin (d = 60 nm/140 nm) nanocrystalline Ta3N5 and Zr2ON2 films were synthesized in a rotary kiln and in a fluidized bed apparatus. The control of the reaction was performed by optimizing the ammonia flow, the temperature and the reaction time. Using fluidized bed technology, the reaction times were significantly reduced compared to a stationary oven and to a rotary kiln. Movement of the particles in the gas phase favors gas–solid interaction that enhances gas diffusion in the pores. In addition, complete reactions and homogeneous products were obtained in the fluidized bed and not in a rotary kiln, which resulted in pigments having a stronger interference color.