In situ formation of Ni- and Cr-doped cobalt ferrite pigment in glassy matrix films via laser zone melting

Doped cobalt ferrites (CFO, CoFe₂O₄) are black pigments of considerable interest in ceramic systems, although their conventional production requires high-temperature calcination followed by milling to control particle size. In this work, laser zone melting (LZM) is proposed as an alternative route for the in situ formation and consolidation of CFO spinels directly on the surface, avoiding both pre-synthesis and post-micronization. A precursor layer prepared from milled powders was activated using a high-power nanosecond fiber laser. Irradiance and pulse overlap were systematically varied, identifying an optimal processing window at Oₚ ≈ 97%, with a scanning speed of 2,000 mm/s and an irradiance of 3.49 MW/cm². The resulting coatings exhibited distinct crystalline phases together with a vitreous fraction that enabled the integration of ~200 nm particles into the surface, and L* values as low as 30.55. These findings highlight LZM as a promising route toward ceramic industry electrification and decarbonization.