Preparation and electrical properties of V-Sm-Y-O pigments for black alumina ceramics

Rare earth elements occupy a significant position in the field of ceramic pigments due to their distinctive electronic structure and physicochemical properties, which can markedly enhance the chromaticity and improve the electrical insulation properties of ceramic pigments. In this study, a novel cobalt-free V-Sm-Y oxide pigments were employed to fabricate black alumina ceramics that possess a deep black coloration and a high volume resistivity. The results revealed that, under a reducing atmosphere, the V oxide undergoes interaction with rare earth elements to form structurally stable crystalline phases, primarily SmVO₃ and YVO₃. These phases exhibit a distinct color-presenting effect, resulting in an intense black hue. Specifically, when the V-Sm-Y ratio is 1:0.25:0.25, the ultraviolet reflectance value of the color pigment reaches 5.21. The black color of the pigment is primarily attributed to electron transitions occurring in the 4f orbitals of Sm and Y elements, as well as in the 4d orbital of V element, which efficiently absorb visible light. The pigment exhibits a volume resistivity of 8.65 × 10⁸ Ω·cm at room temperature, whereas the black ceramics produced with 10 wt% of this pigment and sintered at 1550 °C under a hydrogen atmosphere demonstrate an enhanced volume resistivity of 8.69 × 10¹³ Ω·cm.