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Novel blue pigments based on Ba 0.956 Mg 0.912 Al 10.088- x Ni x O 17 (0 ≤ x ≤ 0.3) and Ba 0.956 Mg 0.912 Al 10.088- x Co x O 17 (0 ≤ x ≤ 0.3) solid solutions were successfully synthesized by solid state method. The XRD results confirmed the structure of the as-synthesized sample belongs to hexagonal β -alumina structure with the space group of P 6 3 / mmc. The d-d electron transitions in Ni2+/Co2+ tetrahedral sites in the visible light range are the reason for the blue colors. Then, the as-prepared blue oxides were sintered with ZrO 2 powders at 1400 °C to prepare blue zirconia ceramic materials. Based on XRD and SEM analysis, the pigment phase is stable after high-temperature sintering with ZrO 2 , and a clear grain boundary is observed. The XCT results indicate the prepared blue ceramics are dense and very small pores are rarely distributed inside the blue zirconia ceramic body. Additionally, the mechanical properties of the fabricated blue ceramics were maintained compared to pure ZrO 2 ceramic. [ABSTRACT FROM AUTHOR]

The novel orange to red color Bi 24 Al 2- x Cr x O 39 (0≤ x ≤ 0.5) compounds were successfully synthesized by the solid state method. With the increase of Cr content, the colors of compounds are tuned from orange red to dark red. The X-ray diffraction patterns of all samples are indexed with cubic Bi 24 Al 2 O 39 structure with the space group of I 23. The oxidation state of Cr in the oxide is confirmed to be +4 valence by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Based on the analysis of Cr oxidation state and UV–Visible spectrum, the red hue is due to the d-d transition of Cr4+ in tetrahedral sites. The as-synthesized red color compounds also show excellent stability in acid and base environments. [ABSTRACT FROM AUTHOR]

Novel green and blue chromophores based on Ni/Co/Cr doped BaMg 6 Ti 6 O 19 solid solutions are successfully synthesized through a solid-state reaction. The crystal structure of all the samples belongs to the magnetoplumbite structure with the space group of P 6 3 / mmc. The BaMg 6- x /2 Ti 6- x /2 Ni x O 19 (0 ≤ x ≤ 0.3) compounds exhibit a light green (x = 0.1) to yellow-green (x = 0.3) color. The oxidation state of Ni is confirmed to be +2 valence and the d-d transition of Ni2+ in octahedral sites is responsible for color. BaMg 6- x /2 Ti 6- x /2 Co x O 19 (0 ≤ x ≤ 0.3) series show a blue color and the intensity of blueness is increasing with the increase of Co content. The blue color is due to d-d transitions within Co2+ present in the tetrahedral sites. For BaMg 6- x /2 Ti 6- x /2 Cr x O 19 (0 ≤ x ≤ 2) phases the color varies from light green (x = 0.2) to green (x = 2). Chromium exists in +3 and + 6 oxidation states and the observed color is due to charge transfer transition between Cr3+–Ti4+ and d-d transitions within octahedral Cr3+ sites resulting in strong absorption in the visible region. The synthesized colored oxides are mixed with PMMA to prepare novel green and blue PMMA polymer composites to evaluate their compatibility in plastics. [ABSTRACT FROM AUTHOR]