Inorganic Yellow Pigments Research Articles

Yellow rare earth sulfide powders with near‐infrared reflectance and spectral modulation for energy‐saving applications

AbstractRadiative cooling pigments offer new opportunities for sustainable carbon neutrality as zero‐energy and zero‐pollution functional materials. However, it is a challenge to prepare inorganic yellow pigments simultaneously with environmentally friendly, high color value, and weather resistance. In this study, a series of alkali metal‐doped γ‐Sm2S3 yellow pigments with near‐infrared reflectance were synthesized. The doping of alkali metal ions reduced synthesis temperature of Sm2S3 from 1300°C to 1000°C. The change in energy band structure induced by alkali metal doping allows the products to exhibit modifiable colors. Typical γ‐[Na]‐Sm2S3 pigment powders have a high near‐infrared reflectance and impressive colors (b* = 78.6, C* = 77.6). Furthermore, colored films made by prepared yellow powders with polyvinylidene fluoride in certain ratios had high near‐infrared reflectance and excellent environmental weathering, resulting in an effective cooling of 4–8°C in outdoor experiments. This work expands the range of options for energy‐efficient building and yellow colorant.

Enhancing the color of inorganic yellow pigments using yellow fluorescent materials: The case of BiVO4, PbCrO4/(Y,Gd)AG:Ce3+, Sr2SiO4:Eu2+

This paper presents a novel approach to enhancing the color of inorganic yellow pigments using yellow fluorescent materials. The results demonstrate that the inclusion of phosphor leads to a significant improvement in various color attributes. Specifically, the addition of 15 %–20 % phosphor of YAG:Ce3+, (Sr,Ba)2SiO4:Eu2+ or YAG:Ce3+,Gd3+ in BiVO4 or PbCrO4 increases the brightness value (L*) by 5.0 %–8.7 %, the yellowness value (b*) by 4.2 %–9.2 %, and the color saturation value (C*) by 4.1 %–8.7 %. Furthermore, the reflections in the yellow region show a notable increase of 13.7 %–22.1 %, while remaining relatively low in the blue region (the complementary color of yellow), at approximately 10 %. This phenomenon can be attributed to the strong yellow emission performance of phosphor and the interesting synergistic effect between phosphor and pigment. The strong blue absorption of conventional pigment powder compensates for the inherent lack of blue absorption in phosphor alone, thereby maintaining a low reflectivity for the complementary color (blue) of yellow. Moreover, the fluorescence lifetime of yellow substantially increases with the addition of phosphor in the mixed material. This observation aligns with the quantitative relationship between reabsorption and fluorescence lifetime, suggesting widespread reabsorption of yellow emission. This finding supports our hypothesis that positive synergies occur within the mixed layer. In summary, incorporating a small amount of phosphor into conventional pigments effectively enhances the coloring effect of the pigments.

Mechanochemical preparation of low cost kaolinite-based BiVO4 hybrid pigments with high near infrared reflectance

For accelerate construction of the energy and resource-saving and environmental-friendly society, cleaner preparation of low-cost and high-performance colorful near-infrared reflective inorganic pigments with the decorative function is indispensable to reduce the hazards of urban heat island and simultaneously beautify the appearance of the buildings. Due to the non-toxicity, good chemical stability and narrow band gap, BiVO4 has been becoming a promising environment-friendly yellow inorganic pigments among the conventional heavy metals-containing inorganic pigments. In this study, the low-cost and brilliant kaolinite-based BiVO4 hybrid pigments were fabricated by cleaner mechanochemical method based on cheap and abundant kaolinite using crystal water of the hydrated metal salts as trace solvent, which could effectively promote the interaction of the involved components at the molecular level during grinding and then decreased the mass transfer resistance for the formation of monoclinic scheelite BiVO4 in the following calcination. The obtained hybrid pigments at the optimal preparation conditions exhibited brilliant color properties (D65-10°, L * = 83.45 ± 0.08, a * = 4.17 ± 0.08, b * = 88.59 ± 0.17), high near-infrared reflectance of 86.22%, infrared solar reflectance of 88.14% and high emissivity of 0.9369 in the waveband of 8–13 μm. Furthermore, the hybrid pigments could be used for coloring epoxy resin with high emissivity of 0.8782 in 8–13 μm. Therefore, the brilliant and low-cost kaolinite-based bismuth yellow hybrid pigments have the enormous potential to be served as colorful functional nanofillers for cooling roofing materials.

Effect of low molecular weight organic acids on the lead and chromium release from widely-used lead chromate pigments under sunlight irradiation

Lead chromate pigments are commonly used yellow inorganic pigments. They can pose environmental risks as they contain toxic heavy metals lead and chromium. Low molecular weight organic acids (LMWOAs), as widespread dissolved organic matter (DOM), affect the lead and chromium release from the pigment in water. In this work, the role of LMWOAs in the photodissolution of commercial lead chromate pigment was investigated. The pigment underwent significant photodissolution under simulated sunlight exposure with LMWOAs, and subsequently released Cr(III) and Pb(II). The photodissolution process is caused by the reduction of Cr(VI) by photogenerated electrons of the lead chromate pigment. The LMWOAs promoted photodissolution of the pigment by improving the electron-hole separation. The formation of Cr(III)-contained compounds leads to a slower release of chromium than lead. The photodissolution kinetics increase with decreasing pH and increasing LMWOAs concentration. The photodissolution of lead chromate pigment was basically positively related to the total number of hydroxyl and carboxyl groups in LMWOAs. The LMWOAs with stronger affinity to lead chromate pigment, lower adiabatic ionization potential (AIP) and higher energy of the highest occupied molecular orbital (EHOMO) are favorable to Cr(VI) reduction by photogenerated electrons and pigment photodissolution. 2.39% of chromium and 10.34% of lead released from the lead chromate pigment in natural conditions during a 6-h sunlight exposure. This study revealed the photodissolution mechanism of lead chromate pigment mediated by LMWOAs with different molecular structures, which helps understand the environmental photochemical behavior of the pigment. The present results emphasize the important role of DOM in the heavy metals release from commercial inorganic pigments.

Synthesis and characterization of Zn1-xMnxO yellow pigment with high near-infrared reflectance

A series of Zn1-xMnxO (0.001 ≤ x ≤ 0.009) inorganic yellow pigments were prepared by a high-temperature solid-phase method using ZnO and MnO as raw materials. Powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric differential scanning calorimetry (TG-DSC) and so on were applied to test and analyze the designed pigments. The Zn1-xMnxO pigments do not contain rare earth elements. The raw materials required for the production of the pigment are readily available and the cost of raw materials is low. The pigment has a high near-infrared (NIR) solar reflectance of 71.87%–84.02%. The pigment can improve the NIR reflectance of the glaze. The box simulation experiment revealed that the Zn0.995Mn0.005O pigment has better thermal shielding performance than the commercial iron yellow pigment. Additionally, the pigment also has good chemical stability. Therefore, Zn1-xMnxO pigments have potential as cold pigments and can be applied to architectural coatings to achieve energy saving effects.

Synthesis, properties and applications of novel inorganic yellow pigments based on Ni-doped Al2TiO5

Single phase Al2-2xNixTi1+xO5 (0 ≤ x ≤ 0.4) solid solutions were successfully synthesized by solid-phase reaction. The color of the compounds varied from yellow (x = 0.1) to turmeric (x = 0.4) with increasing nickel content. X-ray photoelectron spectroscopy analysis confirmed that the oxidation state of Ni is +2. The UV–Vis absorption spectrum showed that the color of the sample comes from the d-d transition of Ni2+ in octahedral coordination. Owing to excellent high temperature stability, the as-prepared oxide powders (10 wt%) were mechanically mixing with Al2O3 by conventional ball milling to prepare colored alumina ceramics. When Al2O3 is in excess, the blue NiAl2O4 impurity phase appeared, contributing to an intense green color of the Al2O3 ceramics composite. The Vickers micro hardness value of green alumina was higher than that of pure white alumina. The as-prepared samples were also dispersed in PMMA and bright yellow polymer composites were obtained, indicating great potential in polymer colorant.

Synthesis and Color Evaluation of Tb4+-Doped Na2ZrO3 for Inorganic Yellow Pigments

Tb4+-doped sodium zirconate samples, Na2Zr1−xTbxO3, were synthesized as novel environmentally friendly inorganic yellow pigments by a conventional solid-state reaction method. Their crystal structures, optical properties, and colors were characterized. A single-phase form was obtained for the samples in the x range of x ≤ 0.18, while impurity phases were detected for the sample with x = 0.20. All samples showed strong optical absorption in the blue light region, due to the charge transfer transition between O2− and Tb4+. As a result, the sample color became yellow, which is the complementary color of blue, and the color became more vivid with increasing Tb4+ content in the single-phase region. Among the samples, Na2Zr0.82Tb0.18O3 was the optimal composition, with the highest yellowness (b* = +67.2) and pure yellow hue (h° = 90.1). Although the b* value was lower than commercial yellow pigments such as BiVO4 and ZrSiO4:Pr, this sample had a purer yellow hue. Since Na2Zr0.82Tb0.18O3 is composed of non-toxic elements, it could be a new environmentally friendly inorganic yellow pigment.

Non-ammonolysis synthesis and characterisation of environmentally benign yellow pigments based on calcium–tantalum perovskite oxynitrides

Calcium–tantalum based perovskite oxynitrides were successfully prepared without ammonolysis. The colour of La3+-doped CaTa(O,N)3 was comparable to that of CaTaO2N prepared by ammonolysis and inorganic yellow pigments using heavy metals.

Chromate and molybdate pigments

AbstractChromate and molybdate pigments are representatives of the inorganic yellow, orange and red pigments. They are characterized by excellent optical and application properties in particular regarding brightness of shade, hiding power, tinting strength, and weather fastness. The declining use of lead- and chromate-containing materials in the last decades is a result of the environmental discussion and the development of less problematic substitute products, especially of bismuth vanadate and high-value organic, temperature-stable yellow and red pigments.

Bismuth vanadate pigments

Abstract Bismuth vanadate pigments belong to the most important inorganic yellow pigments since their market introduction in the 1970s. They have substituted the greenish yellow lead chromate and cadmium sulfide pigments in a considerable number of applications. Bismuth vanadate pigments are based on bismuth vanadate with monoclinic or tetragonal structure. Their composition ranges from pure BiVO4 up to the mixed pigment 4BiVO4▪3Bi2MoO6, where molybdenum is incorporated in the structure. Bismuth vanadate pigments are characterized by excellent optical and application characteristics in particular regarding brightness of shade, hiding power, tinting strength, weather fastness, and chemical resistance.

Cadmium sulfide / selenide pigments

AbstractCadmium sulfide and selenide pigments (cadmium pigments) belong to the inorganic yellow, orange and red pigments. Cadmium sulfide pigments are based on the wurtzite lattice, where cadmium can be partially substituted by zinc or mercury and sulfide by selenide. Cadmium pigments are characterized by excellent optical and application characteristics in particular regarding brightness of shade, hiding power, tinting strength, and weather fastness. The declining use of cadmium-containing materials in the last decades is a result of the environmental discussion and the development of less problematic substitute products, especially of bismuth vanadate and high-value organic, temperature-stable yellow and red pigments.

Synthesis and Characterization of Ca1-x Eu x ZrO3 as Environmentally Friendly Inorganic Yellow Pigments.

Eu2+-doped calcium zirconates, Ca1–xEuxZrO3 (0 ≤ x ≤ 1), were synthesized as novel environmentally friendly inorganic yellow pigments by the conventional solid-state reaction method. The crystal structure, morphology, optical properties, and color were characterized. The Eu2+-doped samples strongly absorbed blue light in the wavelength range of 435–480 nm, which was caused by the 4f–5d allowed transition of Eu2+. The color of the sample gradually became brilliant yellow with increasing the Eu2+ content. Among the samples synthesized in this study, the brightest yellow color was obtained with the Ca0.7Eu0.3ZrO3 (a* = +11.5 and b* = +70.7) sample. Compared with the commercially available praseodymium yellow pigment (a* = −3.28, b* = +70.3), the yellowness value (b*) of Ca0.7Eu0.3ZrO3 was comparable and the redness value (a*) was higher. As a result, this pigment exhibited a reddish yellow color as compared with praseodymium yellow. In addition, this pigment was chemically stable. Therefore, the Ca0.7Eu0.3ZrO3 pigment has the potential to become a novel environmentally friendly inorganic yellow pigment.

New environmental-friendly yellow pigments Y4–xAxMoO9+δ (A =Ta, Tb)

A series of inorganic yellow pigments with general formula Y4–xAxMoO9+δ (A = Ta, Tb), where x = 0, 0.05, 0.1, 0.2, 0.4 for Ta and x = 0, 0.005, 0.01, 0.03, 0.05 for Tb, were synthesized by a conventional ceramic method at 1400 °C for 6 h in air. The samples were characterized by XRD, EDS, XPS, SEM, TG-DSC, UV-vis-NIR reflectance spectroscopy and CIE L*a*b* color scales. It is found that the substitution of A (A = Ta, Tb) for Y3+ in Y4MoO9 decreases the NIR reflectance of the pigment samples, but the developed pigments Y4–xAxMoO9+δ (A = Ta, Tb) still exhibit impressive NIR solar reflectance. The brighter yellow color of inorganic pigments Y4–xAxMoO9+δ (A = Ta, Tb) is available when x is about 0.1 for Ta and 0.01 for Tb. The results make them a series of potential candidates as ecological yellow pigments because of their high reflectance, lightness, intense coloration and excellent thermal and chemical stability.

KAOLIN REFLECTANCE SPECTROSCOPY: USING PLS-R TO PREDICT CONTAMINANT CONTENT

The present study deals with the prediction of contaminant concentrations in kaolin using Partial Least Squares Regression (PLS-R). The aim is to show that PLS-R method can be used to predict contaminant concentration in kaolin. High level kaolin means a kaolin with high-brightness. Since brightness is directly related to the reflectance spectrum and kaolin contaminants affect the reflectance spectrum it is important to the beneficiation of kaolin relates optical features and contaminants. Depending on the product to be produced, the optical parameters will influence how the kaolin will be processed. High-brightness kaolin and two red and yellow inorganic pigments were used to simulate colours contaminants frequently found in Brazilian kaolins, such as, hematite, goethite, rutile and anatase. By adding different pigment concentrations to the pure kaolin, it was possible to create a small dataset containing the visible reflectance spectrum of each sample with the respective optical quality parameters of the kaolin. Results allow us to conclude that PLS-R can predict through the reflectance spectrum the contaminant concentration of the kaolin with R-squared equal 0.9954 for red content and R-squared equal 0.9973 for yellow one.

Improved coloristic properties and high NIR reflectance of environment-friendly yellow pigments based on bismuth vanadate

Herein, fine powders of yellow pigments based on BiVO4 were successfully prepared in two crystalline forms, tetragonal zircon-structured and monoclinic scheelite-structured, through a ethylene glycol-assisted method subjected to a thermal treatment at two different temperatures. The obtained materials were brightly colored with different hues of yellow, exhibited high reflection in the near-infrared region and showed visible luminescence under excitation by UV light. The new preparation method had a considerable effect on chromatic properties of the prepared scheelite-structured BiVO4 pigments. The sample with the most vivid and bright shade of yellow was found to have the L*a*b* and L*C*ab h*ab color coordinates of (87.28, 0.37, 91.53) and (87.28, 91.53, 89.79), which are indicative of exceptionally good chromatic properties superior and/or comparable to those of other inorganic yellow pigments, both commercially available and recently described. In addition, the NIR reflectance of this powder was very high (≥ 80%).

Low temperature synthesis of NIR reflecting bismuth doped cerium oxide yellow nano-pigments

A new series of yellow inorganic pigments possessing high solar reflectance based on bismuth doped cerium dioxide was synthesized by sol-gel hydrothermal method at 150 °C for 24 h. The band gap of developed nano-pigments changes from 2.89 to 2.58 eV, displaying colors ranging from pale yellow to bright yellow.

Synthesis and characterization of PrxZr1-xSiO4 (x = 0–0.08) yellow pigments via non-hydrolytic sol-gel method

Yellow inorganic pigments PrxZr1-xSiO4 (x = 0–0.08) have been prepared by a novel non-hydrolytic sol-gel (NHSG) method at 750 °C for 2 h. Replacing Pr4+ for Zr4+ in ZrSiO4 increased the cell volume and changed the color from white to yellow gradually. The Si―O―Zr and Si―O―Pr bands were observed in the FT-IR spectra of xerogel, indicating it could reach homogeneous mixing at the atomic level. Therefore, it promoted the solid solution reaction between Pr and zircon at low temperature. The samples exhibit high doping limitation (x = 0.08) and brilliant yellow hue (b* = 69.48) in contrast with the previously reported praseodymium zircon yellow pigments. The intense of yellow hue was increased with increasing the Pr doping content due to the increase of Pr4+/Pr3+ species. After applying on bisque ceramic tiles, the pigment exhibited excellent coloration, high thermal stability and low solubility in molten glazes, indicating its potential application in ceramic decoration.

Eu and Cu co-substituted calcium vanadate — The crystal structure, luminescence and color

Europium- and copper-doped calcium vanadates with the general formula Ca3-1.5x-yEuxCuy(VO4)2 (x = 0, 0.075; y = 0, 0.06 and 0.18) were synthesized by the solid state reaction. Synthesized materials were analyzed by the powder X-ray diffraction (PXRD), UV–Vis, Raman, luminescence spectroscopy, and colorimetry. Unit cell dimensions of the obtained samples were analyzed by the Rietveld refinement of the PXRD data. The crystal symmetry corresponds to the R3c group. Europium-doped samples exhibited luminescent properties, typical for the majority of europium-containing inorganic compounds. Additional copper-doping partially suppressed the europium luminescence. The europium-and-copper-doped samples possess bright yellow colors. Thus, obtained materials are perspective for the application as inorganic yellow pigments.

Novel environment-friendly yellow pigments based on praseodymium(III) tungstate

The novel environment-friendly inorganic yellow pigments, (Pr1-xCex)2W2O9+δ (0<x≤0.12) with the monoclinic structure, were synthesized and their color properties were investigated. The (Pr1-xCex)2W2O9+δ (0<x≤0.12) samples showed brilliant yellow color by doping trivalent Ce3+ into the Pr2W2O9 lattice due to the optical absorption in blue light region caused by the 4f-5d transition of Ce3+. According to the XPS and Rietveld analysis results, cerium ions in the crystal lattice have two different oxidation states of 3+ and 4+, in which the rate of each oxidation state is 58%:42%, and the Ce3+ and Ce4+ ions are preferentially occupied the PrO9 and the PrO8 polyhedral sites, respectively. Among the samples prepared, the (Pr0.90Ce0.10)2W2O9+δ pigment exhibited the most vivid yellow hue with high color durability for light and acid/base solutions.

SYNTHESIS OF ENVIRONMENTALLY FRIENDLY (Bi, Ca, Zn)VO4 INORGANIC YELLOW PIGMENTS

In this paper, the synthesis of scheelite based environmentally friendly inorganic yellow pigments was presented. The pigments of Bi1-x-yCaxZnyVO4-(x+y)/2 (x = 0.1 ÷ 0.9, y = 0.1 ÷ 0.9) have been prepared by the evaporation to dryness from BiONO3, Ca(NO3)2.4H2O, Zn(NO3)2.6H2O and NH4VO3. The obtained powders were characterized by Thermal Analysis (TG-DSC), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and CIE L*a*b* colour measurement. The results showed that the pigments calcinated at 650oC for 6 hours with the heating rate of 5oC.min-1 possessed single phase of scheelite with good crystallinity. The yellow colour intensity was a function of the amount of calcium (II) and zinc (II) ions. The colour of Bi0.70Zn0.30VO3.85 sample was similar to the lemon yellow PbCrO4 (BASF1522) pigment made by Hangzhou Emperor Pigment Company (China).