Bismuth-doped y2moo6 high near-infrared reflective yellow pigments, methods of making and applications thereof

Abstract

The application discloses a kind of Y2MoO6 high near-infrared reflection yellow pigments based on bismuth doping and its preparation method and application, the general formula of the yellow pigment is Y 2‑x Bi x MoO 6， Wherein: Bi is doping element, x represents the doping molar amount of Bi, 0 2‑x Bi x The yellow pigment has good crystallinity and complete solid solution formation. The yellow pigment has a monoclinic structure, and the space group is C2 / c (15). At a wavelength of 1100 nm, the near-infrared reflectivity of the pigment is 99% to 103%. As the bismuth doping amount increases, the Y 2‑x Bi x MoO6 pigment color gradually deepens, and the reflectivity first increases and then decreases.

Description

Technical Field

[0001] This invention belongs to the field of inorganic pigments, specifically relating to an environmentally friendly Y2MoO6 high near-infrared reflectance yellow pigment based on bismuth doping, its preparation method, and its application. Background Technology

[0002] While urban development brings convenience and comfort, it also brings a series of problems such as energy consumption and the urban heat island effect. With the concentration of cities and industrial development, almost half of the energy used in urban buildings is related to heating, ventilation, or air conditioning (HVAC). Climate and environmental issues are receiving increasing attention. To address the energy consumption and urban heat island problems caused by urbanization, many solutions have been researched and explored. Since buildings and roofs account for approximately 25% of the total urban surface area, pigments and coatings with high solar reflectivity have received widespread attention. Their importance lies not only in their ability to be applied to numerous urban buildings for decorative purposes, but also in their ability to reflect solar heat radiation, maintaining a certain temperature gradient between the interior and exterior of buildings. While ensuring indoor comfort and livability, coatings help reduce the use of equipment such as air conditioning, thereby reducing the demand for building energy consumption. This helps reduce building energy consumption and carbon dioxide emissions, and also reduces the impact of urban heat accumulation and urban smog. Near-infrared reflective pigments have been widely used in the research of "cold pigments" in the construction field. These pigments exhibit a "cold pigment" effect because only 43% of total solar radiation is visible light, with nearly half reaching the Earth's surface in the near-infrared form. Replacing traditional coatings with high near-infrared reflective cold coatings can effectively reduce building thermal gain. This provides significant room for research into inorganic high near-infrared reflective pigments.

[0003] According to research in the field of optics on the range of visible light wavelengths perceived by the human eye, yellow is a very eye-catching color. The human eye can only perceive light with wavelengths between 400-780 nm, with greater sensitivity to this range. Sensitivity is extremely high at a wavelength of 555 nm. This wavelength corresponds to the yellow-green region. Therefore, traffic signs, taxis, telephone booths, and cranes—places requiring high visibility—are often painted a striking yellow. Although lead chromate yellow holds an important position among inorganic yellow pigments, its widespread application has been hindered by the presence of lead. In 1992, EU legislation stipulated that all compounds containing at least 0.5% lead are hazardous substances, pointing the way for the development of inorganic yellow pigments. The use of lead-free pigments in industrial coatings is increasingly trending. Among inorganic pigments, iron yellow pigment has an unsatisfactory hue. Organic yellow pigments suffer from high cost, poor coverage and stability, and relatively complex synthesis processes. Research on economical inorganic yellow pigments that are brightly colored, perform well, and do not contain toxic metals is receiving increasing attention.

[0004] Inorganic optoelectronic materials, such as transition metal molybdates, possess unique electronic, chemical, and optical properties. Doping has become an effective means of modifying inorganic optoelectronic materials to adjust their band gap and optical properties. By adding different dopants, the properties of inorganic optoelectronic materials can be effectively altered, and their optical properties can be tuned. Based on the energy level transitions of the matrix material, rare earth doping can enhance its optical properties and has been extensively studied in areas such as high near-infrared reflectance, luminescence, and fluorescence. Due to their low toxicity and unique optical properties, rare earth elements are considered promising elements in the field of inorganic pigments. These elements not only avoid the use of highly toxic chromophores, such as cobalt, chromium, or cadmium, but also exhibit excellent optical properties. The unique properties of rare earth elements in the 4f orbital contribute to improving the performance of inorganic pigments. For example, bismuth is often used as a chromophore ion in inorganic pigments, and the introduction of lanthanides can change the original oxidation state of bismuth, thereby altering its color. These lanthanides not only act as chromophores in the pigment structure but can also regulate the oxidation state of other components within the crystal lattice, changing the crystal field and thus affecting the final color of the pigment powder. The band gap of the prepared rare earth pigments exceeds the energy of near-infrared light, which helps to prevent electron transitions, achieve high near-infrared light reflectivity, improve photothermal stability, and extend service life.

[0005] Yttrium is an important, highly abundant rare earth element, widely produced in the ion adsorption rare earth separation industry. Yttrium molybdate (Y₂MoO₆) is an important inorganic optoelectronic material, commonly used in fluorescence luminescence and dielectric applications. However, there are few reports on how to develop pigments with good color performance, low cost, and simple preparation processes based on the high near-infrared reflectivity of Y₂MoO₆. Summary of the Invention

[0006] Studies have found that by modifying or doping Y₂MoO₆, its hue can be altered to create hues with promising application prospects, thus enabling it to play a role in the pigment and coating field. Y₂MoO₆ is an A₂BO₆ compound, and compounds with A₂BO₆ stoichiometry typically possess simple and robust crystal structures. Their A and B positions readily bind to various chromophore ions through doping, exhibiting excellent color rendering properties. Therefore, this invention employs a high-temperature solid-state method to prepare a Bi-doped Y₂MoO₆ yellow pigment and analyzes its color characteristics. Furthermore, its near-infrared reflectance, acid and alkali stability, high-temperature resistance, and coating properties were investigated to analyze the multifunctional application potential of the prepared yellow pigment.

[0007] The technical solution of the present invention is as follows:

[0008] A yellow pigment, wherein the general formula of the yellow pigment is Y 2-x Bi x MoO 6， in:

[0009] Bi is the doping element, x represents the molar amount of Bi doping, 0 < x < 0.3;

[0010] For example, x is 0.01, 0.02, 0.05, 0.08, 0.1, 0.15, 0.2, 0.25, 0.28, or 0.29.

[0011] According to an embodiment of the present invention, the yellow pigment has a crystalline structure, which is monoclinic and has a space group of C2 / c(15). α=90°; β=108.5°; γ=90°.

[0012] According to an embodiment of the present invention, the average particle size of the yellow pigment is 1 to 30 μm.

[0013] According to an embodiment of the present invention, the average reflectance of the near-infrared reflectance spectrum of the yellow pigment is not less than 104%, for example, 104%-107%. It should be noted that the reflectance of the present invention is relative to the comparative material barium sulfate, and the reflectance of barium sulfate as a reflectance standard is well known in the art.

[0014] According to an embodiment of the present invention, the near-infrared reflectance of the yellow pigment at a wavelength of 1100 nm is 99% to 103%, for example, 99.9% to 103%.

[0015] The present invention also provides a method for preparing the above-mentioned yellow pigment, wherein the method is as follows:

[0016] Using Y, Bi, and Mo sources as raw materials, according to the chemical formula Y 2-x Bix The yellow pigment is obtained by mixing the elements in MoO6 according to their stoichiometric ratios and then sintering them in a solid state.

[0017] According to an embodiment of the invention, the Y source is provided by a compound containing the element Y; for example, by at least one of carbonates, oxides, chlorides, nitrates and sulfates containing the element Y; preferably by an oxide containing the element Y (e.g., Y₂O₃).

[0018] According to an embodiment of the invention, the Bi source is provided by a Bi-containing compound. For example, it is provided by at least one of Bi-containing carbonates, oxides, chlorides, nitrates, and sulfates; preferably, it is provided by a Bi-containing oxide (e.g., Bi₂O₃).

[0019] According to an embodiment of the invention, the Mo source is provided by a Mo-containing compound; for example, by at least one of a Mo-containing carbonate, oxide, chloride, nitrate, and sulfate; preferably by a Mo-containing oxide (e.g., MoO3).

[0020] According to an embodiment of the present invention, the solid-state sintering temperature is 400℃~1300℃, and the solid-state sintering time is 4-10h.

[0021] Preferably, the solid-state sintering is first held at 400-550℃ (exemplary: 400℃, 450℃, 500℃ or 550℃) for 1-3 hours, and then held at 550-1300℃ (exemplary: 800℃, 900℃, 1000℃, 1100℃, 1200℃ or 1300℃) for 4-10 hours, exemplary: 4 hours, 6 hours, 8 hours or 10 hours.

[0022] According to an embodiment of the present invention, the heating rate of the solid-state sintering is 1 to 10 °C / min, exemplarily 1 °C / min, 2 °C / min, 5 °C / min, 8 °C / min, 10 °C / min, preferably 8 °C / min.

[0023] According to an embodiment of the present invention, prior to the solid-state sintering treatment, a grinding step of the raw material is further included. For example, the grinding can be wet grinding or ball milling; preferably, the grinding medium can be at least one of acetone, water, and ethanol, preferably acetone. Preferably, the grinding time is 2 to 6 hours, for example, 2 hours, 4 hours, or 6 hours. Further, the grinding speed is 200 to 600 rpm.

[0024] According to an embodiment of the present invention, the preparation method further includes a step of drying the ground raw material. For example, the drying temperature is 40-60°C, exemplarily 40°C, 50°C, or 60°C, preferably 60°C. Further, the drying time can be 0.5-2 hours, exemplarily 0.5 hours, 1.5 hours, or 2 hours, preferably 2 hours.

[0025] According to an embodiment of the present invention, the preparation method further includes cooling the product after solid-state sintering is completed, wherein the preferred cooling rate is below 2°C / min.

[0026] Preferably, after cooling, the calcined sample is ground. Preferably, the average particle size of the calcined sample after grinding is 1–30 μm.

[0027] According to an exemplary embodiment of the present invention, the preparation method includes the following steps:

[0028] According to the chemical formula Y 2-x Bi x The stoichiometric ratio of each element in MoO6 was determined by weighing Y source, Bi source and Mo source in sequence, adding grinding media (e.g. acetone) for grinding, drying the ground mixture and performing solid-state sintering treatment, and then grinding the calcined sample again to obtain a yellow pigment.

[0029] The present invention also provides the application of the above-mentioned yellow pigment in the fields of building materials, coatings, plastics, vehicles, ship decks, aerospace, oil tanks or inks.

[0030] The beneficial effects of this invention are:

[0031] This invention employs a high-temperature solid-state synthesis method to synthesize a series of compounds with the general formula Y. 2-x Bi x An environmentally friendly inorganic yellow pigment of MoO6 is described, exhibiting good crystallinity and complete solid solution formation. The yellow pigment has a monoclinic structure with space group C2 / c(15). At a wavelength of 1100 nm, the near-infrared reflectance of the pigment is 99%–103%. With increasing bismuth doping concentration, Y... 2-x Bi x The color of MoO6 pigment gradually deepens, and its reflection initially increases and then decreases.

[0032] This invention Y 1.8 Bi 0.2 MoO6 (i.e., x = 0.2) yellow pigment has excellent reflectivity and yellow color, as well as good chemical stability and heat retention properties.

[0033] The pigments of the present invention (especially Y) 1.8 Bi 0.2MoO6 helps reduce the internal temperature of buildings and exhibits good stability during use.

[0034] In summary, the environmentally friendly yellow pigment prepared by this invention does not contain toxic heavy metals. It possesses excellent near-infrared reflectance properties, acid and alkali stability, high-temperature resistance, and relatively low cost, showing potential application prospects in the field of cool-colored pigments. Yttrium is a high-abundance rare earth element in ion-adsorption rare earth separation industry, and this invention demonstrates the new application potential of yttrium in optical functional materials. Attached Figure Description

[0035] Figure 1 The yellow pigment Y in Example 1 2-x Bi x XRD patterns of MoO6 (x values ​​of 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3).

[0036] Figure 2 The yellow pigment Y in Example 1 1.8 Bi 0.2 A schematic diagram of the crystal structure of MoO6.

[0037] Figure 3 The yellow pigment Y in Example 1 2-x Bi x SEM images of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively).

[0038] Figure 4 The yellow pigment Y in Example 1 1.8 Bi 0.2 EDS plot and elemental distribution map of MoO6.

[0039] Figure 5 The yellow pigment Y in Example 1 1.8 Bi 0.2 XPS scan full spectrum (a) and fine scan spectrum (be) of MoO6.

[0040] Figure 6 The yellow pigment Y in Example 1 2-x Bi x Particle size distribution of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively).

[0041] Figure 7 The yellow pigment Y in Example 1 2-x Bi x Absorption spectra of MoO6 (x = 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively).

[0042] Figure 8 The yellow pigment Y in Example 1 2-x Bi x Absorption limit diagrams for MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively).

[0043] Figure 9 The yellow pigment Y in Example 1 2-x Bi x L of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively) * a * b * value.

[0044] Figure 10 The yellow pigment Y in Example 1 2-x Bi x CIE 1931 chromaticity coordinates of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively).

[0045] Figure 11 The yellow pigment Y in Example 1 2-x Bi x Physical images of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively).

[0046] Figure 12 The yellow pigment Y in Example 1 2-x Bi x Average reflectance of near-infrared reflectance spectrum (a) and average reflectance of near-infrared solar reflectance spectrum (b) of MoO6 (x = 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively).

[0047] Figure 13 For Y in test example 8 1.8 Bi 0.2 Internal temperatures of the MoO6-coated model (experimental group) and the uncoated model (control group) at different time points. Detailed Implementation

[0048] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0049] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0050] In this embodiment of the invention, rare earth Y₂O₃ was purchased from Sahn Chemical Technology (Shanghai) Co., Ltd., with a purity of 99.99%. MoO₃ was purchased from Adamas-Beta (Shanghai) Co., Ltd., with a purity of 99.99%. Bi₂O₃ was from Aladdin Reagent (Shanghai) Co., Ltd., with a purity of 99.9%. The above reagents require no further purification and can be used directly in the experiment. The experiment used purified water after removing ionic impurities, with a resistivity greater than 18 MΩ / m, meeting the laboratory deionized water standard.

[0051] Example 1

[0052] Bismuth-doped yellow pigment powder Y was synthesized using a high-temperature solid-state method. 2-x Bi x MoO6, the specific method is as follows:

[0053] Y₂O₃, Bi₂O₃, and MoO₃ raw materials were used to synthesize sample Y according to the target synthesis method. 2-x Bi x The stoichiometric proportions of MoO6 (where x represents 0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) were weighed to four decimal places. After thorough mixing, acetone was added and the mixture was ground in agate slurry until the acetone evaporated. The experimental process was repeated 3-4 times to obtain a mixture. The mixed powder was dried in an oven at 60°C for at least 4 hours to allow the mixed acetone to evaporate. The completely dried pretreated powder mixture was then poured into a corundum crucible and placed in a muffle furnace for a high-temperature solid-state reaction. First, the muffle furnace was heated to 550°C at a rate not exceeding 10°C / min and held at this temperature for 1 hour. This step is because the MoO3 in the raw materials evaporates significantly at 550°C. Then, the muffle furnace was heated to the synthesis temperature of 1200°C at the original rate and held for 4 hours. After the high-temperature solid-state reaction was completed, the product was cooled at a rate of less than 2°C / min. This cooling rate allows sufficient time for the product to crystallize, thus avoiding local saturation. Therefore, the crystal phase structure is more stable. This reduces the possibility of crystal defects in the experiment and improves crystal purity. The sample obtained from the reaction is milled 2-3 times in acetone medium to disperse the sample, which helps to eliminate sintering caused by high temperature. Then the drying step of the pretreatment stage is repeated to obtain the final desired pigment sample, namely a high near-infrared reflectance yellow pigment.

[0054] The calcined product with x = 0 is referred to as Comparative Example 1, or undoped pigment. The calcined products prepared with x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3 are referred to as doped yellow pigment.

[0055] The phase composition and crystal form of the calcined samples were determined using a Miniflex 600 X-ray diffractometer (XRD) from Japan. The experimental conditions were 40 kV voltage and 15 mA, with the instrument operating in Cu-Ka target mode. The diffraction data acquisition range was 25–65°, the scan rate was 2–5° / min, and the step size was 0.02. For the main peak position of the samples, repeated scans were performed at more detailed and accurate scan rates and frequencies. The experimental data were then integrated for testing and analysis.

[0056] The surface microstructure and characteristics of the synthesized samples were observed and analyzed using a field emission scanning electron microscope (SEM, SU1510, Hitachi).

[0057] The distribution and content of elements on the surface of the yellow pigment sample were analyzed using X-ray photoelectron spectroscopy (EDS). The synthesized yellow pigment sample was then immersed in anhydrous ethanol and ultrasonically dispersed. The particle size distribution of the powder was measured using a multi-angle high-sensitivity Zeta potential analyzer (Brookhaven Omni), and the microstructure and size of the powder were observed using scanning electron microscopy (SEM) to explain phenomena observed in coatings or practical applications.

[0058] The surface composition and chemical valence state of the samples were analyzed using Thermno Fisher Scientific k-alpha+ X-ray photoelectron spectroscopy (XPS). Monochromatic Al K-α radiation with an energy of 1486.68 eV and a spot size of 400–30 μm was used for analysis. After the samples were completely dried, a small amount was placed on conductive adhesive and then transferred to the sample chamber of the spectrometer for detection.

[0059] The optical properties (including absorption and reflection) of the synthesized samples were analyzed using an Agilent Carrier 5000 UV-Vis-NIR spectrophotometer, and their UV-Vis-NIR diffuse reflectance coefficients were determined. BaSO4 was used as the standard substance in the experiment.

[0060] The average near-infrared solar reflectance R* of the sample in the wavelength range of 700-2500nm can be calculated according to ASTM G173-03, as shown in Formula 1:

[0061]

[0062] In the formula, r(λ) and i(λ) represent the experimentally measured reflectance of 700–2500 nm and the reflectance according to ASTM G173-03 (W·m), respectively. -2 ·nm -1 The solar spectral irradiance obtained.

[0063] The band gap width E of the sample in the 200-800 nm rangeg It is calculated using the following formula 2:

[0064]

[0065] In the above formula, λ represents the absorption threshold in the ultraviolet-visible spectrum. (Figure F(R)) 2 On the y-axis, Eg is on the x-axis, and the tangent line intersecting the x-axis represents the absorption limit of the sample.

[0066] The absorption limit F(R) is calculated using the Kubelka-Munk function, as shown in Equation 3:

[0067]

[0068] In this formula, R represents the reflectance of the synthesized sample in the visible spectrum.

[0069] Under D65 standard illuminant and a 10° observation angle, the colorimetric coordinates of the samples were measured using a CS-580A spectrophotometer (CHN specification), and the color coordinates were determined according to CIE 1931 L. * a * b * Colorimetric space coordinate system representation. L * This indicates the brightness range, with values ​​ranging from 0 to 100. * and b * This represents the chromaticity characteristic of color, where a * The value represents the red and green characteristics of the color, ranging from -128 (green) to +128 (red). * The value represents the yellow and blue characteristics of the color, ranging from -128 (blue) to +128 (yellow). Additionally, the pigment's saturation C... * The formulas for calculating the chromaticity angle H° are formulas 4 and 5:

[0070] C * =[(α * ) 2 +(b * ) 2 ] 1 / 2 (4)

[0071]

[0072] The chemical stability of yellow pigments is tested, primarily by evaluating their resistance to acids, alkalis, and high temperatures. Samples are placed in 5% concentrations of strong acid, strong alkali, and high-temperature environments (e.g., calcination at 1200℃ for 120 minutes) for a period of time, and their colorimetric values ​​ΔE are recorded. * The changes before and after. Use Formula 6 to determine whether the pigment is suitable for actual production applications.

[0073] ΔE * =[(ΔL * ) 2 +(Δa * )+(Δb * ) 2 ] 1 / 2 (6)

[0074] To evaluate the practical application of the prepared samples, they were applied to the surface of an iron house model to test their potential as pigments. The thermal insulation performance of the synthesized samples was characterized using an infrared thermal imager. The prepared pigment sample was mixed with glaze at a 1:1 mass ratio and uniformly coated onto the surface of the iron house model, then air-dried at room temperature. The prepared model and the uncoated model were placed under a 100W infrared lamp, with the model maintained at a distance of 15-20 cm from the mold, and the top temperature was measured using an infrared thermal imager. The air temperature of both types was measured every 2, 5, 8, 10, 15, 20, 30, 60, and 90 minutes using a UT320D thermocouple thermometer.

[0075] Test Example 1

[0076] Figure 1 The yellow pigment Y in Example 1 2-x Bi x XRD patterns of MoO6 (x values ​​of 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3). Figure 1 As can be seen, the main diffraction peaks are strong and sharp, indicating a high degree of crystallinity in the pigment powder. These sharp main peaks indicate a highly ordered crystal structure in the sample, and also reflect the high regularity and periodicity of the atomic arrangement in the crystal.

[0077] Figure 2 The yellow pigment Y in Example 1 1.8 Bi 0.2 A schematic diagram of the crystal structure of MoO6 is shown below. Figure 2 As shown, all doped samples have a monoclinic structure with space group C2 / c(15). α=90°; β=108.5°; γ=90°. combine Figure 1 Compared with the standard PDF card NO.52-0650, it can be seen that the doped yellow pigment does not have the main diffraction peaks of Y2O3, Bi2O3, and MoO3, indicating that Y 2-x Bi x Solid solutions of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) were fully formed with good crystallinity. See also Figure 2As the doping concentration increases, the lattice volume gradually decreases. By increasing 2θ (28.5°–29.4°), a shift of the principal crystal plane to a lower angle can be observed. According to Bragg's law, the characteristic diffraction peaks of the sample will shift after the solid solution forms. In this invention, Y... 3+ Bid 3+ Substitution results in larger ionic radii entering the crystal lattice, causing a certain degree of lattice expansion and a shift of the crystal plane at a small angle (red region). When the Bi(III) doping concentration is 0.3%, the double peak of the main peak disappears. Studies suggest the formation of a peak envelope, indicating a decrease in matching degree and the possible presence of a small amount of unreacted cubic Y₂O₃ phase.

[0078] Test Example 2

[0079] Using field emission scanning electron microscopy (FESEM) to study Y 2-x Bi x The morphology and structure of MoO6 (x = 0-0.3) pigment powder were characterized. Figure 3 The yellow pigment Y in Example 1 2-x Bi x SEM images of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3). From Figure 3 It can be seen that, at the microscopic level, the morphological characteristics of the yellow pigment-doped sample and the undoped sample (i.e., x=0) are similar. The morphology of the samples is irregular, which may be due to the inability to control the morphology of the samples by the high-temperature solid-state synthesis method. Meanwhile, Bi... 3+ Doping can also cause changes in particle size and morphology. As can be seen from the scanning electron microscope images, all samples exhibit a certain degree of agglomeration. The size of the agglomerated particles is not uniform, with a particle size range of approximately 1–30 μm.

[0080] The composition and distribution of elements on the pigment surface were characterized and analyzed using energy dispersive spectroscopy (EDS). Figure 4 The yellow pigment Y in Example 1 1.8 Bi 0.2 EDS plot and elemental distribution map of MoO6. From Figure 4 As can be seen from the image, the synthesized pigment sample is mainly composed of four elements: Y, Mo, Bi, and O. Observing the elemental distribution diagram of the pigment sample shows that each element is uniformly distributed in the crystal lattice, confirming the homogeneity of the sample formation and further indicating that Bi... 3+ In Y 2-x Bi x It is well embedded in MoO6, forming a solid solution.

[0081] Test Example 3

[0082] To further investigate the chemical composition and valence state of the sample, Y1.8 Bi 0.2 MoO6 was used as a typical sample, and XPS characterization was performed. The results are as follows: Figure 5 As shown, Figure 5 For Y 1.8 Bi 0.2 XPS scan full spectrum (a) and fine scan spectrum (be) of MoO6. From Figure 5 The presence of Y, Mo, Bi, and O elements, as well as a small amount of C element, can be observed in a. Figure 5 (a)). Figure 5 (b) shows the main peaks of Y 3d and Bi 4f obtained by XPS analysis, with clearly separated spin-orbit splitting peaks in the Y 3d region. The spectra show that the two peaks with binding energies of 158.9 eV and 156.9 eV correspond to the Y 3d region, respectively. 3 / 2 and 3D 5 / 2 Similarly, Bi also exhibits distinct spin-orbit splitting peaks, with two peaks at binding energies of 164.1 eV and 158.7 eV corresponding to Bi 4f, respectively. 5 / 2 and 4f 7 / 2 These two peaks are Bi 3+ The characteristic peaks of the oxidation state are consistent with the splitting peaks of the oxidized Bi element. This proves that Y and Bi elements exist in the +3 oxidation state in the synthesized sample. Figure 5 (c) It can be seen that the XPS spectrum of O1s can be divided into two peaks, among which the peak with a binding energy of 532.7 eV belongs to chemisorbed oxygen (O2). A The peak with a binding energy of 530.4 eV belongs to lattice oxygen (O). L The peak areas show that oxygen mainly exists in the compound as lattice oxygen. This is because oxygen exists in the sample not only as lattice oxygen (O₂). L It exists in the form of ) and also in small amounts of chemisorbed oxygen (O A It exists in the form of ), and XPS data analysis shows that oxygen vacancies (O) are almost non-existent. V The presence of oxygen is consistent with XPS spectral data analysis of other lattice compositions (Y, Mo, Bi). Figure 5 (d) In the XPS spectrum of Mo 3d, obvious spin-orbit splitting peaks can be observed in the Mo 3d region. The two peaks with binding energies of 232.5 eV and 235.7 eV correspond to the Mo 3d region, respectively. 5 / 2 and 3D 2 / 3 , is Mo 6+ Characteristic peaks of the oxidation state. The above results indicate that Bi ions were successfully doped into the Y₂MoO₆ matrix lattice, forming a new solid solution.

[0083] Test Example 4

[0084] The surface smoothness of a pigment is closely related to the particle size distribution of the pigment particles. Figure 6 The yellow pigment Y in Example 1 2-x Bi x Particle size distribution of MoO6 (x values ​​are 0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3). From... Figure 6 It can be seen that the particle size of the pigment samples is mainly distributed around 1 μm, and the distribution is relatively uniform. By observing the changes in D50 of the pigment powder under different doping concentrations, it can be seen that the particle size of the yellow pigment of this invention (i.e., x = 0.05, 0.1, 0.15, 0.2, and 0.25) also increases with the increase of doping element. This result is consistent with the results obtained by SEM, further confirming the observation and analysis of particle size distribution. The particle size distribution range of the pigment sample powder of this invention is relatively small, exhibiting a good particle size distribution, which is beneficial to the preparation of pigment sample coatings.

[0085] Test Example 5

[0086] Color is considered one of the most important properties of pigment powders. Figure 7 The yellow pigment Y in Example 1 2-x Bi x Absorption spectra of MoO6 (x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3). From... Figure 7 As can be seen, there is no obvious absorption peak in the wavelength range of 550–780 nm. This is mainly due to the doping of bismuth into the yttrium molybdate lattice, which produces d-band transitions. Its electrons transition from one energy level to another, absorbing light of a specific wavelength, thus resulting in a broad absorption band (300–580 nm wavelength range) observed across the entire spectrum. Since the wavelength around 600 nm corresponds to yellow light in the visible light range, this is the source of the yellow hue of objects.

[0087] Reflection in the visible light region determines the color characteristics of the powder. This invention uses the Kubelka-Munk (KM) formula to calculate the color of Y under different doping concentrations. 2-x Bi x Band gap curves of MoO6 (x = 0-0.3) pigment powder. Figure 8 The yellow pigment Y in Example 1 2-x Bi x Absorption limit diagrams for MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3); as shown Figure 8 As shown, with hv as the x-axis, F(R) 2 Using the ordinate as the x-axis, plot the curve according to Formula 3. The intersection of the tangent line to the curve and the x-axis represents the band gap width. For example... Figure 8 As shown, the E of the undoped sample gThe value is approximately 3.27 eV. With Bi 3+ With increasing doping concentration, the E of the sample g The value rapidly contracted to below 3 eV and continued to contract slowly. With Bi 3+ As the doping concentration increases, the absorption edge color redshifts, the band gap shrinks, and this shift is inversely proportional to the increase in doping concentration. This pattern is consistent with the color changes observed in the pigment samples. According to band structure theory, the corresponding energy range in the visible light region is 1.8–3.1 eV, while the near-infrared radiation energy range is 0.5–1.8 eV. Figure 8 As can be seen, the band gaps of all the finished products are not in the near-infrared range (0.5-1.8 eV). Based on band structure theory, this sample exhibits a high energy level in the near-infrared band, thus possessing a high energy level across the entire wavelength range. Due to its weak absorption, the synthetic pigment has a high near-infrared reflectance.

[0088] Test Example 6

[0089] Figure 9 The yellow pigment Y in Example 1 2-x Bi x L of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 respectively) * a * b * Values. Table 1 shows... Figure 8 Specific L * a * b * C * H° value table. Figure 9 As can be seen from Table 1, the L of the pigment * The value reaches its maximum at x = 0 (i.e., no doping with ions), at 96.41. At this point, the pigment sample appears white. With the increase of Bi... 3+ With increasing doping concentration, the pigment exhibits a yellow hue, and the brightness value decreases as the doping concentration increases. This phenomenon is due to the presence of other elements doped into the unit cells of the sample powder, affecting the absorption and reflection of light at different wavelengths, thus causing a change in the sample's color. This is consistent with the trend observed in previous calculations of the band gap width of samples with different doping concentrations. Among all samples with a gradient of doped ion content, it was found that the doping elements significantly altered the sample color, changing it from white to yellow, and b * The value increases significantly with increasing doping concentration. When the doping concentration reaches approximately 0.2%, the sample's b... * The value gradually stabilized. There was no obvious upward trend, and eventually b... * The value reaches around 50, which meets the color requirements of the pigment.

[0090] Table 1. Y 2-x Bi xChromaticity coordinates of MoO6 (x = 0-0.3) synthetic pigment

[0091]

[0092] To further visualize the color characteristics of the synthetic samples, the internationally recognized CIE 1931 color space system was used for visual evaluation. Figure 10 The yellow pigment Y in Example 1 2-x Bi x The CIE 1931 chromaticity coordinates of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) are shown below. Figure 10 It can be seen that all samples from this invention are concentrated in the yellow area, exhibiting a progressive distribution. This indicates that the color change of the dopant elements is primarily yellow. Figure 11 The yellow pigment Y in Example 1 2-x Bi x Physical images of MoO6 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3 respectively), from... Figure 11 It can also be clearly seen that as the amount of dopant increases, the yellow-green hue value gradually increases, which is consistent with previous measurement data. By using dopant elements, the color of synthetic pigments can be effectively adjusted to give them a rich variety of yellow hues, thereby meeting the market demand for pigments with different color properties.

[0093] Test Example 7

[0094] The near-infrared reflectance properties of high near-infrared reflectance pigments can be evaluated using near-infrared reflectance. To study Y... 2-x Bi x The near-infrared reflectance characteristics of MoO6 (x = 0-0.3) pigment were investigated, and its reflectance in the range of 700-2500 nm was measured. Figure 12 The yellow pigment Y in Example 1 2-x Bi x The average reflectance of the near-infrared reflectance spectrum (a) and the average reflectance of the near-infrared solar reflectance spectrum (b) of MoO6 (x = 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3, respectively); Figure 12 As shown in (a), it can be seen from the figure that Bi doping has a certain impact on the near-infrared reflectance performance of the sample. With the increase of doping concentration, NIR reflectance first increases and then decreases, reaching a maximum value when the doping concentration x = 0.2. This may be due to the regulation of the crystal structure by the Bi element in the lattice. The reflectance of the pigment at 1100 nm is considered one of the most important indicators for evaluating the reflectance performance of the near-infrared spectrum because it is located at the boundary between the short-wavelength and long-wavelength regions. Table 2 shows the yellow pigment Y in Example 1. 2-x Bix The reflectance at 1100 nm, average reflectance R% of the near-infrared reflectance spectrum, and average reflectance R*% of the near-infrared solar reflectance spectrum of MoO6 pigments (x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) are shown in Table 2. The synthetic pigments exhibit higher reflectance and average reflectance R% at 1100 nm than the substrate Y2MoO6 (i.e., x = 0). The near-infrared solar reflectance curves of the pigment samples were calculated according to ASTM G173-03 standard. Figure 12 As shown in (b), the maximum R* value of the yellow pigment of the present invention reaches 103.49%. The results indicate that bismuth doping not only gives the pigment a higher near-infrared solar average reflectance, but also a deeper yellow color.

[0095] Table 2Y 2-x Bi x Reflectance at 1100 nm, average near-infrared reflectance R%, and average near-infrared solar reflectance R*% of MoO6 (x = 0-0.3) pigments.

[0096]

[0097]

[0098] Test Example 8

[0099] Infrared thermal imaging studies can more directly reflect the infrared reflectivity of pigments in practical applications. This invention will use Y... 1.8 Bi 0.2 MoO6 sample and alkyd resin (adhesive) were mixed uniformly at a weight ratio of 1:1. A small amount of white glaze and defoamer were then added and mixed thoroughly. This mixture was then applied to a house model, serving as the experimental group. The control group consisted of an uncoated iron house model. The ambient temperature was room temperature, with air circulation maintained to ensure both models had the same initial temperature. Thermocouple thermometers were used to simulate the temperature inside the "house" model, where T1 and T2 represent the temperatures of the experimental and control models, respectively, with the temperature difference ΔT = T2 - T1. The experimental results are as follows: Figure 13 As shown. Figure 13 For Y in test example 8 1.8 Bi 0.2 The internal temperatures of the MoO6-coated model (experimental group) and the uncoated model (control group) at different time points, from Figure 13It can be seen that throughout the irradiation process, the internal temperature of the coated model remained lower than that of the uncoated model. At the beginning of irradiation, the temperature difference between the two models was small. As the irradiation time increased, the temperature difference between the two models increased significantly. After more than 20 minutes, the rate of increase in temperature difference slowed down, and the temperature difference between the two models reached 7°C. When the irradiation time reached 60 minutes, the temperature difference remained at 7.4°C. Based on the final experiment after 90 minutes, the temperature difference remained at 7.4°C. The surface temperature of the blank model reached a maximum of 46.1°C, while the surface temperature of the model coated with pigment eventually stabilized at around 39°C. This means that the pigment of this invention has a high near-infrared reflectivity, which can reflect most of the heat under illumination, effectively reducing the internal temperature of the house model, thereby reducing energy consumption and improving the comfort of the house.

[0100] Test Example 9

[0101] For Y 1.8 Bi 0.2 MoO6 was subjected to a tolerance test, the specific process of which is as follows:

[0102] (1) The synthesized pigment sample Y 1.8 Bi 0.2 MoO6 was soaked in ammonia, sodium hydroxide solution, 5% nitric acid solution, sulfuric acid, HCl, and deionized water for 8 hours each. The synthesized pigments were then filtered, washed, and dried, and the color values ​​of the pigment samples after soaking were recorded.

[0103] (2) The synthesized pigment Y 1.8 Bi 0.2 MoO6 was calcined in a muffle furnace at 1200℃ for 120 minutes, and the changes in chromaticity values ​​before and after calcination were recorded.

[0104] The product of Test Example 9, after being calcined at 1200°C, was then calcined again at 1200°C for 120 minutes to simulate its high-temperature stability.

[0105] When ΔE * When ΔE ≤ 1, it indicates that the pigment shows almost no visual change and is difficult to detect with the naked eye. * ≤5 indicates that the color can be maintained even after soaking in acid, alkali, or aqueous solution.

[0106] The test results are shown in Table 3 below. The colorimetric value ΔE of the pigment of this invention is as follows. * Changes in ΔE under acidic / alkaline and high-temperature environments * <5, demonstrating that the synthesized pigment exhibits good chemical stability under high temperature, acidic, and alkaline conditions. In practical applications, it helps improve the acid and alkali resistance and high temperature resistance of materials.

[0107] Table 3. Changes in chromaticity values ​​of synthetic pigments before and after the colorfastness test.

[0108]

[0109] In Table 3, "1200℃" means that the product of Test Example 9, after being calcined at 1200℃, is calcined again at 1200℃ for 120 minutes to simulate its high-temperature stability.

[0110] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A yellow pigment, characterized in that, The general formula for the yellow pigment is Y. 2-x Bi x MoO6, in which: Bi is the doping element, x represents the molar amount of Bi doping, and 0 < x < 0.

3.

2. The yellow pigment according to claim 1, characterized in that, The yellow pigment has a crystalline structure, which is monoclinic and has a space group of C2 / c(15).

3. The yellow pigment according to claim 1, characterized in that, The average particle size of the yellow pigment is 1–30 μm.

4. The yellow pigment according to claim 1, characterized in that, The average reflectance of the near-infrared reflectance spectrum of the yellow pigment is not less than 104%; Preferably, the near-infrared reflectance of the yellow pigment is 99% to 103% at a wavelength of 1100 nm.

5. The method for preparing the yellow pigment according to any one of claims 1-4, characterized in that, The method is as follows: Using Y, Bi, and Mo sources as raw materials, according to the chemical formula Y 2-x Bi x The yellow pigment is obtained by mixing the elements in MoO6 according to their stoichiometric ratios and then sintering them in a solid state.

6. The method according to claim 5, characterized in that, The Y source is provided by a compound containing Y; for example, by at least one of carbonates, oxides, chlorides, nitrates and sulfates containing Y; preferably by an oxide containing Y (e.g., Y₂O₃). Preferably, the Bi source is provided by a Bi-containing compound. For example, it is provided by at least one of Bi-containing carbonates, oxides, chlorides, nitrates, and sulfates; more preferably, it is provided by a Bi-containing oxide (e.g., Bi₂O₃).

7. The method according to claim 5, characterized in that, The Mo source is provided by a Mo-containing compound; for example, by at least one of a Mo-containing carbonate, oxide, chloride, nitrate, and sulfate; preferably by a Mo-containing oxide (e.g., MoO3).

8. The method according to claim 5, characterized in that, The solid-state sintering temperature is 400℃~1300℃, and the solid-state sintering time is 4-10h.

9. The method according to claim 5, characterized in that, The solid-state sintering process involves first holding the material at 400–550℃ for 1–3 hours, and then holding it at 550–1300℃ for 4–10 hours.

10. The use of the yellow pigment according to any one of claims 1-4 in the fields of building materials, coatings, plastics, vehicles, ship decks, aerospace, oil tanks or inks.

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