Terbium-doped zirconium germanate-based orange pigment as well as preparation method and application thereof

Abstract

The invention relates to a zirconium germanate-based orange pigment as well as a preparation method and application thereof. The pigment matrix is zirconium germanate, a doping element contains Tb, the chemical composition of the pigment is Zr < 1-x > Tb < x > GeO4, and x is equal to 0.05-0.3. The preparation method comprises a sol-gel method, a coprecipitation method or a solid-phase synthesis method. The pigment can be used as an orange pigment to be applied to the fields of plastics, coatings, enamel, ceramics or glass. The zirconium germanate-based orange pigment provided by the invention is non-toxic, good in stability and bright in color.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inorganic pigments, in particular to a zirconium germanate-based orange pigment, a preparation method and application thereof. BACKGROUND

[0002] With the development of modern industry, inorganic pigments are increasingly widely used in the fields of plastics, coatings, enamel, ceramics and glass, etc. Among them, orange pigments have always been a research hotspot due to their bright color and wide application prospects. However, the commonly used orange pigments on the market mainly include cadmium sulfide and cadmium selenide (CdS 1～x Se x ), lead chromate (PbCrO4), iron oxide orange (α-Fe2O3), etc. These traditional pigments have many problems, such as containing toxic heavy metals, poor thermal stability, weak tinting strength, etc., which limit their use in high-temperature application fields.

[0003] In recent years, zirconium-based pigments have gradually become an important direction of inorganic pigment research due to their excellent thermal stability, chemical stability and environmental protection characteristics. Zirconium silicate-based pigments, as a typical representative of zirconium-based pigments, have been widely used in the field of ceramics. Related technologies disclose a method for preparing zirconium silicate-based ceramic pigments by a non-hydrolytic sol-gel process. The method uses anhydrous zirconium source and anhydrous silicon source as precursors, and through reflux or bomb process, a zirconium silicate sol uniformly mixed with coloring substances is prepared, and after drying and heat treatment, a zirconium silicate-based ceramic pigment is obtained. This method has the advantages of high synthesis rate and low synthesis temperature, but still has the problems of complex process and high cost.

[0004] In order to solve the dispersion and particle size control problems in the preparation process of traditional pigments, related technologies propose a method for preparing in-situ generated carbon black wrapped pigments by a non-hydrolytic sol-gel method. By adding an organic compound capable of generating carbon black in-situ to the precursor mixed solution, zirconium silicate gel is formed through condensation reflux and bomb treatment, and finally zirconium silicate-based carbon black wrapped pigments are obtained. Although this method simplifies the preparation process, it still cannot meet the needs of high-temperature applications.

[0005] In terms of improving the stability of pigments, related technologies disclose a crystalline silica wrapped γ-Ce2S3 red pigment and a preparation method thereof. The pigment is prepared by acid and alkali step-by-step catalytic sol-gel method, and the wrapped pigment has excellent acid corrosion resistance and high-temperature oxidation resistance. The method is simple to operate and has high wrapping efficiency, but it mainly targets red pigments, and the research on orange pigments is relatively less.

[0006] The related technology proposes a preparation method of Mn ion doped zirconium silicate black colorant prepared by non-hydrolytic sol-gel method, which is prepared by dissolving zirconium source, silicon source and manganese source in non-aqueous solvent, mixing and stirring, and then refluxing in an oil bath to obtain a manganese-containing zirconium silicate precursor wet gel, and then a series of treatments are performed to obtain the Mn ion doped zirconium silicate black colorant. The colorant prepared by the method has excellent color rendering performance and environmental friendliness, but mainly focuses on the research of black colorant.

[0007] Recently, the related technology discloses a preparation method of zirconium silicate-based wrapped colorant prepared by non-aqueous precipitation method, which is prepared by forming a zirconium silicate sol through non-hydrolytic polycondensation reaction, and then mixing with a colorant powder to form a suspension, and then a series of treatments are performed to obtain the zirconium silicate-based wrapped colorant. The method has wide practical range and the solvent can be recycled, but the application research in the field of orange colorant is still insufficient.

[0008] In summary, the existing orange colorants mainly have the following problems: (1) traditional orange colorants such as cadmium sulfide (CdS 1～x Se x ) and lead chromate (PbCrO4) contain toxic heavy metal elements, which not only pollute the environment, but also pose a threat to human health; (2) the synthesis process of some orange colorants such as tin-zinc-titanium composite oxide (Sn 2～x Zn X Ti 2～y Nb y O 7～δ ) is complex and the production cost is high; (3) the existing orange colorants such as CdS 1～x Se x and PbCrO4 have poor thermal stability and are easily decomposed or discolored at high temperatures, which limits their use in high-temperature application fields; (4) some orange colorants such as iron oxide orange (α-Fe2O3) have weak color strength and low color saturation, which is difficult to meet the needs of high-end applications.

[0009] Therefore, it is of great practical significance to develop an environmentally friendly, high-stability and high-color-strength orange colorant. SUMMARY

[0010] The technical problem to be solved by the present application is to provide a zirconium germanate doped terbium orange inorganic colorant which is environmentally friendly, non-toxic, has good photo-thermal stability, excellent color rendering performance and strong coloration ability, in view of the defects of existing high-performance inorganic orange colorants, such as containing toxic heavy metals, complex synthesis process, poor photo-thermal stability, weak color strength and low color saturation.

[0011] The technical scheme adopted by the present application to solve the technical problem is to provide a zirconium germanate-based orange colorant, wherein the zirconium germanate-based orange colorant matrix is zirconium germanate, and the doping element contains Tb, and the chemical composition is Zr 1～x Tbx GeO4, wherein x = 0.05-0.3.

[0012] Zirconium germanate is an inorganic compound belonging to the tetragonal system. In the crystal structure, zirconium atoms are bonded to germanium atoms through oxygen atoms. This structure makes zirconium germanate have good chemical stability and thermal stability, and its melting point is also relatively high, usually above 1200℃, so it has good chemical stability at room temperature and is not easy to react with other substances. As a colorant matrix, it has good chemical stability. In addition, compared with zirconium silicate, zirconium germanate has a larger lattice parameter and a more relaxed crystal field environment, which makes it more stable to accommodate color-developing ions that are difficult to stabilize or have poor color development in zirconium silicate.

[0013] The rare earth element Tb as a doping element forms LMCT (charge transfer between ligand and metal) with the substrate zirconium germanate, which has strong light absorption performance, and significantly enhances the light absorption of the strong absorption region.

[0014] It should be noted that the doping element can also include europium or cerium. When the doping element further includes europium or cerium, the luminescent performance of the colorant can be further regulated. The doping of europium enhances the emission in the red region, and the doping of cerium improves the absorption efficiency in the ultraviolet region.

[0015] The present application uses ZrGeO4 matrix as a colorant carrier, and uses the doping of rare earth ion Tb 3+ as a color center, which forms LMCT (charge transfer between ligand and metal) with the substrate zirconium germanate, which has strong light absorption performance, and significantly enhances the light absorption.

[0016] A further technical solution of the present application is that the zirconium germanate-based orange colorant Zr 1～x Tb x GeO4, wherein x = 0.1-0.15.

[0017] The present application also provides a preparation method of a zirconium germanate-based orange colorant, which can be one of a sol-gel method, a coprecipitation method or a solid-phase synthesis method.

[0018] A further technical solution of the present application is that the sol-gel method comprises the following steps: adding a zirconium source, a germanium source and a terbium source into acid in a certain proportion to make them fully dissolved to obtain a first mixture; adding propylene oxide (PO) or citric acid (Ce) into the first mixture and stirring until a sol is formed; evaporating and drying the water in the sol, and then grinding into a powder; adding the powder into a certain amount of mineralizer and mixing uniformly, and then sintering to obtain a sintered body; grinding the sintered body, washing and drying to obtain the zirconium germanate-based orange colorant.

[0019] A further technical solution of the present application is that the co-precipitation method comprises the following steps: adding a zirconium source, a germanium source and a terbium source into acid in a certain proportion to fully dissolve to obtain a second mixture; adding ammonia water to adjust the pH of the second mixture to above 9.5 to obtain an alkaline solution; centrifuging the alkaline solution after standing to obtain a precipitate; drying the precipitate and adding a certain amount of mineralizer to sinter to obtain a sintered body; grinding the sintered body, washing and drying to obtain the zirconium germanate-based orange pigment.

[0020] A further technical solution of the present application is that the solid-phase synthesis method comprises the following steps: mixing zirconium oxide, germanium oxide, terbium oxide and a mineralizer in a certain proportion to obtain a third mixture; sintering the third mixture for a period of time to obtain a third sintered body; grinding the third sintered body, washing and drying to obtain a zirconium germanate-based orange pigment.

[0021] A further technical solution of the present application is that the zirconium source can be one of zirconium oxychloride octahydrate, zirconium chloride, zirconium n-propyl alcohol, zirconium oxide and zirconium sulfate tetrahydrate; the germanium source can be one of germanium oxide, germanate, germanium tetrachloride and germanium powder; and the terbium source can be one of terbium chloride hexahydrate, terbium oxide and terbium nitrate hexahydrate.

[0022] It should be noted that the specific form of the zirconium source, the germanium source and the terbium source is not limited, as long as they can form a sol in an acidic solution or form a precipitate in an alkaline solution containing zirconium, germanium and terbium.

[0023] A further technical solution of the present application is that the mineralizer can be one or more of LiF, NaF and NH3F, and preferably the mineralizer is LiF.

[0024] The addition of the mineralizer can obtain a better matrix crystallinity and a higher chroma value. The addition of the LiF mineralizer can reduce the sintering temperature of the material, promote the growth of the zirconium germanate crystal and the effective doping of the terbium ion, improve the crystallinity and particle morphology of the material, and finally make the prepared orange pigment have higher luminous intensity, more pure color tone and better thermal stability.

[0025] A further technical solution of the present application is that the sintering temperature is 850-1200°C, and the sintering time is 1-8 hours.

[0026] It should be noted that the final sintering temperature and sintering time are different for different preparation methods, and of course the sintering temperature and sintering time are related to each other, and the sintering temperature and sintering time can also be reduced by adding a mineralizer to improve the production efficiency.

[0027] The present application also provides a use of the zirconium germanate-based orange pigment, which is applied to the fields of plastics, coatings, enamel, ceramics or glass as an orange pigment.

[0028] The present application has the advantages of:

[0029] 1) Environmentally friendly and non-toxic: The zirconium germanate-based orange colorant of the present application does not contain toxic heavy metal elements such as cadmium, lead, chromium, etc., and does not produce toxic substances during production, meeting environmental protection requirements and solving the problem of toxic elements in traditional cadmium sulfide (CdS 1～x Se x ) and lead chromate (PbCrO4) and other colorants;

[0030] 2) Good light and thermal stability: The zirconium germanate-based orange colorant of the present application maintains a single zirconium germanate phase after sintering at a high temperature of 850℃ to 1200℃, has excellent thermal stability, and is significantly better than traditional CdS 1～x Se x , PbCrO4 and BiVO4 and other colorants;

[0031] 3) Excellent color development performance: Through the design of LMCT, 15% to 25% of blue-violet light below 520nm is efficiently absorbed (the transition zone is 500nm to 650nm), and 620nm to 720nm orange-red light is a high reflection zone, with a reflection of up to 75% to 90%, so that the colorant presents a bright orange color (L*a*b* values are 50 to 90, 10 to 30, and 25 to 60, respectively);

[0032] 4) Strong coloring ability: The present application greatly increases the absorption intensity through the LMCT mechanism, has a stronger absorption intensity than traditional d-d transition and f-f transition, thereby resulting in better coloring ability and solving the problem of low color saturation of traditional iron oxide orange (α-Fe2O3);

[0033] 5) Simple process: The present application provides three preparation methods (sol-gel method, coprecipitation method and solid phase method), which are simpler than the complex synthesis process of traditional tin-zinc-titanium composite oxides (Sn 2～x Zn X Ti 2～y Nb y O 7～δ ). BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a physical map of the zirconium germanate-based orange colorant prepared by the sol-gel method (PO);

[0035] Figure 2 is an XRD graph of the zirconium germanate-based orange colorant prepared by the sol-gel method (PO);

[0036] Figure 3 is a diffuse reflectance spectrum of the zirconium germanate-based orange colorant prepared by the sol-gel method (PO);

[0037] Figure 4 XRD pattern of ZrGeO4-based orange colorant prepared by sol-gel method with citric acid (Ce) ;

[0038] Figure 5 Diffuse reflectance spectrum of ZrGeO4-based orange colorant prepared by sol-gel method with citric acid (Ce) ;

[0039] Figure 6 XRD pattern of ZrGeO4-based orange colorant prepared by co-precipitation method;

[0040] Figure 7 Diffuse reflectance spectrum of ZrGeO4-based orange colorant prepared by co-precipitation method;

[0041] Figure 8 Diffuse reflectance spectrum of ZrGeO4-based orange colorant prepared by solid phase method. DETAILED DESCRIPTION

[0042] The application will be described in further detail below with reference to the drawings, so that those skilled in the art can better understand the application and implement it.

[0043] In the present application, all the raw materials for preparation are preferably commercially available products well known to those skilled in the art, and the water is preferably deionized water, unless otherwise specified.

[0044] The principle of coloring by inorganic colorants is mainly to present color by absorbing and reflecting specific wavelengths of light. These pigments are dispersed in a medium, when light irradiates the surface of the pigment, the pigment will absorb part of the wavelength of light, and reflect other wavelengths of light, so that people see the color determined by the reflected light wavelength. Different inorganic colorants absorb and reflect different wavelengths of light, thus presenting different colors. Their color change depends on the atomic structure and the nature of chemical bonds. The existing synthetic colorants mainly have d-d transition and f-f transition and ligand to metal charge transfer (LMCT), and LMCT has stronger absorption intensity than d-d transition and f-f transition, thus resulting in better coloring ability. The present application uses the doping element Tb as a chromophore, and uses the electron transfer on O2p to Tb4f to present orange. Or by co-doping Tb with europium and cerium to regulate the absorption band and reflection band of ZrGeO4 to the light, so that ZrGeO4 can present orange color. 1～x Tb x GeO4 presents orange color.

[0045] The present application provides a ZrGeO4-based orange colorant, the matrix of which is ZrGeO4, and the doping element contains Tb. The chemical composition of the ZrGeO4-based orange colorant is ZrGeO4, wherein x = 0.05-0.3. 1～x Tb x GeO4, wherein x = 0.05-0.3.

[0046] It should be noted that the value of x represents the content of the doping element Tb, because Tb is the coloring center, therefore the content of Tb cannot be too low, otherwise its coloring ability is poor, which is reflected on the colorant as a lighter orange color, with the increase of the content of Tb, the absorption is enhanced to obtain a deeper orange color, but if the amount of Tb added is too high, it leads to that Tb cannot completely participate in the zirconium germanate, introducing a heterogeneous phase Tb or its oxide, thereby affecting the coloring ability.

[0047] That is, the chemical composition of the zirconium germanate-based orange colorant can be Zr 0.95 Tb 0.05 GeO4, Zr 0.9 Tb 0.1 GeO4, Zr 0.8 Tb 0.2 GeO4, Zr 0.7 Tb 0.3 GeO4, preferably Zr 0.9 Tb 0.1 GeO4.

[0048] In some embodiments, the chemical composition of the zirconium germanate-based orange colorant Zr 1～x Tb x GeO4, wherein x = 0.1-0.15.

[0049] In some embodiments, the zirconium germanate-based orange colorant can be prepared by a sol-gel method, a coprecipitation method or a solid-phase synthesis method.

[0050] The sol-gel method is to use a compound containing a highly chemically active component as a precursor, uniformly mix these raw materials in a liquid phase, and perform hydrolysis and condensation chemical reactions to form a stable transparent sol system in the solution. The sol is slowly polymerized between the gel particles during aging to form a three-dimensional network structure of the gel, and the gel network is filled with a solvent that has lost fluidity, forming a gel. The gel is dried, sintered and solidified to prepare a molecular or even nano-substructure material. Because the raw materials used in the sol-gel method are first dispersed into a solvent to form a low-viscosity solution, molecular-level uniformity can be obtained in a very short time, and the reactants are likely to be uniformly mixed at the molecular level when the gel is formed. Because of the solution reaction step, it is easy to uniformly and quantitatively incorporate some trace elements to achieve uniform doping at the molecular level.

[0051] The coprecipitation method refers to the presence of two or more cations in the solution, which exist in the solution in a homogeneous phase. After adding a precipitant, a uniform precipitate of various components can be obtained through a precipitation reaction. It is an important method for preparing composite oxide ultrafine powders containing two or more metal elements. It has the advantages of simple preparation process, low cost, easy control of preparation conditions, short synthesis period, etc.

[0052] Solid state synthesis is a chemical synthesis method that new phase is generated by interfacial diffusion reaction of solid raw materials under high temperature. The core mechanism is that metal ions migrate through product layer to achieve mass transfer after the interface is formed by powder contact, and the concentration of crystal defects (such as oxygen vacancies) increases with the increase of temperature, which significantly affects the diffusion rate. As a classical method of inorganic material synthesis, its process route is simple and suitable for large-scale production.

[0053] The following will introduce the three preparation methods respectively:

[0054] I. Sol-gel method for preparing zirconium germanate-based orange pigments:

[0055] S1: raw material dissolution: dissolve the zirconium source (such as zirconium oxychloride), germanium source (such as germanium dioxide), terbium source (such as terbium oxide) according to the stoichiometric ratio Zr 1～x Tb x GeO4 into an acid solution, and stir at 60-80°C for 3-5 hours to make it fully dissolved to obtain a first mixture;

[0056] S2: sol formation: add propylene oxide (PO) or citric acid drop by drop into the first mixture while stirring until the pH value of the mixture increases to 5-6, forming a transparent sol;

[0057] S3: drying treatment: evaporate water from the formed sol in a water bath at 80-100°C, and then dry in an oven at 120-150°C for 8-12 hours, and grind the dried gel into powder;

[0058] S4: sintering treatment: mix the powder with 5-10wt% mineralizer uniformly, put it into an alumina crucible, and sinter at 850-1200°C for 1-8 hours to obtain a sintered body;

[0059] S5: post-treatment: grind the sintered body and wash it with deionized water or acid multiple times to remove the residual mineralizer, and dry to obtain a zirconium germanate-based orange pigment.

[0060] It should be noted that the acid solution can be hydrochloric acid or nitric acid or other acids, as long as it can dissolve the germanium source (such as germanium dioxide). The purpose of stirring at 60-80℃ for 3-5 hours is to fully dissolve the raw materials to form a uniform solution, and to ensure that the components are in stoichiometric proportion. Here, stirring can be water bath stirring, magnetic stirring, or other stirring. The addition of propylene oxide (PO) or citric acid is to ensure that the solution forms a sol, preferably propylene oxide, which is a small molecule containing a three-membered epoxy ring. Propylene oxide is unstable and prone to ring-opening reaction. The three-membered ring of propylene oxide opens under certain conditions, first polymerizing into longer polyether chains (linear molecules), and as the reaction proceeds, further cross-linking occurs between molecular chains, forming a three-dimensional network polymer skeleton. The carboxyl group of citric acid reacts with the hydroxyl group / amino group of other molecules to form an ester or amide, like a "bridge" that connects linear molecules into a three-dimensional network structure. After the sol is formed, it still contains a lot of water, which can be further dried. In the present application, the drying temperature is preferably 120-150℃; the time is preferably 8-12h. In the present application, the dried powder is preferably ground to obtain a precursor powder.

[0061] After obtaining the precursor powder, the present application sintering treatment is carried out on the precursor powder to obtain a zirconium germanate-based sintered body. In the present application, the precursor powder is mixed with a mineralizer, preferably LiF, more preferably the content of lithium mineralizer is 5-10wt% of the mass percentage of the powder. Then the precursor powder and the mineralizer mixed powder are sintered to obtain a sintered body, preferably the sintering temperature is 850-1200℃, and the sintering time is 1-8 hours.

[0062] After obtaining the sintered body, the sintered body is ground and washed to remove impurities to obtain a zirconium germanate-based orange pigment. The present application does not have special limitations on the grinding method, and the grinding method known to those skilled in the art can be used. In the present application, the washing preferably includes acid washing and washing in sequence.

[0063] II. Preparation of zirconium germanate-based orange pigment by co-precipitation method:

[0064] S1: raw material dissolution: the zirconium source (such as zirconium oxychloride), germanium source (such as germanium dioxide), terbium source (such as terbium oxide) are added in stoichiometric ratio Zr 1～x Tb x GeO4 is added to hydrochloric acid or nitric acid, and stirred at 60-80℃ for 3-5 hours to fully dissolve and obtain a second mixture;

[0065] S2: precipitation formation: under continuous stirring, slowly add an alkali solution such as ammonia or sodium hydroxide solution to the second mixture until the pH value reaches 9.5 or above, and continue stirring until a uniform alkaline solution is formed;

[0066] S3: Precipitate collection: The alkaline solution is left to stand for 2-4 hours, then centrifugal separation is performed at a speed of 5000-8000 rpm, the precipitate is collected, and washed with deionized water for 3-5 times;

[0067] S4: Sintering treatment: The precipitate is dried at 120°C for 8-12 hours, then mixed uniformly with 5-10 wt% of a mineralizer, and sintered at 850-1100°C for 2-8 hours to obtain a sintered body;

[0068] S5: Post-treatment: The sintered body is ground and washed with deionized water or acid multiple times to remove residual mineralizers, and dried to obtain a zirconium germanate-based orange pigment.

[0069] It should be noted that an alkali solution needs to be added during the formation of the precipitate until the pH value reaches 9.5 or above. Here, a pH of 9.5 or above can ensure the formation of the precipitate. If the pH is below 9.5, the precipitate cannot be formed. Preferably, the pH is between 9.5 and 12. If the pH is too high at 12, the number of washing times in the post-treatment process will be increased. The sintering process and the post-treatment process are the same as the sol-gel method, and will not be described again here.

[0070] III. Preparation of a zirconium germanate-based orange pigment by a solid-phase synthesis method:

[0071] S1: Raw material mixing: Zirconium oxide (ZrO2), germanium oxide (GeO2), and terbium oxide (Tb4O7) are weighed according to the stoichiometric ratio Zr1-xTbxGeO4, 5-10 wt% of a mineralizer is added, and grinding and mixing are performed for 30-60 minutes to obtain a third mixture;

[0072] S2: Sintering treatment: The third mixture is sintered at 1000-1200°C for 6-8 hours to obtain a third sintered body;

[0073] S3: Post-treatment: The third sintered body is ground and washed with deionized water multiple times to remove residual mineralizers, and dried at 80°C for 8-12 hours to obtain a zirconium germanate-based orange pigment.

[0074] It should be noted that in the sintering treatment of the solid-phase synthesis method, the sintering time is preferably 6-10 hours, which is longer than the time in the sol-gel method and the coprecipitation method. This is to ensure that the atoms are fully diffused, so that the doping elements can enter the crystal structure of the matrix.

[0075] In some embodiments, the mineralizer can be one or more of LiF, NaF, and NH3F, and the preferred mineralizer is LiF.

[0076] The mineralizer can accelerate the reaction process, promote the decomposition of the precursor and the formation of intermediates, reduce the reaction temperature, and promote the formation of ceramic crystalline compounds.

[0077] In some embodiments, the zirconium source comprises one of zirconium octahydrate oxychloride, zirconium chloride, zirconium n-propylate, zirconium oxide, zirconium sulfate tetrahydrate; the germanium source comprises one of germanium oxide, germanate, germanium tetrachloride, germanium powder; the terbium source comprises one of terbium chloride hexahydrate, terbium oxide, terbium nitrate hexahydrate.

[0078] It should be noted that the above raw materials can all be used to prepare the zirconium germanate-based orange colorant. However, when different raw materials are used, the dissolution conditions need to be adjusted accordingly. For example, when zirconium oxide is used as the zirconium source, it needs to be dissolved at a higher temperature (about 70°C) for a longer time (about 3 hours); when germanium powder is used as the germanium source, it needs to be pretreated in concentrated nitric acid before being added to other reactants.

[0079] In some embodiments, the sintering temperature is 850°C to 1200°C, and the sintering time is 1 to 8 hours. The sintering temperature is a key parameter affecting the preparation of the zirconium germanate-based orange colorant. If the temperature is too low, the activation energy for sintering cannot be reached, the electronic transition cannot be excited, and thus the orange colorant cannot be formed. If the temperature is too high, on the one hand, energy is wasted, and on the other hand, the material can be vitrified, which affects the subsequent processing and coloring. With a higher temperature, the material can be decomposed into various oxides. Of course, the sintering temperature and the sintering time are interrelated. The higher the sintering temperature, the shorter the sintering time can be to a certain extent. If the sintering temperature is slightly lower, the material migration speed is slow, and the sintering time needs to be delayed to a certain extent to promote sufficient reaction.

[0080] In some embodiments, the zirconium germanate-based orange colorant is applied in the fields of plastics, coatings, enamel, ceramics or glass. It can be understood that when the plastics, coatings, enamel, ceramics or glass need to be orange, the zirconium germanate-based orange colorant can be added to the raw materials for preparing the above-mentioned materials, and then mixed to obtain the orange color. For example, when preparing orange ceramics, the zirconium germanate-based orange colorant, ceramic glaze and water can be mixed to obtain a mixed slurry, and then the mixed slurry is coated on the surface of the ceramic body and sintered to form an orange glaze on the surface of the ceramic. When preparing orange coatings, the zirconium germanate-based orange colorant is only needed to be added to the coating raw materials, and then mixed to obtain the orange coatings.

[0081] In one specific embodiment, Zr 0.9 Tb 0.1 The Zr

[0082] In another embodiment, Zr 0.8 Tb0.2 GeO4 orange pigment was added to epoxy resin coating at a concentration of 3% to prepare an orange paint. This paint, when applied to metal surfaces, exhibits good adhesion and weather resistance, high orange saturation, and excellent decorative effect.

[0083] In yet another embodiment, Zr 0.95 Tb 0.05 GeO4 orange pigment is used in ceramic glazes at a dosage of 5%. When fired at 1200℃, the resulting ceramic products exhibit a stable orange color with uniform luster, good high-temperature stability, and are not prone to volatilization or decomposition.

[0084] In a preferred embodiment, Zr 0.7 Tb 0.3 GeO4 orange pigment is used in enamel processing at a dosage of 4%. After firing at a high temperature of 800-850℃, the enamel layer exhibits a bright orange color with uniform color, strong adhesion, and resistance to acid and alkali corrosion.

[0085] In another preferred embodiment, Zr 0.9 Tb 0.1 GeO4 orange pigment is added to the glass melt at a rate of 2%, and then melted and formed at 1450℃. The resulting colored glass products are transparent orange with uniform and stable color and excellent optical properties.

[0086] The following will provide a detailed description of the zirconium germanate-based orange pigment, its preparation method, and its application, using specific implementation examples.

[0087] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0088] Examples 1-6

[0089] This embodiment provides a sol-gel method for preparing zirconate germanate-based orange pigment:

[0090] Table 1

[0091]

[0092] The specific steps of Examples 1-5 are as follows:

[0093] Zirconium, germanium, and terbium sources were added to 100g of a 1:3 HCl solution in a specific molar ratio and stirred and sonicated until fully dissolved. After complete dissolution, 10g of PO was quickly added to the mixture. As the viscosity gradually increased, the stirring speed was slowed down. Once a uniform gel was formed, the mixture was placed in a water bath and heated at 60°C for 1 hour. After cooling, the gel was crushed and dried in an oven at 150°C for 10 hours. After coarse crushing, drying was continued until a dry gel was obtained. The powder mass was weighed, and 5% LiF (by weight of the powder) was added as a mineralizer. The mixture was ground uniformly and sintered at 850°C for 1 hour. After the furnace temperature dropped to room temperature, the powder was ground, removed, and washed. Deionized water (4-5 times the weight of the powder) was added to the ground powder for washing. The mixture was ultrasonically stirred for 3-5 minutes and centrifuged at 4500rpm for 5 minutes. The supernatant was discarded to obtain the powder. This process was repeated 3 times, and the powder was dried at 80°C to obtain the finished powder.

[0094] The specific steps of Example 6 are as follows:

[0095] Germanium, zirconium, and terbium sources were mixed in a molar ratio of 1:0.9:0.1 and added to 100g of 1:3 HCl. The mixture was stirred and sonicated until fully dissolved. After complete dissolution, 30g of citric acid was quickly added to the mixture. As the viscosity increased, the stirring speed was slowed down until a uniform gel was formed. The mixture was then placed in a water bath and heated at 80°C for 1 hour. After cooling, the gel was crushed and dried in an oven at 150°C for 10 hours. After coarse crushing, further drying was continued until a dry gel was obtained. The powder mass was weighed, and 5% LiF (by weight of the powder) was added as a mineralizer. The mixture was ground uniformly and sintered at 1000°C for 2 hours. After the furnace temperature dropped to room temperature, the powder was ground again, washed, and 4-5 times its weight of deionized water was added to the ground powder for washing. The mixture was ultrasonically stirred for 5 minutes and then centrifuged at 4500rpm for 5 minutes. The supernatant was discarded to obtain the powder. This process was repeated 3 times, followed by drying at 80°C to obtain the final powder.

[0096] Examples 7-11

[0097] This embodiment provides a co-precipitation method for preparing zirconium germanate-based orange pigment:

[0098] Table 2

[0099]

[0100] A second mixture is obtained by adding zirconium, germanium, and terbium sources to acid in a specific molar ratio until they are fully dissolved. Specifically, zirconium chloride is selected as the zirconium source, germanium tetrachloride as the germanium source, and terbium tetraoxide as the terbium source. Appropriate amounts of these raw materials are weighed according to the above molar ratio and added to a beaker containing an appropriate amount of nitric acid. The mixture is stirred at 50°C for 1.5 hours to ensure complete dissolution and the formation of a homogeneous solution.

[0101] Add ammonia to adjust the pH of the second mixture to above 9.5 to obtain an alkaline solution. Specifically, under continuous stirring, slowly add 25% ammonia to the above solution until the pH of the solution stabilizes at around 10, and continue stirring for 30 minutes to ensure that the reaction is complete.

[0102] The alkaline solution was allowed to stand and then centrifuged to obtain the precipitate. Specifically, the alkaline solution was allowed to stand for 2 hours, then centrifuged at 6000 rpm for 15 minutes. The supernatant was discarded, the precipitate was collected, and washed three times with deionized water. After each wash, the precipitate was centrifuged again.

[0103] After drying the precipitate, a certain amount of mineralizer is added and sintered to obtain a sintered body. Specifically, the collected precipitate is dried at 90°C for 24 hours, ground into fine powder, and then thoroughly mixed with 1.5% by weight of lithium fluoride as a mineralizer. The mixture is then placed in an alumina crucible and heated to 900°C in a muffle furnace at a heating rate of 3°C / min. After holding at this temperature for 5 hours, the mixture is cooled to room temperature with the furnace to obtain the sintered body.

[0104] The sintered body was ground, washed, and dried to obtain zirconium germanate-based orange pigment. Specifically, the sintered body was ground into fine powder in an agate mortar, then washed repeatedly with deionized water five times. After each wash, the product was centrifuged, and finally the washed product was dried at 85°C for 10 hours to obtain the final zirconium germanate-based orange pigment.

[0105] Examples 12-16

[0106] This embodiment provides a solid-state method for preparing zirconium germanate-based orange pigment:

[0107] Table 3

[0108]

[0109]

[0110] Weigh out GeO2, ZrO2, and Tb4O7 according to the molar fractions of Ge, Zr, and Tb listed in Table 3, mix thoroughly to obtain a mixture, add 5% LiF by mass of the mixture and grind thoroughly; then place it in a crucible of appropriate size and sinter it in a muffle furnace at 1200℃ for 8 hours. After the furnace temperature drops to room temperature, grind the powder, take it out and wash it, pour the ground powder into a centrifuge tube and weigh out 4 to 5 times the weight of the powder and pour it into the centrifuge tube, perform ultrasonic stirring for 5 minutes, centrifuge at 4500 rpm for 5 minutes, discard the supernatant to obtain the powder, repeat the operation 3 times and then dry at 80℃ to obtain the finished powder.

[0111] The test examples yielded physical images, XRD patterns, diffuse reflectance spectra, and LAB values ​​of the zirconium germanate-based orange pigment. The testing method was as follows:

[0112] XRD pattern: Instrument model used: D8-Advance, Bruker;

[0113] Testing standards: Cu Kα radiation (λ=0.15418nm) was used as the X-ray source, with an operating voltage of 40kV and a current of 40mA. The scanning range was set to 10°–120° (2θ), with a step size of 0.02°; sample morphology (powder).

[0114] Diffuse reflectance spectrum: (UV-3600, Shimadzu, Japan) Total reflectance spectrum was acquired in the wavelength range of 200–2500 nm, with BaSO4 as a white plate reference.

[0115] LAB values: Color parameters are characterized using the CIELAB colorimetric system (colorimeter model YS30,3NH), where L* represents lightness, a* is the red-green value, and b* is the yellow-blue value.

[0116] Figure 1 The image shows a physical sample of the zirconium germanate-based orange pigment prepared by the sol-gel method. Visually, the prepared zirconium germanate-based orange pigment exhibits a uniform orange color with a particle size between 0.5 and 5 μm. When x = 0.05, the pigment is light orange; when x = 0.1 and x = 0.15, the pigment is bright orange; when x = 0.2, the pigment is deep orange; and when x = 0.3, the pigment is dark orange.

[0117] Figure 2 The XRD patterns of the zirconium germanate-based orange pigment prepared by the sol-gel method are shown. The XRD patterns indicate that the XRD diffraction peaks in Examples 1-5 are consistent with those of zirconium germanate, suggesting that doping did not alter the crystal morphology of zirconium germanate or generate any new phases. However, it should be noted that while the XRD diffraction peak in Example 2 is consistent with that of zirconium germanate, the peak intensities in other examples are lower. This indicates that the solid solution ability gradually weakens and the crystallinity gradually decreases with increasing doping concentration.

[0118] Figure 3 The diffuse reflectance spectrum of zirconium germanate-based orange pigments prepared by the sol-gel method (PO) shows that the pigments exhibit strong orange fluorescence emission. They efficiently absorb 15%–25% of blue-violet light below 520 nm, and the orange-red light at 620 nm–720 nm is a high reflectance region with a reflectance of 75%–90%. The main emission peak is located at 580 nm–590 nm, which is mainly attributed to the 5D4→7F5 transition of Tb3+ ions.

[0119] Figure 4 The XRD pattern of the zirconium germanate-based orange pigment prepared by sol-gel method with citric acid is shown. As can be seen from the XRD pattern, the pigment prepared by adding citric acid by sol-gel method with 10 wt% Tb in Example 6 has the same XRD pattern as that of zirconium germanate. This indicates that the preparation method does not change the crystal morphology of zirconium germanate and no new phase is generated.

[0120] Figure 5 The diffuse reflectance spectrum of the zirconium germanate-based orange pigment prepared by sol-gel method with citric acid is shown. From the diffuse reflectance spectrum, it can be seen that in Example 6, the pigment prepared by adding citric acid using the sol-gel method with 10 wt% Tb also exhibits orange fluorescence emission. However, its reflectance in the 600 nm–800 nm wavelength range is only 40%. Compared with Example 2, which uses the same amount of Tb in the sol-gel method (PO), its reflectance in the orange wavelength range is significantly lower. This indicates that the sol-gel method (PO) has a stronger coloring ability than the zirconium germanate-based orange pigment prepared by sol-gel method with citric acid.

[0121] Figure 6 The XRD patterns of the zirconium germanate-based orange pigment prepared by the co-precipitation method are shown. The XRD diffraction peaks in Examples 7-11 are consistent with those of zirconium germanate, indicating that doping did not change the crystal morphology of zirconium germanate or generate any new phases. However, it should be noted that in Examples 8-9, when 10wt% to 15wt% of Tb was added, the XRD diffraction peak intensities were consistent with those of zirconium germanate. In other examples, the diffraction peak intensities were inconsistent with those of zirconium germanate, indicating that the solid solution ability gradually weakens and the crystallinity gradually decreases with increasing doping amount.

[0122] Figure 7 The diffuse reflectance spectra of the zirconium germanate-based orange pigment prepared by the co-precipitation method are shown. From the diffuse reflectance spectra, it can be seen that in Examples 7-11, the 620nm-720nm orange-red light region is a high-reflectance region, with reflectance reaching 75%-90%. The main emission peak is located at 580nm-590nm, which is mainly attributed to Tb. 3+ The 5D4→7F5 transition of the ion exhibits the same absorption and reflection characteristics as in Examples 1-5.

[0123] Figure 8 The diffuse reflectance spectrum of the zirconium germanate-based orange pigment prepared by solid-state method is shown. It can be seen from the diffuse reflectance spectrum that the powders prepared in Examples 12, 13, and 16 are in the high reflectance region under orange-red light, with a maximum reflectance of 90%. They exhibit essentially the same absorption and reflection characteristics as Examples 1-11, but show slightly different performance in the blue-violet light absorption band below 520 nm.

[0124] Table 4. LAB values ​​of zirconium germanate-based orange pigments prepared by different methods

[0125]

[0126] Table 4 shows the LAB values ​​of zirconium germanate-based orange pigments prepared by different methods. Figure 4 The main chromaticity parameters include: lightness value L*, ranging from 0 to 100 corresponding to black to white; redness value a*, representing the red-green hue; and yellowness value b*, representing the yellow-blue hue. A larger positive b* value indicates a higher yellowness, while a smaller negative value indicates a higher blueness. LAB values ​​vary depending on the preparation method and doping level. Generally, with the same method, L* (lightness) decreases with increasing doping level, while a* (red-green axis) and b* (yellow-blue axis) increase. With the same doping level, the changes in L* (lightness), a* (red-green axis), and b* (yellow-blue axis) are minimal, indicating that sol-gel method, co-precipitation method, and solid-state synthesis method can all prepare zirconium germanate-based orange pigments. However, it should be noted that pigments prepared by the sol-gel method (PO) and co-precipitation method are brighter, while those prepared by the sol-gel method (Ce) and solid-state synthesis method have slightly lower color brightness. In practical applications, different preparation methods can be selected according to different requirements for color and brightness.

[0127] In summary, zirconium germanate-based orange pigments can be prepared by sol-gel method, co-precipitation method, and solid-state synthesis when 5wt%–30wt% Tb is incorporated into the zirconium germanate. When the Tb content is 10wt%–15wt%, a bright orange color is observed. This also indicates that pigments prepared by sol-gel method (PO) and co-precipitation method have high purity and uniformity, and good color performance. However, the solid-state synthesis method is simpler. All three methods produce zirconium germanate-based orange pigments with good thermal and chemical stability, maintaining color stability at high temperatures and without significant color change within a pH range of 2–12.

[0128] Furthermore, this zirconium germanate-based orange pigment is non-toxic, harmless, environmentally friendly, and safe. It can replace traditional inorganic pigments containing harmful elements such as lead and cadmium, meeting modern green environmental protection requirements. In various application areas, this pigment exhibits good dispersibility and tinting strength, and the amount added can be adjusted according to different application needs to obtain different shades of orange.

[0129] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A zirconium germanate-based orange pigment, characterized in that: The zirconium germanate-based orange pigment matrix is ​​zirconium germanate, and the doping element includes Tb, with a chemical composition of Zr. 1～x Tb x GeO4, where x = 0.05 to 0.

3.

2. The zirconium germanate-based orange pigment Zr according to claim 1 1～x Tb x In GeO4, x = 0.1 to 0.

15.

3. A method for preparing a zirconium germanate-based orange pigment according to claim 1 or 2, characterized in that, The preparation method is one of the following: sol-gel method, co-precipitation method, and solid-phase synthesis method.

4. The method for preparing zirconium germanate-based orange pigment according to claim 3, characterized in that, The sol-gel method includes the following steps: Zirconium source, germanium source and terbium source are added to acid in a certain proportion and allowed to dissolve completely to obtain the first mixture; Add propylene oxide (PO) or citric acid to the first mixture and stir until a sol is formed; The moisture in the sol is evaporated, dried, and then ground into powder. The powder is mixed with a certain amount of mineralizer and then sintered to obtain a sintered body. The sintered body is ground, washed, and dried to obtain the zirconium germanate-based orange pigment.

5. The method for preparing zirconium germanate-based orange pigment according to claim 3, characterized in that, The coprecipitation method includes the following steps: A second mixture is obtained by adding zirconium source, germanium source and terbium source in a certain proportion to acid and dissolving them completely. Ammonia was added to adjust the pH of the second mixture to above 9.5 to obtain an alkaline solution; The alkaline solution was allowed to stand and then centrifuged to obtain a precipitate. The precipitate was dried and then a certain amount of mineralizer was added and sintered to obtain a sintered body. The sintered body is ground, washed, and dried to obtain the zirconium germanate-based orange pigment.

6. The method for preparing zirconium germanate-based orange pigment according to claim 4 or 5, wherein the zirconium source comprises one of zirconium oxychloride octahydrate, zirconium chloride, zirconium propoxide, zirconium oxide, and zirconium sulfate tetrahydrate; the germanium source comprises one of germanium oxide, germanate, germanium tetrachloride, and germanium powder; and the terbium source comprises one of terbium chloride hexahydrate, terbium tetraoxide heptahydrate, and terbium nitrate hexahydrate.

7. The method for preparing zirconium germanate-based orange pigment according to claim 4 or 5, characterized in that, The mineralizing agent is LiF.

8. The method for preparing zirconium germanate-based orange pigment according to claim 4 or 5, characterized in that, The sintering temperature is 850℃~1200℃, and the sintering time is 1~8 hours.

9. The method for preparing a zirconium germanate-based orange pigment according to claim 3, characterized in that, The solid-phase synthesis method includes the following steps: Zirconia, germanium oxide, terbium oxide and mineralizing agent are mixed in a certain proportion to obtain a third mixture; The third mixture is sintered for a period of time to obtain a third sintered body; The third sintered body was ground, washed, and dried to obtain zirconium germanate-based orange pigment.

10. The use of a zirconium germanate-based orange pigment as described in any one of claims 1-2, characterized in that: As an orange pigment, it is used in the fields of plastics, coatings, enamel, ceramics, or glass.

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