A method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method

Abstract

The invention provides a method for preparing ultrafine praseodymium-zirconium yellow ceramic pigment by a molten salt-assisted hydrothermal method. The method uses a zirconium source, a silicon source and a praseodymium source as raw materials, prepares a Pr-ZrSiO4 precursor by a hydrothermal method, and then obtains the praseodymium-zirconium yellow ceramic pigment with excellent coloring performance by low-temperature heat treatment assisted by molten salt. The crystal dissolution-precipitation-growth process of the Pr-ZrSiO4 pigment is regulated by the molten salt, and a steric hindrance effect is generated during the low-temperature heat treatment process, thereby realizing low-temperature synthesis of fine, highly dispersible Pr-ZrSiO4 pigment with excellent coloring performance, without the need for subsequent ball milling treatment, with uniform particle size distribution and good dispersibility, and with a particle size of less than 100 nm, so that the pigment is suitable for use in fields with high requirements on particle size such as ceramic inkjet printing for preparing ceramic ink. The invention also has simple process, short preparation cycle, low energy consumption, and is easy to mass produce, and is of great significance for promoting the technological progress and application development of the Pr-ZrSiO4 yellow pigment.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic non-metallic materials and relates to a method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by a molten salt-assisted hydrothermal method. Background Art

[0002] Zirconium silicate ZrSiO4 is an island silicate with high melting point, excellent chemical stability and resistance to glaze melt corrosion. It is widely used in refractory materials, thermal barrier coatings and high-temperature ceramic pigments. Among them, zirconium silicate-based ceramic pigments are currently the only pigments of the same type that can produce three colors of red, yellow and blue, such as iron zirconium red Fe-ZrSiO4, praseodymium zirconium yellow Pr-ZrSiO4 and vanadium zirconium blue V-ZrSiO4. They have good miscibility and occupy an important position in the field of high-temperature ceramic decoration. Among them, praseodymium zirconium yellow has attracted much attention for its bright yellow tone.

[0003] At present, ceramic inkjet printing decoration technology has been widely used in the field of architectural ceramic decoration. By making ceramic pigments into ceramic inks, the ceramic inks are directly printed onto the ceramic surface using a computer-controlled printer. Ceramic inks are based on ultrafine ceramic pigments, and the particle size of the pigment particles is required to be less than 1 μm. Existing methods for preparing praseodymium zirconium yellow ceramic pigments can be mainly divided into two categories: one is the solid phase method and the other is the liquid phase method. The traditional solid phase method uses oxides as precursors, which have low activity. The prepared pigment particles have large particle sizes and uneven sizes (about 3 to 20 μm), which is difficult to meet the application requirements in glazes and requires further ball milling. However, subsequent ball milling will lead to a significant reduction in the color performance of the pigment. In order to solve the above problems, scientific researchers have shifted from the traditional solid phase method to the liquid phase method with better uniformity and reaction activity, including sol-gel method, non-hydrolytic sol-gel method, hydrothermal method, co-precipitation method, microwave-assisted synthesis method, etc. Gao Yanfeng et al. prepared nano-praseodymium zirconium yellow ceramic pigment by a hydrothermal method, in which praseodymium nitrate, a soluble silicon source aqueous solution and a soluble zirconium source aqueous solution were uniformly mixed to obtain a mixed solution; the pH value of the solution was adjusted, and after a hydrothermal reaction at 180-240°C for 10-20 hours, the obtained precursor was calcined at 800-1200°C for 1-4 hours and then ground to obtain a nano-praseodymium zirconium yellow ceramic pigment with a particle size of less than 500nm and a yellowness value b*=39.57-60.04. Chen et al. synthesized praseodymium zirconium yellow ceramic pigment by non-hydrolytic sol-gel method. The method used anhydrous zirconium tetrachloride, tetraethyl orthosilicate, praseodymium chloride as raw materials, lithium fluoride as mineralizer, refluxed at 110℃ for 12h, and then heat treated at 750℃ for 2h to obtain ultrafine praseodymium zirconium yellow pigment with a particle size of about 0.1-1.3μm and a yellowness value of b*=69.48. However, the pigment powder prepared by liquid phase method is mostly agglomerates in microscopic morphology, with small grain size but adhesion between grains, poor dispersibility, and requires subsequent ball milling process. At present, commercial praseodymium zirconium yellow ceramic ink mainly meets the size requirements of inkjet printing applications by sacrificing the color of pigments. Therefore, the development of an ultrafine Pr-ZrSiO4 yellow ceramic pigment with excellent color rendering performance and dispersibility has become the primary problem to be solved in this field. Summary of the invention

[0004] In view of this, in order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method, the method uses zirconium source, silicon source and praseodymium source as raw materials, prepares Pr-ZrSiO4 precursor by hydrothermal method, and then obtains praseodymium zirconium yellow ceramic pigment with excellent color performance by molten salt assisted low temperature heat treatment, and regulates the crystal dissolution-precipitation-growth process of Pr-ZrSiO4 pigment by molten salt assistance, and produces steric hindrance effect during low temperature heat treatment, thereby realizing low temperature synthesis of fine, highly dispersible and excellent color performance Pr-ZrSiO4 pigment, without subsequent ball milling treatment, uniform particle size distribution and good dispersibility, particle size less than 100nm, suitable for application in ceramic inkjet printing to prepare ceramic ink and other fields with high requirements on particle size; and the present invention has simple process, short preparation cycle, low energy consumption, easy large-scale production, and is of great significance for promoting the technological progress and application development of Pr-ZrSiO4 yellow pigment.

[0005] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0006] A method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method comprises the following steps:

[0007] Step S1: dissolving a zirconium source and a praseodymium source in deionized water successively, and stirring at room temperature until they are completely dissolved to obtain a zirconium precursor solution;

[0008] Step S2: adding a mineralizer to the precursor solution obtained in the above step S1, stirring until fully dissolved to form a gel; then, adding a silicon source, stirring evenly, adjusting the pH value of the mixed solution to obtain a Pr-ZrSiO4 precursor solution, placing the solution in a hydrothermal reactor, and drying after hydrothermal reaction to obtain a Pr-ZrSiO4 precursor powder;

[0009] Step S3: The Pr-ZrSiO4 precursor powder obtained in step S2 is mixed with molten salt and ground, and after heat treatment, the mixture is washed with deionized water for n times to obtain an ultrafine praseodymium zirconium yellow ceramic pigment.

[0010] Furthermore, the zirconium source in step S1 is zirconium oxychloride octahydrate ZrOCl2·8H2O, zirconium tetrachloride ZrCl4, zirconium sulfate tetrahydrate Zr(SO4)2·4H2O, zirconium isopropoxide C 12 H 28 One or more of O4Zr and zirconium acetate Zr(CH3COO)4.

[0011] Furthermore, in step S1, the praseodymium source is one or more of praseodymium chloride PrCl3, praseodymium fluoride PrF3, praseodymium chloride heptahydrate PrCl3·7H2O, and praseodymium nitrate PrN3O9·6H2O.

[0012] Furthermore, in step S2, the silicon source is one or more of tetraethyl orthosilicate TEOS, sodium silicate nonahydrate Na2SiO3·9H2O, and silicon tetrachloride SiCl4; and the mineralizer in step S2 is one or more of lithium fluoride (LiF) and sodium fluoride (NaF).

[0013] Furthermore, the molten salt in step S3 is a composite molten salt formed by one or a combination of alkali metal tungstate, alkali metal molybdate, and alkali metal chloride; the mass ratio of the molten salt to the Pr-ZrSiO4 precursor powder is 0.2 to 5:1.

[0014] Furthermore, the concentration of the zirconium precursor solution is 0.2-0.6 mol / L, wherein the molar ratio of mineralizer: praseodymium source: silicon source: zirconium source is 0.3:0.01-0.15:1.0-1.4:1.0.

[0015] Furthermore, the pH value of the mixed solution is controlled to be 8-10, and n≥3.

[0016] Furthermore, the hydrothermal reaction temperature is 160-180° C. for 12-24 hours; the heat treatment temperature is 700-900° C. for 2-8 hours.

[0017] Furthermore, the ultrafine praseodymium zirconium yellow ceramic pigment obtained in step 3 has a particle size of less than 100 nm and good dispersibility, with chromaticity values ​​of L*=78.02-83.23, a*=-6.72-0.74, and b*=52.31-60.99.

[0018] A molten salt-assisted hydrothermal method is used to prepare ultrafine praseodymium zirconium yellow ceramic pigment, which is prepared by the above-mentioned preparation method.

[0019] Beneficial effects:

[0020] The beneficial effects of the present invention are embodied in:

[0021] (1) The present invention adopts a molten salt-assisted hydrothermal method. First, a small and highly active Pr-ZrSiO4 precursor is pre-synthesized by a hydrothermal method. Then, the molten salt is melted at a low temperature to transform the original three-dimensional solid-phase mass transfer into a two-dimensional liquid-phase mass transfer, which is beneficial to reducing the activation energy of the reaction. More importantly, during the heat treatment process, the molten salt can regulate the dissolution-precipitation-growth process of the Pr-ZrSiO4 crystals. At the same time, combined with its steric hindrance effect, it is beneficial to synthesize a small, highly dispersed Pr-ZrSiO4 yellow ceramic pigment with excellent color performance at a low temperature. No subsequent ball milling treatment is required, and it is expected to be applied to the field of ceramic inkjet printing.

[0022] (2) Compared with the traditional solid phase method and the liquid phase method reported in the literature, the Pr-ZrSiO4 yellow ceramic pigment prepared in the present invention has the characteristics of ultrafine particle size, better dispersibility and color rendering properties, and lower synthesis temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 is the XRD spectrum of the praseodymium zirconium yellow ceramic pigment prepared in Example 1 of the present invention;

[0025] Figure 2 This is a TEM photograph of the praseodymium zirconium yellow ceramic pigment prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Embodiment 1:

[0028] This embodiment provides a method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method, and the steps are as follows:

[0029] (1) ZrOCl2·8H2O and PrCl3·7H2O were used as zirconium source and praseodymium source, respectively, and were added into 60 mL of deionized water at a molar ratio of n(Pr) / n(Zr) of 0.08. The mixture was stirred at room temperature until completely dissolved to obtain a zirconium precursor solution with a concentration of 0.2 mol / L.

[0030] (2) Add the mineralizer LiF to the above precursor solution and stir until it is fully dissolved to form a gel. Then, add the silicon source, stir evenly, and adjust the pH value of the mixed solution to 9 to obtain a Pr-ZrSiO4 precursor solution, wherein the molar ratio of mineralizer: Pr: Si: Zr is 0.3: 0.08: 1.2: 1.0. Place it in a hydrothermal reactor, heat it at 160°C for 12 hours, and then dry it to obtain a Pr-ZrSiO4 precursor powder.

[0031] (3) The Pr-ZrSiO4 precursor powder and NaCl molten salt were mixed and ground in a mass ratio of 1:1, heat treated at 700°C for 6 hours, and then washed with deionized water three times to obtain an ultrafine praseodymium zirconium yellow ceramic pigment.

[0032] This comparative example 1 is based on Example 1 for comparison:

[0033] Comparative Example 1:

[0034] (1) ZrOCl2·8H2O and PrCl3·7H2O were used as zirconium source and praseodymium source, respectively, and were added into 60 mL of deionized water at a molar ratio of n(Pr) / n(Zr) of 0.08. The mixture was stirred at room temperature until completely dissolved to obtain a zirconium precursor solution with a concentration of 0.2 mol / L.

[0035] (2) Add the mineralizer LiF to the above precursor solution and stir until it is fully dissolved to form a gel. Then, add the silicon source, stir evenly, and adjust the pH value of the mixed solution to 9 to obtain a Pr-ZrSiO4 precursor solution, wherein the molar ratio of mineralizer: Pr: Si: Zr is 0.3: 0.08: 1.2: 1.0. Place it in a hydrothermal reactor, heat it at 160°C for 12 hours, and then dry it to obtain a Pr-ZrSiO4 precursor powder.

[0036] (3) The Pr-ZrSiO4 precursor powder is directly heat-treated at 700°C for 6 hours, and then washed with deionized water three times to obtain a praseodymium zirconium yellow ceramic pigment.

[0037] The color rendering performance of the synthetic pigment in Comparative Example 1 is close to that of Example 1, but the particle size of the praseodymium zirconium yellow ceramic pigment is larger, about 15 μm.

[0038] Embodiment 2:

[0039] This embodiment provides a method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method, and the steps are as follows:

[0040] (1) ZrOCl2·8H2O and PrN3O9·6H2O were used as zirconium source and praseodymium source, respectively, and were added into 60 mL of deionized water at a molar ratio of n(Pr) / n(Zr) of 0.10. The mixture was stirred at room temperature until completely dissolved to obtain a zirconium precursor solution with a concentration of 0.4 mol / L.

[0041] (2) Add the mineralizer NaF to the above precursor solution and stir until it is fully dissolved to form a gel. Then, add the silicon source, stir evenly, and adjust the pH value of the mixed solution to 8 to obtain a Pr-ZrSiO4 precursor solution, wherein the molar ratio of mineralizer: Pr: Si: Zr is 0.3: 0.10: 1.0: 1.0. Place it in a hydrothermal reactor, heat it at 180°C for 12 hours, and then dry it to obtain a Pr-ZrSiO4 precursor powder.

[0042] (3) The Pr-ZrSiO4 precursor powder and KCl molten salt are mixed and ground in a mass ratio of 2:1, heat treated at 800°C for 2 hours, and then washed with deionized water three times to obtain an ultrafine praseodymium zirconium yellow ceramic pigment.

[0043] Embodiment 3:

[0044] This embodiment provides a method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method, and the steps are as follows:

[0045] (1) ZrOCl2·8H2O and PrCl3·7H2O were used as zirconium source and praseodymium source, respectively, and were added into 60 mL of deionized water at a molar ratio of n(Pr) / n(Zr) of 0.10. The mixture was stirred at room temperature until completely dissolved to obtain a zirconium precursor solution with a concentration of 0.4 mol / L.

[0046] (2) Add the mineralizer LiF to the above precursor solution and stir until it is fully dissolved to form a gel. Then, add the silicon source, stir evenly, and adjust the pH value of the mixed solution to 10 to obtain a Pr-ZrSiO4 precursor solution, wherein the molar ratio of mineralizer: Pr: Si: Zr is 0.3: 0.10: 1.1: 1.0. Place it in a hydrothermal reactor, heat it at 180°C for 12 hours, and then dry it to obtain a Pr-ZrSiO4 precursor powder.

[0047] (3) The Pr-ZrSiO4 precursor powder, KCl and LiCl composite molten salt are mixed and ground in a mass ratio of 1:0.5:0.5, heat treated at 900°C for 2 hours, and then washed with deionized water three times to obtain an ultrafine praseodymium zirconium yellow ceramic pigment.

[0048] Embodiment 4:

[0049] This embodiment provides a method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method, and the steps are as follows:

[0050] (1) ZrCl4 and PrCl3·7H2O were used as zirconium source and praseodymium source, respectively, and were added into 60 mL of deionized water at a molar ratio of n(Pr) / n(Zr) of 0.06. The mixture was stirred at room temperature until completely dissolved to obtain a zirconium precursor solution with a concentration of 0.6 mol / L.

[0051] (2) Add the mineralizer LiF to the above precursor solution and stir until it is fully dissolved to form a gel. Then, add the silicon source, stir evenly, and adjust the pH value of the mixed solution to 10 to obtain a Pr-ZrSiO4 precursor solution, wherein the molar ratio of mineralizer: Pr: Si: Zr is 0.3: 0.06: 1.4: 1.0. Place it in a hydrothermal reactor, heat it at 170°C for 24 hours, and then dry it to obtain a Pr-ZrSiO4 precursor powder.

[0052] (3) The Pr-ZrSiO4 precursor powder, KCl and LiCl composite molten salt are mixed and ground in a mass ratio of 1:0.4:0.6, heat treated at 800°C for 4 hours, and then washed with deionized water three times to obtain an ultrafine praseodymium zirconium yellow ceramic pigment.

[0053] Embodiment 5:

[0054] This embodiment provides a method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method, and the steps are as follows:

[0055] (1) ZrOCl2·8H2O and PrCl3·7H2O were used as zirconium source and praseodymium source, respectively, and were added into 60 mL of deionized water at a molar ratio of n(Pr) / n(Zr) of 0.01. The mixture was stirred at room temperature until completely dissolved to obtain a zirconium precursor solution with a concentration of 0.2 mol / L.

[0056] (2) Add the mineralizer LiF to the above precursor solution and stir until it is fully dissolved to form a gel. Then, add the silicon source, stir evenly, and adjust the pH value of the mixed solution to 9 to obtain a Pr-ZrSiO4 precursor solution, wherein the molar ratio of mineralizer: Pr: Si: Zr is 0.3: 0.08: 1.2: 1.0. Place it in a hydrothermal reactor, heat it at 160°C for 12 hours, and then dry it to obtain a Pr-ZrSiO4 precursor powder.

[0057] (3) The Pr-ZrSiO4 precursor powder and NaCl molten salt were mixed and ground in a mass ratio of 1:0.2, and after heat treatment at 700°C for 6 hours, the mixture was washed with deionized water three times to obtain an ultrafine praseodymium zirconium yellow ceramic pigment.

[0058] Embodiment 6:

[0059] This embodiment provides a method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method, and the steps are as follows:

[0060] (1) ZrCl4 and PrCl3·7H2O were used as zirconium source and praseodymium source, respectively, and were added into 60 mL of deionized water at a molar ratio of n(Pr) / n(Zr) of 0.15. The mixture was stirred at room temperature until completely dissolved to obtain a zirconium precursor solution with a concentration of 0.6 mol / L.

[0061] (2) Add the mineralizer LiF to the above precursor solution and stir until it is fully dissolved to form a gel. Then, add the silicon source, stir evenly, and adjust the pH value of the mixed solution to 10 to obtain a Pr-ZrSiO4 precursor solution, wherein the molar ratio of mineralizer: Pr: Si: Zr is 0.3: 0.06: 1.4: 1.0. Place it in a hydrothermal reactor, heat it at 170°C for 24 hours, and then dry it to obtain a Pr-ZrSiO4 precursor powder.

[0062] (3) The Pr-ZrSiO4 precursor powder, KCl and LiCl composite molten salt are mixed and ground in a mass ratio of 1:2:3, heat treated at 800°C for 4 hours, and then washed with deionized water three times to obtain an ultrafine praseodymium zirconium yellow ceramic pigment.

[0063] The high color rendering ultrafine Pr-ZrSiO4 yellow ceramic pigment prepared in Example 1 of the present invention is as follows Figure 1 As shown in Figure 2, the characteristic diffraction peaks of zirconium silicate (JCPDS 06-0266) appeared; Figure 2 As shown, the synthesized Pr-ZrSiO4 yellow ceramic pigment has uniform particle size and a particle size of less than 100 nm, has good dispersibility, and meets the application standards in the inkjet printing field.

[0064] The color performance test is as follows:

[0065] The zirconium silicate-based ceramic pigment prepared in the embodiment of the present invention was characterized by using a fully automatic whiteness meter. First, a black tube and a standard white plate were used for calibration, and then the pigment powder was placed in a mold and pressed into a sheet (30*2 mm). The chromaticity value was calculated by the whiteness meter. The results are shown in Table 1, showing excellent color rendering performance.

[0066] Table 1 Chromaticity values ​​of Pr-ZrSiO4 yellow ceramic pigments prepared in the present invention

[0067]

[0068] In summary, the present invention provides a method for preparing a highly color-rendering ultrafine zirconium silicate-based nano ceramic pigment, which utilizes silicon-containing nano minerals or silica ash as a silicon source, removes impurities through simple acid washing, and provides a highly reactive silicon source with nanostructure or nanopores, which is beneficial to reducing the activation energy of the solid phase reaction, synthesizing a zirconium silicate-based ceramic pigment with both high color development and ultrafine powder size at low temperature, mixing and grinding the silicon source, zirconium source, colorant and mineralizer according to the mass ratio at room temperature, and obtaining an ultrafine zirconium silicate-based ceramic pigment with excellent color performance, uniform particle size distribution and good dispersibility through low temperature heat treatment, which is suitable for fields with high requirements on particle size such as ceramic inkjet printing. The raw materials used in the present invention are low in price, the process flow is simple, no subsequent water washing and acid washing are required, the reaction temperature is low, the obtained zirconium silicate-based pigment powder has uniform size and a particle size of less than 1 μm, is suitable for large-scale production, and has a strong prospect for promotion and application.

[0069] The above description is not intended to impose any form of limitation on the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt assisted hydrothermal method, characterized in that: The preparation method comprises the following steps: Step S1: dissolving a zirconium source and a praseodymium source in deionized water successively, and stirring at room temperature until they are completely dissolved to obtain a zirconium precursor solution; Step S2: adding a mineralizer to the precursor solution obtained in the above step S1, stirring until fully dissolved to form a gel; then, adding a silicon source, stirring evenly, adjusting the pH value of the mixed solution to obtain a Pr-ZrSiO4 precursor solution, placing the solution in a hydrothermal reactor, and drying after hydrothermal reaction to obtain a Pr-ZrSiO4 precursor powder; Step S3: the Pr-ZrSiO4 precursor powder obtained in step S2 is mixed with molten salt and ground, and after heat treatment, the mixture is washed with deionized water for n times to obtain an ultrafine praseodymium zirconium yellow ceramic pigment; The zirconium source in step S1 is zirconium oxychloride octahydrate ZrOCl2·8H2O, zirconium tetrachloride ZrCl4, zirconium sulfate tetrahydrate Zr(SO4)2·4H2O, zirconium isopropoxide C 12 H 28 One or more of O4Zr and zirconium acetate Zr(CH3COO)4; The praseodymium source in step S1 is one or more of praseodymium chloride PrCl3, praseodymium fluoride PrF3, praseodymium chloride heptahydrate PrCl3·7H2O, and praseodymium nitrate PrN3O9·6H2O; In step S2, the silicon source is one or more of tetraethyl orthosilicate TEOS, sodium silicate nonahydrate Na2SiO3·9H2O, and silicon tetrachloride SiCl4; in step S2, the mineralizer is one or more of lithium fluoride LiF and sodium fluoride NaF; The molten salt in step S3 is a composite molten salt formed by one of alkali metal tungstate, alkali metal molybdate, and alkali metal chloride or a combination thereof; the mass ratio of the molten salt to the Pr-ZrSiO4 precursor powder is 0.2 to 5:1; The ultrafine praseodymium zirconium yellow ceramic pigment obtained in step S3 has a particle size of less than 100 nm and good dispersibility, and a chromaticity value of L*=78.02-83.23, a*=-6.72-0.74, and b*=52.31-60.99; The concentration of the zirconium precursor solution is 0.2-0.6 mol / L, wherein the molar ratio of mineralizer: praseodymium source: silicon source: zirconium source is 0.3:0.01-0.15:1.0-1.4:1.

0.

2. A method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt-assisted hydrothermal method as claimed in claim 1, characterized in that: The pH value of the mixed solution is controlled to be 8-10, and n≥3.

3. A method for preparing ultrafine praseodymium zirconium yellow ceramic pigment by molten salt-assisted hydrothermal method as claimed in claim 1, characterized in that: The hydrothermal reaction temperature is 160-180° C. for 12-24 hours; the heat treatment temperature is 700-900° C. for 2-8 hours.

4. A molten salt-assisted hydrothermal method for preparing ultrafine praseodymium zirconium yellow ceramic pigment, characterized in that: The pigment is prepared by any one of the preparation methods of claims 1-3.

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