Praseodymium colorant, method for preparing praseodymium colorant, and method for preparing green decorative ceramic plate using pure ammonia atmosphere

Abstract

The present invention belongs to the field of architectural ceramics and relates to a praseodymium-based pigment, a method for preparing the pigment, and a method for preparing green decorative ceramic panels using a pure ammonia atmosphere. The praseodymium-based pigment has a core-shell structure composed of a zirconium silicate core and a borosilicate glass shell uniformly distributed with +3-valent Pr ions. Because the zirconium silicate matrix has excellent high-temperature stability, the resulting core-shell green pigment also exhibits excellent high-temperature stability. During high-temperature use, it is not easily eroded by other glazes, resulting in a decorative ceramic product with a good three-dimensional appearance and a smooth surface free of noticeable pores.

Description

Technical Field

[0001] The invention belongs to the field of building ceramics and relates to a praseodymium colorant, a method for preparing the praseodymium colorant, and a method for preparing a green decorative ceramic plate using a pure ammonia atmosphere. Background Art

[0002] The Color Pigments Manufacturers Association (CPMA) displayed a variety of common green pigments, including Cr2O3 (3-05-3), Ca3Cr2Si3O 12 (4-07-3), Ni2SiO4(5-45-3), Co(AlCr)2O4(13-29-2), CoCr2O4(13-30-3), Co2TiO4(13-31-3), etc. These pigments use heavy metals such as Ni, Co, and Cr as coloring units. However, heavy metal ions (especially hexavalent chromium ions) are highly toxic and pose a potential threat to the environment and human health.

[0003] Rare earth oxides have a rich 4f electron layer structure. Within the visible light range, the energy level transitions of 4f electrons can absorb specific wavelengths of light, thereby producing color. They are non-toxic and environmentally friendly coloring oxides. Praseodymium oxide is a common coloring oxide. Currently, the architectural ceramics industry uses zirconium silicate as a matrix, doping it with praseodymium oxide to produce vibrant zirconium-praseodymium yellow pigments. However, there are currently no reports of green praseodymium-based ceramic pigments. Summary of the Invention

[0004] To address the above issues, the present invention provides a core-shell praseodymium-based pigment, a method for preparing the pigment, and a method for preparing green decorative ceramic panels using a pure ammonia atmosphere. Because the zirconium silicate matrix possesses excellent high-temperature stability, the resulting core-shell green pigment also exhibits excellent high-temperature stability. During high-temperature use, it is not easily eroded by other glazes, resulting in decorative ceramic products with a strong three-dimensional effect and a smooth surface free of noticeable pores.

[0005] In a first aspect, the present invention provides a praseodymium-based colorant having a core-shell structure comprising zirconium silicate as a core and borosilicate glass with +3-valent Pr ions uniformly distributed therein as a shell.

[0006] In a second aspect, the present invention provides a method for preparing a praseodymium-based colorant. The method for preparing the praseodymium-based colorant comprises: x Zr 1-xPraseodymium oxide, silicon dioxide, and zirconium oxide are weighed in a stoichiometric ratio of SiO4 (0<x ≤ 0.08), and then a boron frit is added. After being fully mixed, the mixture is dried to form a powder. The powder is then sintered and crushed to obtain the praseodymium-based colorant.

[0007] Preferably, the chemical composition of the boron frit includes, by mass percentage, Al2O3: 7.8%~12%, SiO2: 30%~41%, Fe2O3: 0.05%~0.2%, CaO: 0.15%~0.5%, K2O: 5.5%~6.5%, Na2O: 14%~17%, B2O3: 28%~32%, and BaO: 0.15%~0.35%.

[0008] Preferably, the amount of the boron frit is 3% to 8% of the total mass of praseodymia, silicon dioxide and zirconium oxide.

[0009] Preferably, the sintering comprises: keeping the temperature at 900-1000° C. for 1-2 hours, and then keeping the temperature at 1250-1350° C. for 1.5-2.5 hours.

[0010] In a third aspect, the present invention provides a method for producing a green decorative ceramic plate using a pure ammonia atmosphere. The method comprises the following steps: inkjet printing a pattern of ordinary ink on the surface of a green brick; positioning a pattern of glue on the surface of the green brick after the ordinary ink pattern is printed; applying a praseodymium-based colorant to the surface of the green brick after the glue pattern is printed; applying a dry granular glaze to the surface of the green brick after the praseodymium-based colorant is applied; and firing and polishing the green brick after the dry granular glaze is applied in a pure ammonia atmosphere to produce the green decorative ceramic plate.

[0011] Preferably, the particle size of the praseodymium-based colorant is 20-40 mesh.

[0012] Preferably, the chemical composition of the dry granular glaze includes, by mass percentage, SiO2: 50%~61%, Al2O3: 9.5%~15%, Fe2O3: 0.05%~0.2%, CaO: 6.5%~12%, MgO: 0.85%~1.2%, K2O: 4.5%~6.3%, Na2O: 1.8%~2.2%, P2O5: 0.15%~0.3%, and ZnO: 5.5%~9.5%.

[0013] Preferably, the dry granular glaze is applied by pouring glaze; preferably, the specific gravity of the dry granular glaze is 1.45~1.55g / cm 3 , glaze application amount is 960 ~1100g / m 2 .

[0014] Preferably, the grayscale of the glue pattern is 30% to 40%.

[0015] Preferably, the firing temperature is 1130-1180° C., and the firing period is 40-45 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 These are actual pictures of the praseodymium-based colorants of Examples 1-2 and Comparative Examples 1-2.

[0017] Figure 2 This is a SEM image of the praseodymium-based colorant of Example 2.

[0018] Figure 3 This is the XRD pattern of the praseodymium-based color material of Example 2.

[0019] Figure 4 It is a brick surface effect diagram of the green decorative ceramic plate of Example 5.

[0020] Figure 5 This is a brick surface effect diagram of the decorative ceramic plate of Comparative Example 3. DETAILED DESCRIPTION

[0021] The present invention is further illustrated by the following embodiments. It should be understood that the following embodiments are intended to illustrate the present invention only and are not intended to limit the present invention. The following exemplary embodiments describe the praseodymium-based colorant, a method for preparing the praseodymium-based colorant, and a method for preparing a green decorative ceramic plate using a pure ammonia atmosphere.

[0022] As previously described, the present invention provides a novel praseodymium-based pigment. This praseodymium-based pigment has a core-shell structure consisting of a zirconium silicate core and a borosilicate glass shell containing uniformly distributed Pr ions (+3). The borosilicate glass encapsulates the surface of the zirconium silicate. The Pr ions (+3) within this core-shell structure act as coloring centers, producing a green color.

[0023] According to Pr x Zr 1-x Weigh praseodymia, silica, and zirconia in a stoichiometric ratio of SiO4 (0 < x ≤ 0.08). Thoroughly grind and disperse the praseodymia, silica, zirconia, and an appropriate amount of boron frit, then dry to form a powder. The amount of boron frit used can be 3% to 8% of the total mass of praseodymia, silica, and zirconia. If the amount of boron frit is too low, the borosilicate glass will not fully encapsulate the zirconium silicate matrix, resulting in a yellow colorant. If the amount of boron frit is too high, the glass network structure will become unstable, forming a heterogeneous phase and causing uneven coloration. This will also exacerbate the agglomeration of the colorant particles, hindering dispersion.

[0024] In some embodiments, the chemical composition of the boron frit includes, by mass percentage, Al2O3: 7.8%-12%, SiO2: 30%-41%, Fe2O3: 0.05%-0.2%, CaO: 0.15%-0.5%, K2O: 5.5%-6.5%, Na2O: 14%-17%, B2O3: 28%-32%, and BaO: 0.15%-0.35%. Controlling the chemical composition of the boron frit within the above range can accelerate the nucleation of zirconium silicate. Furthermore, this allows for the rational control of the high-temperature viscosity of the boron frit, reducing the occurrence of defects such as blisters, pinholes, and glaze concavity during the process of applying praseodymium-based pigment dry particles to the glue dry particles and then covering them with dry granule glaze.

[0025] The powder is placed in a sagger and sintered at an appropriate temperature. The sintering schedule includes: holding at 900-1000°C for 1-2 hours, then holding at 1250-1350°C for 1.5-2.5 hours. For example, the sintering schedule is: first raise the temperature to 1000°C, hold for 1 hour, then raise the temperature to 1250-1350°C and hold for 1.5 hours.

[0026] During the synthesis of the praseodymium-based pigment, the presence of boron frit helps to reduce the synthesis temperature of the solid-phase reaction. When the sintering temperature is raised to about 900-1000°C, silicon dioxide and zirconium oxide react at high temperature to form zirconium silicate, while the boron frit is wrapped around the surface of the zirconium silicate particles in the form of borosilicate glass to form inclusions. At this time, the praseodymium ions in the zirconium silicate lattice mainly present a +4 valence, and the overall color tone is yellowish. Continuing to increase the sintering temperature to 1250-1350°C, the praseodymium ions undergo a high-temperature transformation, Pr 4+ Converted to Pr 3+ , and migrates into the shell of borosilicate glass and is retained, forming a green colored center.

[0027] The sintered praseodymium pigment is crushed into a certain particle size.

[0028] The following is an exemplary description of a method for preparing a green decorative ceramic plate using a pure ammonia atmosphere.

[0029] The brick powder is pressed and formed into a brick. A brick powder commonly used in the art can be used. For example, but not limited to, the chemical composition of the brick powder includes, by mass percentage, SiO2: 60-70%, Al2O3: 19-25%, Fe2O3: 0.5-1.5%, TiO2: 0.2-0.5%, CaO: 0.2-0.8%, MgO: 0.3-0.8%, K2O: 2.0-4.0%, Na2O: 1.5-3.5%, and loss on ignition: 4.0-6.0%.

[0030] The molding method includes but is not limited to dry pressing.

[0031] The bricks are dried. The moisture content of the dried bricks can be controlled within 0.2-0.5 wt%. The drying temperature can be 110-130°C. The drying time can be 0.5-1.5 hours.

[0032] Printing a pattern with ordinary ink on the surface of the brick. The texture and color of the inkjet-printed pattern can be adapted to the needs. The ink pattern can be formed by inkjet printing ordinary ink using an inkjet printer.

[0033] After the ordinary ink pattern is inkjet printed, an inkjet-printed glue pattern is positioned on the surface of the brick. That is, an inkjet printer is used to print an appropriate amount of grayscale glue at the location where the colorant needs to be bonded. The glue pattern can be printed using an inkjet printer. The glue pattern can be printed using a dual-channel inkjet printer. The grayscale of the glue pattern of each channel can be independently 30% to 40%. By controlling the grayscale of the glue pattern within the above range, the amount of glue used can be controlled. Preferably, the amount of glue applied is less than 20g / m 2 .

[0034] The praseodymium colorant is applied to the surface of the brick after the glue pattern has been inkjet-printed. By evenly spreading the new praseodymium colorant, crushed to a certain particle size, on the brick surface, the praseodymium colorant adheres to the surface in areas where the glue has been printed, while the praseodymium colorant in areas without the glue printed is not bound by the glue and is recovered for future use. This allows the colorant to be applied using a digital glue positioning process. A dry granulation dispensing machine can be used for color application.

[0035] After the colorant is applied, a fan is used to remove the unadhered praseodymium colorant and recycle it. The amount of praseodymium colorant applied can be 150-200 g / m 2 If the amount of praseodymium pigment applied is too little, the green tone will be weak. If the amount of praseodymium pigment applied is too much, it will easily cause the glaze surface to be uneven.

[0036] The particle size of the praseodymium pigment is preferably controlled within 20-40 mesh. If the particle size of the praseodymium pigment is too small, the color of the bonding particles will not be obvious. If the particle size of the praseodymium pigment is too large, it will protrude from the glaze layer, causing glaze defects.

[0037] Apply dry granular glaze on the surface of the brick after applying praseodymium series colorant.

[0038] In some embodiments, the chemical composition of the dry granular glaze includes, by mass percentage, SiO2: 50%-61%, Al2O3: 9.5%-15%, Fe2O3: 0.05%-0.2%, CaO: 6.5%-12%, MgO: 0.85%-1.2%, K2O: 4.5%-6.3%, Na2O: 1.8%-2.2%, P2O5: 0.15%-0.3%, and ZnO: 5.5%-9.5%. Due to the low melting point of borosilicate glass, the silicon content of the dry granular glaze is controlled to 50%-61%, the aluminum content is controlled to 9.5%-15%, and the zinc content is controlled to 5.5%-9.5%. This improves the high-temperature fluidity of the dry granular glaze and prevents defects such as pores from forming during the fusion process between the praseodymium-based colorant and the dry granular glaze.

[0039] Preferably, the chemical composition of the dry granular glaze includes, by mass percentage, SiO2: 55%~60%, Al2O3: 10%~12%, Fe2O3: 0.05%~0.1%, CaO: 6.5%~12%, MgO: 0.85%~1.2%, K2O: 4.5%~6.3%, Na2O: 1.8%~2.2%, P2O5: 0.15%~0.3%, and ZnO: 8%~9.5%.

[0040] The dry granular glaze is applied by pouring glaze. Preferably, the specific gravity of the dry granular glaze is 1.45~1.55g / cm 3 , glaze application amount is 960~1100 g / m 2 By controlling the specific gravity and glaze application amount of the dry granular glaze within the above ranges, the flow rate and usage amount of the dry granular glaze can be reasonably controlled, so that the tile surface has an excellent three-dimensional effect and there are no obvious glaze defects on the tile surface.

[0041] The bricks after being applied with the dry granular glaze are dried.

[0042] The dried bricks are fed into the kiln. The firing atmosphere of the kiln is ammonia. The firing temperature is 1130-1180°C and the firing cycle is 40-45 minutes. By controlling the appropriate firing temperature and firing cycle, the discharge of pores can be promoted and the glaze surface can be ensured to be smooth. In particular, in a pure ammonia kiln, the main products of pure ammonia combustion are nitrogen and water, which is very important for Pr 3+ The main products of ammonia combustion as a fuel are nitrogen and water. Nitrogen is the primary product of flue gas during high-temperature firing, providing a protective atmosphere to a certain extent, preventing the conversion of +3 praseodymium ions to +4 and enhancing the green color. Furthermore, since ammonia combustion as a fuel primarily produces nitrogen and water, without producing carbon dioxide, it is considered a clean fuel that helps reduce greenhouse gas emissions.

[0043] Polishing and edge grinding give ceramic plate products.

[0044] In summary, the praseodymium-based pigment of the present invention features a unique core-shell structure of zirconium silicate particles encapsulated by a borosilicate glass phase. It is environmentally friendly and non-toxic, exhibiting excellent high-temperature resistance and chemical stability. This enhances the high-temperature stability of the praseodymium-based pigment, aiding in rapid glaze leveling and reducing the generation of bubbles during high-temperature firing, effectively improving product surface quality. Furthermore, the present invention, combined with the carbon-free nature of ammonia combustion, facilitates the production of new, environmentally friendly ceramic plate products.

[0045] The following examples are further listed to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific numerical values ​​exemplified below.

[0046] Example 1

[0047] Preparation of praseodymium pigments. According to the stoichiometric ratio of Pr x Zr 1-x Praseodymia, silica, and zirconium oxide are weighed in SiO4 (x = 0.07). Then, boron frit is added. After thorough grinding and dispersion, the mixture is dried to form a powder. The powder is then placed in a sagger, sintered at an appropriate temperature, and crushed into a desired particle size for later use. The chemical composition of the boron frit is as follows: Al2O3: 9.1%, SiO2: 38%, Fe2O3: 0.11%, CaO: 0.45%, K2O: 6.1%, Na2O: 15.7%, B2O3: 30.3%, and BaO: 0.24%. The amount of boron frit used is 5% of the total mass of praseodymia, silica, and zirconium oxide. The sintering temperature regime is as follows: first, heating to 1000°C, holding for 1.5 hours, then heating to 1350°C and holding for 2 hours.

[0048] Example 2

[0049] Preparation of praseodymium pigments. According to the stoichiometric ratio of Pr x Zr 1-xPraseodymia, silica, and zirconium oxide are weighed in SiO4 (x = 0.08). Then, boron frit is added. After thorough grinding and dispersion, the mixture is dried to form a powder. The powder is then placed in a sagger, sintered at an appropriate temperature, and crushed into a desired particle size for later use. The chemical composition of the boron frit is as follows: Al2O3: 9.3%, SiO2: 38%, Fe2O3: 0.09%, CaO: 0.42%, K2O: 5.95%, Na2O: 15.7%, B2O3: 30.3%, and BaO: 0.24%. The amount of boron frit used is 8% of the total mass of praseodymia, silica, and zirconium oxide. The sintering temperature regime is as follows: first, heating to 1000°C, holding for 1.5 hours, then heating to 1350°C and holding for 2 hours.

[0050] Example 3

[0051] Preparation of praseodymium pigments. According to the stoichiometric ratio of Pr x Zr 1-x Praseodymia, silica, and zirconium oxide are weighed in SiO4 (x = 0.06). Add boron frit, thoroughly grind and disperse, dry to form a powder, and place the powder in a sagger, sinter at an appropriate temperature, and crush to a desired particle size for later use. The boron frit's chemical composition, by mass percentage, is: 11.1% Al2O3, 35.2% SiO2, 0.15% Fe2O3, 0.36% CaO, 5.75% K2O, 15.2% Na2O, 32% B2O3, and 0.24% BaO. The amount of boron frit used is 3% of the total mass of praseodymia, silica, and zirconium oxide. The sintering temperature regime is: first, raise the temperature to 900°C, hold for 1 hour, then raise the temperature to 1250°C and hold for 1.5 hours.

[0052] Example 4

[0053] Preparation of praseodymium pigments. According to the stoichiometric ratio of Pr x Zr 1-x Praseodymia, silica, and zirconium oxide are weighed in SiO4 (x = 0.08). Then, boron frit is added. After thorough grinding and dispersion, the mixture is dried to form a powder. The powder is then placed in a sagger, sintered at an appropriate temperature, and crushed into a desired particle size for later use. The chemical composition of the boron frit is as follows: Al2O3: 9.2%, SiO2: 38.2%, Fe2O3: 0.12%, CaO: 0.45%, K2O: 5.95%, Na2O: 15.97%, B2O3: 29.8%, and BaO: 0.31%. The amount of boron frit used is 5% of the total mass of praseodymia, silica, and zirconium oxide. The sintering temperature regime is as follows: first, heating to 1000°C, holding for 1 hour, then heating to 1250°C, holding for 1.5 hours.

[0054] Comparative Example 1

[0055] The method is basically the same as Example 1, except that the amount of the boron frit used is 1% of the total mass of praseodymium oxide, silicon dioxide, and zirconium oxide.

[0056] Comparative Example 2

[0057] The method is basically the same as Example 1, with the only difference being that the sintering temperature regime is to first raise the temperature to 700° C. and keep the temperature for 1 hour, and then raise the temperature to 1100° C. and keep the temperature for 1.5 hours.

[0058] Figure 1 The following are images of the praseodymium-based pigments of Examples 1-2 and Comparative Examples 1-2 (from left to right, Examples 1-2 and Comparative Examples 1-2, respectively). It can be seen that the amount of boron frit used in Comparative Example 1 was relatively low, resulting in a yellow powder. The sintering temperature in Comparative Example 2 was relatively low, resulting in only a small amount of +4 praseodymium ions being converted to +3 praseodymium ions, resulting in a still yellowish color. Compared to the Comparative Examples, the Examples increased the amount of boron frit and the sintering temperature, resulting in a green praseodymium-based pigment.

[0059] Figure 2 This is a SEM image of the praseodymium-based pigment of Example 2. Figure 3 This is the XRD pattern of the praseodymium-based colorant of Example 2. It can be seen that the main crystalline phase of the sample is zirconium silicate, and there are also unreacted silicon oxide and zirconium oxide. XRD proves that the crystalline phase is zirconium silicate, and SEM proves that the zirconium silicate is encapsulated by the borosilicate glass phase. The combination of SEM and XRD results shows that a core-shell structure of borosilicate-encapsulated zirconium silicate has been formed. Since the main crystalline phase is zirconium silicate, the glass phase formed by the boron frit is borosilicate glass. In addition, the ionic radius of the trivalent praseodymium ion is much larger than that of the zirconium ion. Therefore, the trivalent praseodymium ion basically cannot exist in the zirconium silicate lattice and can only be in the borosilicate glass phase.

[0060] Example 5

[0061] A method for preparing a green decorative ceramic plate using a pure ammonia atmosphere comprises the following steps:

[0062] Step 1. Prepare a green brick: Press the green brick powder into a shape to obtain a green brick.

[0063] Step 2. Inkjet print a regular ink pattern on the brick surface.

[0064] Step 3. Position an inkjet-printed glue pattern on the brick surface after the inkjet-printed regular ink pattern. The grayscale of the glue pattern is 40%.

[0065] Step 4. Spread praseodymium pigment on the surface of the brick after positioning the inkjet printed glue pattern. x Zr 1-xPraseodymium oxide, silicon dioxide, and zirconium oxide are weighed in SiO4 (x = 0.07). Then, boron frit is added. After thorough grinding and dispersion, the powder is dried to form a powder. The powder is then placed in a sagger, sintered at an appropriate temperature, and crushed into a desired particle size for later use. The chemical composition of the boron frit is: by mass percentage, Al2O3: 9.1%, SiO2: 38%, Fe2O3: 0.11%, CaO: 0.45%, K2O: 6.1%, Na2O: 15.7%, B2O3: 30.3%, and BaO: 0.24%. The amount of boron frit used is 5% of the total mass of praseodymium oxide, silicon dioxide, and zirconium oxide. The sintering temperature is first raised to 1000°C, held for 1.5 hours, then raised to 1350°C and held for 2 hours. The particle size of the praseodymium pigment is 30 mesh.

[0066] Step 5. Apply dry granular glaze to the surface of the brick after spreading the praseodymium-based colorant. The chemical composition of the dry granular glaze includes, by mass percentage, SiO2: 60.5%, Al2O3: 11.5%, Fe2O3: 0.12%, CaO: 9.86%, MgO: 1.08%, K2O: 5.28%, Na2O: 2.18%, P2O5: 0.28%, and ZnO: 9.2%. The dry granular glaze is applied by pouring. The specific gravity of the dry granular glaze is 1.55g / cm 3 , the application amount is 1050g / m 2 .

[0067] Step 6. Place the dry granular glaze-coated bricks into a kiln for firing. The firing temperature is 1180° C., the firing cycle is 45 minutes, and the firing atmosphere in the kiln is ammonia.

[0068] Step 7. Polishing.

[0069] Figure 4 This is a brick surface effect diagram of the green decorative ceramic plate of Example 5. It can be seen that the ceramic plate sample presents a distinct green color, has an excellent three-dimensional effect, and has a smooth surface without obvious pores.

[0070] Comparative Example 3

[0071] A method for preparing a green decorative ceramic plate using a pure ammonia atmosphere comprises the following steps:

[0072] Step 1. Prepare a green brick: Press the green brick powder into a shape to obtain a green brick.

[0073] Step 2. Inkjet print a regular ink pattern on the brick surface.

[0074] Step 3. Position an inkjet-printed glue pattern on the surface of the brick after the inkjet-printed ordinary ink pattern. The grayscale of the glue pattern is 30%.

[0075] Step 4. Spread praseodymium pigment on the surface of the brick after positioning the inkjet printed glue pattern. x Zr 1-x Praseodymium oxide, silicon dioxide, and zirconium oxide are weighed in SiO4 (x = 0.07). Then, boron frit is added. After thorough grinding and dispersion, the powder is dried to form a powder. The powder is then placed in a sagger, sintered at an appropriate temperature, and crushed into a desired particle size for later use. The chemical composition of the boron frit is: by mass percentage, Al2O3: 9.1%, SiO2: 38%, Fe2O3: 0.11%, CaO: 0.45%, K2O: 6.1%, Na2O: 15.7%, B2O3: 30.3%, and BaO: 0.24%. The amount of boron frit used is 5% of the total mass of praseodymium oxide, silicon dioxide, and zirconium oxide. The sintering temperature is first raised to 1000°C, held for 1.5 hours, then raised to 1350°C and held for 2 hours. The particle size of the praseodymium pigment is 30 mesh.

[0076] Step 5. Apply dry granular glaze to the surface of the brick after the colorant has been applied. The chemical composition of the dry granular glaze includes, by mass percentage, SiO2: 62.9%, Al2O3: 7.5%, Fe2O3: 0.2%, CaO: 13.5%, MgO: 0.7%, K2O: 3.8%, Na2O: 6.4%, P2O5: 0.5%, and ZnO: 4.5%. The dry granular glaze is applied by pouring. The specific gravity of the dry granular glaze is 1.45g / cm 3 , the application amount is 1000g / m 2 .

[0077] Step 6. Place the dry granular glaze-coated bricks into a kiln for firing. The firing temperature is 1180° C., the firing cycle is 45 minutes, and the firing atmosphere in the kiln is ammonia.

[0078] Step 7. Polishing.

[0079] Figure 5 This is a brick surface effect picture of the decorative ceramic plate of Example 3. It can be seen that there are obvious white pores on the surface of the ceramic plate sample, and the overall color is dark.

[0080] Comparative Example 4

[0081] A method for preparing a green decorative ceramic plate using a pure ammonia atmosphere comprises the following steps:

[0082] Step 1. Prepare a green brick: Press the green brick powder into a shape to obtain a green brick.

[0083] Step 2. Inkjet print a regular ink pattern on the brick surface.

[0084] Step 3. Position an inkjet-printed glue pattern on the surface of the brick after the inkjet-printed ordinary ink pattern. The grayscale of the glue pattern is 30%.

[0085] Step 4. Spread praseodymium pigment on the surface of the brick after positioning the inkjet printed glue pattern. x Zr 1-x SiO4 (x = 0.08) weighs praseodymium oxide, silicon dioxide, and zirconium oxide, then adds boron frit. After thorough grinding and dispersion, dry the powder, place it in a sagger, sinter it at an appropriate temperature, and crush it into a desired particle size for later use. The chemical composition of the boron frit is: by mass percentage, Al2O3: 3.5%, SiO2: 41.3%, Fe2O3: 0.29%, CaO: 0.92%, K2O: 3.03%, Na2O: 8.5%, B2O3: 42%, and BaO: 0.46%. The amount of boron frit used is 8% of the total mass of praseodymium oxide, silicon dioxide, and zirconium oxide. The sintering temperature is first raised to 1000°C, held for 1.5 hours, then raised to 1350°C and held for 2 hours. The particle size of the praseodymium pigment is 30 mesh.

[0086] Step 5. Apply dry granular glaze to the surface of the brick after spreading the praseodymium-based colorant. The chemical composition of the dry granular glaze includes, by mass percentage, SiO2: 60.5%, Al2O3: 11.5%, Fe2O3: 0.12%, CaO: 9.86%, MgO: 1.08%, K2O: 5.28%, Na2O: 2.18%, P2O5: 0.28%, and ZnO: 9.2%. The dry granular glaze is applied by pouring. The specific gravity of the dry granular glaze is 1.55g / cm 3 , the application amount is 1050g / m 2 .

[0087] Step 6. Place the dry granular glaze-coated bricks into a kiln for firing. The firing temperature is 1180° C., the firing cycle is 45 minutes, and the firing atmosphere in the kiln is ammonia.

[0088] Step 7. Polishing.

[0089] In this comparative example, due to the improper chemical composition of the boron frit, although a core-shell structure of borosilicate glass encapsulating zirconium silicate is formed, it is easy to cause surface concave glaze defects.

Claims

1. A method for preparing a praseodymium-based colorant, characterized in that: The preparation method of the praseodymium series colorant comprises: x Zr 1- x Weigh praseodymium oxide, silicon dioxide, and zirconium oxide in the stoichiometric ratio of SiO4, then add boron frit, mix thoroughly, and dry to make powder; where 0<x ≤ 0.08; the powder is then sintered and crushed to obtain the praseodymium-based pigment; the chemical composition of the boron frit includes, by mass percentage, Al2O3: 7.8%-12%, SiO2: 30%-41%, Fe2O3: 0.05%-0.2%, CaO: 0.15%-0.5%, K2O: 5.5%-6.5%, Na2O: 14%-17%, B2O3: 28%-32%, and BaO: 0.15%-0.35%; the amount of the boron frit is 3%-8% of the total mass of praseodymium oxide, silicon dioxide, and zirconium oxide; the sintering includes: keeping warm at 900-1000°C for 1-2 hours, and then keeping warm at 1250-1350°C for 1.5-2.5 hours; the particle size of the praseodymium-based pigment is 20 mesh to 40 mesh.

2. A method for preparing green decorative ceramic panels using a pure ammonia atmosphere, characterized in that: The method comprises the following steps: Inkjet printing of ordinary ink patterns on the surface of the brick; Positioning an inkjet-printed glue pattern on the surface of the brick after the inkjet-printed conventional ink pattern; The praseodymium colorant obtained by the preparation method according to claim 1 is sprinkled on the surface of the brick after the inkjet printing glue pattern is positioned; the particle size of the praseodymium colorant is 20 mesh to 40 mesh; the application amount of the praseodymium colorant is 150 to 200 g / m 2 ; Applying a dry granular glaze on the surface of the brick after spreading the praseodymium-based colorant; the chemical composition of the dry granular glaze includes, by mass percentage, SiO2: 50%-61%, Al2O3: 9.5%-15%, Fe2O3: 0.05%-0.2%, CaO: 6.5%-12%, MgO: 0.85%-1.2%, K2O: 4.5%-6.3%, Na2O: 1.8%-2.2%, P2O5: 0.15%-0.3%, and ZnO: 5.5%-9.5%; The green decorative ceramic plate is obtained by firing and polishing the green brick after applying the dry granular glaze in a pure ammonia atmosphere.

3. The method according to claim 2, characterized in that The dry granular glaze is applied by pouring glaze; the specific gravity of the dry granular glaze is 1.45~1.55g / cm 3 , glaze application amount is 960~1100g / m 2 .

4. The method according to claim 2, characterized in that The grayscale of the glue pattern is 30% to 40%.

5. The method according to claim 2, characterized in that The firing temperature is 1130-1180° C., and the firing period is 40-45 minutes.

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