A heat-reflecting brown ceramic colorant, a preparation method and application thereof

Abstract

The application belongs to the technical field of ceramic pigments, and particularly discloses a heat-reflecting brown ceramic pigment, a preparation method and application thereof. 1‑x (Li,Fe) x TiSiO5, wherein 0.1<=x<=0.4. The application is based on a stable titanium sphene crystal phase, and trivalent coloring ions Fe 3+ and monovalent Li + are co-doped in a molar ratio of 1:1, Ca 2+ in the titanium sphene structure is replaced by the composite ions, a brown titanium sphene pigment with a stable structure is formed, effective coloring of the titanium sphene is realized on the premise of retaining high reflectivity of the titanium sphene, the reflectivity of the pigment in the visible-near infrared band can reach 86-90%, and meanwhile, in the preparation, a method of ball milling followed by superfine grinding is adopted to improve the reactivity of the raw materials in the refining process by mechanical chemical action, and the color development and heat color reflection effect of the pigment are further improved.

Description

Technical Field

[0001] This invention belongs to the field of ceramic pigment technology, specifically relating to a heat-reflective brown ceramic pigment, its preparation method, and its application. Background Technology

[0002] With the advancement of the "dual-carbon" policy, various industries have launched a wave of energy conservation and carbon reduction initiatives. Given my country's massive building volume, building energy conservation is a key area of ​​concern. In hot regions, indoor air conditioning energy consumption is consistently a major energy consumer; therefore, reducing air conditioning energy consumption is a crucial direction for building energy conservation.

[0003] Heat-reflective materials can effectively reduce the heat transferred from the visible to near-infrared bands of sunlight to building surfaces, making them a crucial direction for building energy conservation. Simultaneously, building exteriors require decorative appeal, thus highly reflective pigments have a promising market prospect. White reflective materials are the most common and easiest to prepare; for example, titanium sphene (CaTiSiO5), zirconium oxide, alumina, calcium silicate, and titanium dioxide all possess good reflective properties. Among these, titanium sphene has the highest reflectivity, but its pure white color results in poor decorative effects. Brown is a common design choice for exterior wall decoration, and while there are many types of brown pigments available, those with high heat reflectivity are extremely rare.

[0004] Therefore, developing a brown ceramic pigment with good heat reflection effect has broad market prospects. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a heat-reflective brown ceramic pigment, its preparation method, and its application. The ceramic pigment is brown and has good heat reflection effects in the visible-near infrared band.

[0006] To address the aforementioned technical problems, a first aspect of the present invention provides a heat-reflective brown ceramic pigment, wherein the general chemical formula of the heat-reflective brown ceramic pigment is Ca. 1-x (Li,Fe) x TiSiO5, where 0.1≤x≤0.4.

[0007] Specifically, some colored rare earth oxides and transition metal ion oxides can be directly used as low-temperature colorants in fields such as paints and plastics. However, for ceramic colorants, because they require high-temperature firing during application, these metal oxides usually struggle to achieve good color development. This invention is based on a stable titanium sphene crystal phase and utilizes trivalent coloring ions (Fe...) 3+ Doping to replace divalent Ca in titanium sphene 2+The colored ions are doped into the crystal structure of titanium sphene, forming colored titanium sphene without altering its crystal form, thus preserving its high reflectivity. However, due to the presence of Fe ions... 3+ The valence state is higher than Ca 2+ Direct doping would lead to a decrease in the stability of the titanium sphene crystal structure. Therefore, this invention utilizes low-valence Li... + with Fe 3+ Co-doping was performed at a molar ratio of 1:1 to improve the stability of the doped titanite crystal structure without causing Fe... 3+ It exists in pigments in the form of iron oxide.

[0008] In some embodiments of the present invention, the maximum particle size of the heat-reflective brown ceramic pigment is no greater than 20 μm. Fine-particle-size ceramic pigments have higher activity, which not only improves the color development effect of the pigment but also enhances its heat-reflective properties.

[0009] A second aspect of the present invention provides a method for preparing the above-mentioned heat-reflective brown ceramic pigment, comprising the following steps:

[0010] (1) Weigh calcium carbonate, titanium oxide, silicon oxide, lithium carbonate and iron oxide according to the stoichiometric ratio of the general chemical formula, add water and mix to obtain slurry A;

[0011] (2) Grind the slurry A to obtain slurry C;

[0012] (3) Spray dry the slurry C to obtain powder;

[0013] (4) The powder is calcined, cooled, ground and sieved to obtain the heat-reflective brown ceramic pigment.

[0014] In some embodiments of the present invention, in step (1), the solid content of the slurry A is 35-55 wt%.

[0015] In some embodiments of the present invention, in step (2), the preparation step of the slurry C is as follows: first, slurry A is ball-milled to obtain slurry B; then, a grinding aid is added to slurry B for ultrafine grinding to obtain slurry C.

[0016] In some embodiments of the present invention, the maximum particle size of slurry B is not higher than 10 μm, and the average particle size of slurry C is not higher than 200 nm.

[0017] Specifically, in the preparation of the heat-reflective brown ceramic pigment of the present invention, slurry A is first ball-milled into slurry B with micron-sized particles; then, slurry B is ultra-finely ground using high-energy grinding technology to obtain slurry C with nano-sized particles; the reactivity of the raw materials in the refining process is improved by means of mechanochemical action to further improve the color development and heat reflection effect of the pigment.

[0018] In some embodiments of the present invention, the grinding aid includes triethanolamine, and the amount of triethanolamine added is 0.3-0.5 wt% of the solid raw material in slurry B. Adding a certain amount of grinding aid is beneficial to improving the efficiency of ultrafine grinding.

[0019] In some embodiments of the present invention, the grinding balls used in the ball mill are zirconia balls.

[0020] In some embodiments of the present invention, the grinding balls for ultrafine grinding are 0.3-0.5 mm zirconia beads.

[0021] In some embodiments of the present invention, in step (3), the temperature of the spray drying is 120-135°C.

[0022] In some embodiments of the present invention, in step (4), the maximum calcination temperature is 1250-1350°C.

[0023] In some embodiments of the present invention, in step (4), the heat preservation time at the highest temperature is 1-3 hours.

[0024] A third aspect of the present invention provides an exterior wall ceramic tile, wherein the raw materials for preparing the exterior wall ceramic tile include the heat-reflective brown ceramic pigment as described above, or include the heat-reflective brown ceramic pigment prepared by the preparation method described above.

[0025] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages:

[0026] (1) This invention is based on a stable titanium sphene crystal phase and uses trivalent coloring ions Fe 3+ and monovalent Li + Co-doping was performed at a molar ratio of 1:1, and the Ca in the titanium sphene structure was affected by the composite ions. 2+ Equivalent substitution is used to form a brown titanium sphene pigment with a stable structure. While retaining the high reflectivity of titanium sphene, effective coloring of titanium sphene is achieved. The reflectivity of the pigment in the visible-near infrared band can reach 86-90%.

[0027] (2) In the preparation of the heat-reflective brown ceramic pigment of the present invention, ball milling followed by ultrafine grinding is adopted. The mechanical chemical action is used to improve the reactivity of the raw materials in the refining process, thereby further improving the color development and heat reflection effect of the pigment.

[0028] (3) The method for preparing heat-reflective brown ceramic pigment of the present invention is simple and conducive to large-scale industrial production. Attached Figure Description

[0029] Figure 1 The XRD pattern of the heat-reflective brown ceramic pigment prepared in Example 1 of this invention. Detailed Implementation

[0030] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0031] Example 1

[0032] A heat-reflective brown ceramic pigment with the chemical formula Ca 0.9 (Li,Fe) 0.1 The preparation method of this heat-reflective brown ceramic pigment, TiSiO5 with a maximum particle size of no more than 20 μm, includes the following steps:

[0033] (1) According to the chemical formula Ca 0.9 (Li,Fe) 0.1 0.9 mol of calcium carbonate, 1 mol of titanium dioxide, 1 mol of silicon dioxide, 0.1 mol of lithium carbonate and 0.1 mol of iron oxide were weighed out of TiSiO5, added to water and stirred to form slurry A with a solid content of 35 wt%.

[0034] (2) Slurry A is fed into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm; then triethanolamine (0.3 wt% of the total mass of raw materials) is added to slurry B and then fed into a nano mill for ultrafine grinding. The grinding balls in the mill are 0.3-0.5 mm zirconia beads to obtain slurry C with an average particle size of no more than 200 nm.

[0035] (3) Spray dry the slurry C at a hot air temperature of 135°C to obtain a dispersed dry powder.

[0036] (4) The dispersed dry powder is loaded into an alumina sagger and calcined at 1350°C for 1.5 hours. After cooling and grinding, it is passed through a 500-mesh sieve to obtain the heat-reflective brown ceramic pigment of this embodiment.

[0037] Figure 1 The XRD pattern of the heat-reflective brown ceramic pigment prepared in Example 1 is shown below. Figure 1 It can be seen that the pigment has a titanite crystal form, and no other crystal diffraction peaks were observed, indicating that the doped Fe... 3+ and Li + It has entered the crystal lattice structure of titanite, replacing some of the Ca. 2+ It has a stable titanium sphene structure.

[0038] Example 2

[0039] A heat-reflective brown ceramic pigment with the chemical formula Ca 0.8 (Li,Fe) 0.2 The preparation method of this heat-reflective brown ceramic pigment, TiSiO5 with a maximum particle size of no more than 20 μm, includes the following steps:

[0040] (1) According to the chemical formula Ca 0.8 (Li,Fe) 0.2 0.8 mol of calcium carbonate, 1 mol of titanium dioxide, 1 mol of silicon dioxide, 0.2 mol of lithium carbonate and 0.2 mol of iron oxide were weighed out of TiSiO5, added to water and stirred to form slurry A with a solid content of 55 wt%.

[0041] (2) Slurry A is introduced into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm; then triethanolamine (0.5 wt% of the total mass of raw materials) is added to slurry B and then introduced into a nano mill for ultrafine grinding. The grinding balls in the mill are 0.3-0.5 mm zirconia beads to obtain slurry C with an average particle size of no more than 200 nm.

[0042] (3) Spray dry the slurry C at a hot air temperature of 120°C to obtain a dispersed dry powder.

[0043] (4) The dispersed dry powder is loaded into an alumina sagger and calcined at 1250°C for 3 hours. After cooling and grinding, it is passed through a 500-mesh sieve to obtain the heat-reflective brown ceramic pigment of this embodiment.

[0044] Example 3

[0045] A heat-reflective brown ceramic pigment with the chemical formula Ca 0.7 (Li,Fe) 0.3 The preparation method of this heat-reflective brown ceramic pigment, TiSiO5 with a maximum particle size of no more than 20 μm, includes the following steps:

[0046] (1) According to the chemical formula Ca 0.7 (Li,Fe) 0.30.7 mol of calcium carbonate, 1 mol of titanium dioxide, 1 mol of silicon dioxide, 0.3 mol of lithium carbonate and 0.3 mol of iron oxide were weighed out of TiSiO5, added to water and stirred to form slurry A with a solid content of 40 wt%.

[0047] (2) Slurry A is fed into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm; then triethanolamine (0.4 wt% of the total mass of raw materials) is added to slurry B and then fed into a nano mill for ultrafine grinding. The grinding balls in the mill are 0.3-0.5 mm zirconia beads to obtain slurry C with an average particle size of no more than 200 nm.

[0048] (3) Spray dry the slurry C at a hot air temperature of 130°C to obtain a dispersed dry powder.

[0049] (4) The dispersed dry powder is loaded into an alumina sagger and calcined at 1300°C for 2 hours. After cooling and grinding, it is passed through a 500-mesh sieve to obtain the heat-reflective brown ceramic pigment of this embodiment.

[0050] Example 4

[0051] A heat-reflective brown ceramic pigment with the chemical formula Ca 0.6 (Li,Fe) 0.4 The preparation method of this heat-reflective brown ceramic pigment, TiSiO5 with a maximum particle size of no more than 20 μm, includes the following steps:

[0052] (1) According to the chemical formula Ca 0.6 (Li,Fe) 0.4 0.6 mol of calcium carbonate, 1 mol of titanium dioxide, 1 mol of silicon dioxide, 0.4 mol of lithium carbonate and 0.4 mol of iron oxide were weighed out of TiSiO5, added to water and stirred to form slurry A with a solid content of 45 wt%.

[0053] (2) Slurry A is introduced into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm; then triethanolamine (0.5 wt% of the total mass of raw materials) is added to slurry B and then introduced into a nano mill for ultrafine grinding. The grinding balls in the mill are 0.3-0.5 mm zirconia beads to obtain slurry C with an average particle size of no more than 200 nm.

[0054] (3) Spray dry the slurry C at a hot air temperature of 120°C to obtain a dispersed dry powder.

[0055] (4) The dispersed dry powder is loaded into an alumina sagger and calcined at 1250°C for 3 hours. After cooling and grinding, it is passed through a 500-mesh sieve to obtain the heat-reflective brown ceramic pigment of this embodiment.

[0056] Comparative Example 1

[0057] The main difference between Comparative Example 1 and Example 4 lies in the higher content of Fe and Li in the chemical composition of the heat-reflective ceramic pigment, whose chemical formula is Ca. 0.2 (Li,Fe) 0.8 The preparation method of this heat-reflective ceramic colorant, TiSiO5 with a maximum particle size of no more than 20 μm, includes the following steps:

[0058] (1) According to the chemical formula Ca 0.2 (Li,Fe) 0.8 0.2 mol of calcium carbonate, 1 mol of titanium dioxide, 1 mol of silicon dioxide, 0.8 mol of lithium carbonate and 0.8 mol of iron oxide were weighed out of TiSiO5, added to water and stirred to form slurry A with a solid content of 45 wt%.

[0059] (2) Slurry A is introduced into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm; then triethanolamine (0.5 wt% of the total mass of raw materials) is added to slurry B and then introduced into a nano mill for ultrafine grinding. The grinding balls in the mill are 0.3-0.5 mm zirconia beads to obtain slurry C with an average particle size of no more than 200 nm.

[0060] (3) Spray dry the slurry C at a hot air temperature of 120°C to obtain a dispersed dry powder.

[0061] (4) The dispersed dry powder is loaded into an alumina sagger and calcined at 1250℃ for 3 hours. After cooling and grinding, it is passed through a 500-mesh sieve to obtain the heat-reflective ceramic colorant of this comparative example.

[0062] Comparative Example 2

[0063] The main difference between Comparative Example 2 and Example 4 lies in the lower content of Fe and Li in the chemical composition of the heat-reflective ceramic pigment, whose chemical formula is Ca. 0.95 (Li,Fe) 0.05 The preparation method of this heat-reflective ceramic colorant, TiSiO5 with a maximum particle size of no more than 20 μm, includes the following steps:

[0064] (1) According to the chemical formula Ca 0.95 (Li,Fe) 0.05 0.95 mol of calcium carbonate, 1 mol of titanium dioxide, 1 mol of silicon dioxide, 0.05 mol of lithium carbonate and 0.05 mol of iron oxide were weighed out of TiSiO5, added to water and stirred to form slurry A with a solid content of 45 wt%.

[0065] (2) Slurry A is introduced into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm; then triethanolamine (0.5 wt% of the total mass of raw materials) is added to slurry B and then introduced into a nano mill for ultrafine grinding. The grinding balls in the mill are 0.3-0.5 mm zirconia beads to obtain slurry C with an average particle size of no more than 200 nm.

[0066] (3) Spray dry the slurry C at a hot air temperature of 120°C to obtain a dispersed dry powder.

[0067] (4) The dispersed dry powder is loaded into an alumina sagger and calcined at 1250℃ for 3 hours. After cooling and grinding, it is passed through a 500-mesh sieve to obtain the heat-reflective ceramic colorant of this comparative example.

[0068] Comparative Example 3

[0069] The main difference between Comparative Example 2 and Example 4 is that the heat-reflective ceramic pigment does not contain Fe and Li in its chemical composition, and its chemical formula is CaTiSiO5 with a maximum particle size of no more than 20 μm. The preparation method of this heat-reflective ceramic pigment includes the following steps:

[0070] (1) According to the chemical formula Ca 0.95 (Li,Fe) 0.05 1 mol of calcium carbonate, 1 mol of titanium dioxide, and 1 mol of silicon dioxide were weighed out and added to water and stirred to form slurry A with a solid content of 45 wt%.

[0071] (2) Slurry A is introduced into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm; then triethanolamine (0.5 wt% of the total mass of raw materials) is added to slurry B and then introduced into a nano mill for ultrafine grinding. The grinding balls in the mill are 0.3-0.5 mm zirconia beads to obtain slurry C with an average particle size of no more than 200 nm.

[0072] (3) Spray dry the slurry C at a hot air temperature of 120°C to obtain a dispersed dry powder.

[0073] (4) The dispersed dry powder is loaded into an alumina sagger and calcined at 1250℃ for 3 hours. After cooling and grinding, it is passed through a 500-mesh sieve to obtain the heat-reflective ceramic colorant of this comparative example.

[0074] Comparative Example 4

[0075] The main difference between Comparative Example 4 and Example 4 is that the heat-reflective ceramic pigment does not contain Li in its chemical composition; its chemical composition is Ca. 0.6 Fe 0.4The preparation method of this heat-reflective ceramic colorant, TiSiO5 with a maximum particle size of no more than 20 μm, includes the following steps:

[0076] (1) Weigh out 0.6 mol of calcium carbonate, 1 mol of titanium dioxide, 1 mol of silicon dioxide and 0.4 mol of iron oxide respectively, add them to water and stir to form slurry A with a solid content of 45 wt%;

[0077] (2) Slurry A is introduced into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm; then triethanolamine (0.5 wt% of the total mass of raw materials) is added to slurry B and then introduced into a nano mill for ultrafine grinding. The grinding balls in the mill are 0.3-0.5 mm zirconia beads to obtain slurry C with an average particle size of no more than 200 nm.

[0078] (3) Spray dry the slurry C at a hot air temperature of 120°C to obtain a dispersed dry powder.

[0079] (4) The dispersed dry powder is loaded into an alumina sagger and calcined at 1250℃ for 3 hours. After cooling and grinding, it is passed through a 500-mesh sieve to obtain the heat-reflective ceramic colorant of this comparative example.

[0080] Comparative Example 5

[0081] The main difference between Comparative Example 5 and Example 4 is that the heat-reflective ceramic pigment is directly ball-milled during preparation, and its chemical formula is Ca. 0.6 (Li,Fe) 0.4 The preparation method of this heat-reflective ceramic colorant, TiSiO5 with a maximum particle size of no more than 20 μm, includes the following steps:

[0082] (1) According to the chemical formula Ca 0.6 (Li,Fe) 0.4 0.6 mol of calcium carbonate, 1 mol of titanium dioxide, 1 mol of silicon dioxide, 0.4 mol of lithium carbonate and 0.4 mol of iron oxide were weighed out of TiSiO5, added to water and stirred to form slurry A with a solid content of 45 wt%.

[0083] (2) The slurry A is fed into a ball mill containing zirconia balls for ball milling to obtain slurry B with a maximum particle size of no more than 10 μm;

[0084] (3) Spray dry slurry B at a hot air temperature of 120°C to obtain a dispersed dry powder.

[0085] (4) The dispersed dry powder was placed in an alumina crucible and calcined at 1250℃ for 3 hours. After cooling and grinding, the powder was passed through a 500-mesh sieve to obtain the heat-reflective ceramic colorant of this comparative example. Performance Testing

[0086] The phase composition and thermal reflectance properties of the thermochromic ceramic pigment samples prepared in Examples 1-4 and Comparative Examples 1-5 were tested. The testing procedure was as follows: the pigment was added to ordinary ceramic glaze (addition amount of 5 wt%), and the glaze was applied to the surface of the ceramic tile blank and fired at 1200℃ to obtain ceramic tiles; the thermal reflectance of the glaze layer on the surface of the ceramic tile was tested. Specifically, the thermal reflectance was tested according to Part 1 of standard GJB 5023.1A-2012, Test Methods for Reflectivity and Emissivity of Materials and Coatings, with a test wavelength of 400-2500 nm; the phase composition was determined by XRD. The results are shown in Table 1.

[0087] Table 1:

[0088]

[0089] As shown in Table 1, the ceramic pigments prepared in Examples 1-4 of the present invention have a stable titanium sphene crystal form, are brown in color, and have a reflectivity of 86-90%, exhibiting good reflectivity for visible and near-infrared light.

[0090] Compared to Example 4, Comparative Example 1 shows a reddish-brown color and a significantly lower reflectance than Example 4 because the doping of Li and Fe in the chemical composition of the ceramic pigment is too high and a certain amount of iron oxide is present in the phase.

[0091] Compared to Example 4, Comparative Examples 2-3 all had a white color because the doping levels of Li and Fe in the chemical composition of the ceramic pigments were too low or they did not contain Li and Fe.

[0092] Compared to Example 4, Comparative Example 4 does not contain Li in its ceramic pigment chemical composition, but has Fe doping ions. 3+ The valence state is higher than Ca 2+ This results in unstable crystal structure of titanium sphene, with Fe2O3 as the main coloring material. Therefore, the color of the pigment is reddish-brown, and its reflectivity is not as good as that of Example 4.

[0093] Compared to Example 4, Comparative Example 5 shows that the ceramic pigment was not ultra-finely ground during preparation, resulting in a low synthesis rate of titanium sphene during high-temperature firing. Consequently, the pigment is reddish-brown in color and has a lower reflectivity.

[0094] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A heat-reflective brown ceramic pigment, characterized in that, The chemical formula of the heat-reflective brown ceramic pigment is Ca. 1-x (Li,Fe) x TiSiO5, where 0.1 ≤ x ≤ 0.4; The heat-reflective brown ceramic pigment is prepared by a method including the following steps: (1) Weigh calcium carbonate, titanium oxide, silicon oxide, lithium carbonate and iron oxide according to the stoichiometric ratio of the general chemical formula, add water and mix to obtain slurry A; (2) The slurry A is ball-milled to obtain slurry B; then a grinding aid is added to the slurry B for ultrafine grinding to obtain slurry C; The maximum particle size of slurry B is not higher than 10 μm, and the average particle size of slurry C is not higher than 200 nm. The grinding aid includes triethanolamine, and the amount of triethanolamine added is 0.3-0.5 wt% of the solid raw materials in slurry B; (3) Spray dry the slurry C to obtain powder; (4) The powder is calcined, cooled, ground and sieved to obtain the heat-reflective brown ceramic pigment.

2. The heat-reflective brown ceramic pigment according to claim 1, characterized in that, The maximum particle size of the heat-reflective brown ceramic pigment is no greater than 20 μm.

3. The heat-reflective brown ceramic pigment according to claim 1, characterized in that, In step (1), the solid content of the slurry A is 35-55 wt%.

4. The heat-reflective brown ceramic pigment according to claim 1, characterized in that, In step (3), the spray drying temperature is 120-135℃.

5. The heat-reflective brown ceramic pigment according to claim 1, characterized in that, In step (4), the highest calcination temperature is 1250-1350℃; and / or, the holding time at the highest temperature is 1-3 hours.

6. An exterior wall ceramic tile, characterized in that, The raw materials for preparing the exterior wall ceramic tiles include the heat-reflective brown ceramic pigment as described in any one of claims 1-5.

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