Heat reflection ceramic pigment as well as preparation method and application thereof

Abstract

The invention discloses a heat-reflecting ceramic pigment and a preparation method and application thereof, the chemical general formula of the heat-reflecting ceramic pigment is NdxCr1-xFeyTiO3.5 + 1.5 y, x is more than or equal to 0.15 and less than or equal to 0.45, and y is more than or equal to 0.5 and less than or equal to 0.7. According to the invention, equipotential substitution is formed through rare earth doping, and lattice distortion defects are formed by means of radius difference between ions, so that the ceramic pigment has relatively high reflectivity in visible-near infrared bands; meanwhile, the color of the pigment is adjusted by adopting Cr, so that the pigment is in a yellow system, and the beige heat-reflecting ceramic pigment is obtained. A loose and porous structure is formed in a precursor dehydration process by utilizing a foaming and puffing technology and adopting a nonionic foaming agent fatty acid ester, so that uniform dispersion of the ceramic pigment precursor is realized, and the influence of agglomeration of the precursor on poor dispersity of a sintered pigment is effectively solved, thereby improving the dispersity and heat reflection effect of the pigment.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic pigments, and in particular relates to a heat reflective ceramic pigment and a preparation method and application thereof. Background Art

[0002] Heating and cooling of buildings is one of the main causes of environmental problems such as the global greenhouse effect and the ozone hole. Therefore, building energy conservation has become a global concern. Traditionally, new wall materials such as aerated concrete blocks, hollow concrete blocks, porous fly ash bricks, and autoclaved fly ash bricks are used to achieve thermal insulation of building walls. However, a large number of studies have shown that the use of building exterior wall insulation technology is very effective in reducing heating energy consumption in northern regions, but the effect of reducing air conditioning and cooling energy consumption in southern regions is not obvious.

[0003] Using near-infrared reflective coatings on building exterior walls is an effective way to save energy. For reflective materials, white is the most common and easiest to prepare. For example, titanophene, zirconium oxide, aluminum oxide, calcium silicate, titanium dioxide, etc. all have high reflectivity. However, white is a single color and cannot meet people's demand for color, which limits its application. Beige is a common design for exterior wall decoration. Currently, there are many types of beige materials, but very few have high heat reflection.

[0004] Therefore, developing a beige ceramic colorant with good heat reflection effect has broad market prospects. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a heat-reflective ceramic colorant and a preparation method and application thereof, wherein the ceramic colorant is beige and has good heat-reflective effect in the visible-near infrared band.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a heat reflective ceramic pigment, the chemical formula of which is Nd x Cr 1-x Fe y TiO 3.5+1.5y , where: 0.15≤x≤0.45, 0.5≤y≤0.7.

[0007] Specifically, rare earth and transition metal ions have variable electronic structures, and thus have unique effects in the field of light and heat. The present invention forms equipotential substitution by rare earth doping, and forms lattice distortion defects by means of radius differences between ions, thereby achieving a ceramic pigment with a high reflectivity in the visible-near infrared band; at the same time, Cr is used to adjust the color of the pigment, making the pigment yellow, thereby obtaining a beige heat-reflective ceramic pigment.

[0008] In some embodiments of the present invention, the maximum particle size of the heat reflective ceramic pigment is no more than 20 μm. Fine-particle ceramic pigments have higher activity, which is beneficial to improving not only the coloring effect of the pigment, but also the heat reflective effect of the pigment.

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

[0010] (1) dissolving butyl titanate in anhydrous ethanol to obtain solution A;

[0011] (2) adding a soluble iron salt, a soluble chromium salt and a soluble neodymium salt to the solution A in a stoichiometric ratio according to the chemical formula, and mixing the mixture to obtain a solution B;

[0012] (3) adding citric acid to the solution B and mixing to obtain solution C;

[0013] (4) heating the solution C in a water bath, adding fatty acid ester, continuously stirring, emulsifying and foaming, and drying to obtain a puffed precursor;

[0014] (5) Grinding, calcining, grinding again, and sieving the precursor to obtain the heat reflective ceramic colorant.

[0015] Specifically, during the preparation of the precursor, due to gradual evaporation and dehydration, the precursor will condense into a hard block, which is difficult to break. At the same time, the powder after firing is also easy to form a large hard agglomeration, thereby affecting the performance of the colorant. The present invention uses foaming and expansion technology and adopts non-ionic foaming agent fatty acid ester to form a loose and porous structure during the dehydration process of the precursor, so that the precursor is evenly dispersed, thereby ensuring the dispersibility of the colorant after calcination and improving the reflective effect of the colorant.

[0016] In some embodiments of the present invention, in step (2), the concentration of solution A is 0.1-0.5 mol / L. Preferably, the concentration of solution A is 0.1-0.2 mol / L.

[0017] In some embodiments of the present invention, in step (2), the soluble iron salt is a nitrate, sulfate or hydrochloride of iron, for example, ferric nitrate, ferric sulfate, ferric chloride, etc.; preferably ferric nitrate.

[0018] In some embodiments of the present invention, in step (2), the soluble chromium salt is a nitrate, sulfate or hydrochloride of chromium, for example, chromium nitrate, chromium sulfate, chromium chloride, etc.; preferably, it is chromium nitrate.

[0019] In some embodiments of the present invention, in step (2), the soluble neodymium salt is a nitrate, sulfate or hydrochloride of neodymium, for example, neodymium nitrate, neodymium sulfate, neodymium chloride, etc.; preferably, neodymium nitrate.

[0020] In some embodiments of the present invention, in step (3), the amount of citric acid added is not less than 3 times the amount of butyl titanate.

[0021] In some embodiments of the present invention, in step (3), the amount of citric acid added is 3-4 times the amount of butyl titanate.

[0022] In some embodiments of the present invention, in step (4), the amount of the fatty acid ester added is 1-3 wt % of the anhydrous ethanol.

[0023] In some embodiments of the present invention, in step (4), the water bath heating temperature is 85-90°C.

[0024] In some embodiments of the present invention, in step (5), the maximum calcination temperature is 1250-1300°C.

[0025] In some embodiments of the present invention, in step (5), the holding time at the highest temperature is 30-90 minutes.

[0026] 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 above-mentioned heat-reflective ceramic colorant, or include the heat-reflective ceramic colorant prepared by the above-mentioned preparation method.

[0027] Compared with the prior art, the above technical solution of the present invention has at least the following technical effects or advantages:

[0028] (1) The present invention forms equipotential substitution by rare earth doping and forms lattice distortion defects by means of radius differences between ions, thereby achieving a ceramic pigment having a high reflectivity in the visible-near infrared band; at the same time, Cr is used to adjust the color of the pigment to make the pigment yellow, thereby obtaining a beige heat-reflective ceramic pigment.

[0029] (2) The present invention utilizes foaming and expansion technology and adopts non-ionic foaming agent fatty acid ester to form a loose and porous structure during the dehydration process of the precursor, thereby achieving uniform dispersion of the ceramic colorant precursor and effectively solving the effect of precursor agglomeration on the poor dispersion of the fired colorant, thereby improving the dispersion and heat reflection effect of the colorant.

[0030] (3) The preparation method of the heat-reflective ceramic pigment of the present invention is simple in process and is conducive to industrial large-scale production. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the examples, so that the technical personnel of the relevant technical field can understand the present invention. It is necessary to point out here that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The non-essential improvements and adjustments made to the present invention by the skilled person in the relevant field according to the above invention content should still belong to the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods that are not mentioned in detail are all process steps or preparation methods known to those skilled in the art.

[0032] Example 1

[0033] A heat reflective ceramic pigment, the chemical formula of which is Nd 0.15 Cr 0.85 Fe 0.7 TiO 4.55 , the maximum particle size is not greater than 20 μm, the preparation method of the heat reflective ceramic colorant comprises the following steps:

[0034] (1) According to the chemical formula Nd 0.15 Cr 0.85 Fe 0.7 TiO 4.55 Weigh butyl titanate, ferric nitrate, chromium nitrate and neodymium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 500 mL of anhydrous ethanol, stir and mix, and obtain solution A;

[0035] (2) 0.07 mol of ferric nitrate, 0.085 mol of chromium nitrate and 0.015 mol of neodymium nitrate were added to solution A in sequence, and the mixture was stirred to obtain solution B;

[0036] (3) Add 0.35 mol of citric acid to solution B and stir to obtain solution C;

[0037] (4) placing the beaker of solution C in a water bath at 85° C., adding 4 g of fatty acid ester to solution C, and stirring continuously to emulsify and foam; when solution C gradually evaporates, stopping stirring, and continuing to heat in the water bath until dry, to obtain an expanded precursor;

[0038] (5) The precursor is ground, calcined at 1250° C. for 90 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat reflective ceramic colorant of this embodiment.

[0039] Example 2

[0040] A heat reflective ceramic pigment, the chemical formula of which is Nd 0.45 Cr 0.55 Fe 0.5 TiO 4.25, the maximum particle size is not greater than 20 μm, the preparation method of the heat reflective ceramic colorant comprises the following steps:

[0041] (1) According to the chemical formula Nd 0.45 Cr 0.55 Fe 0.5 TiO 4.25 Weigh butyl titanate, ferric nitrate, chromium nitrate and neodymium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 600 mL of anhydrous ethanol, stir and mix, and obtain solution A;

[0042] (2) Add 0.05 mol of ferric nitrate, 0.055 mol of chromium nitrate and 0.045 mol of neodymium nitrate to solution A in sequence, stir and mix, and obtain solution B;

[0043] (3) Add 0.4 mol of citric acid to solution B and stir to obtain solution C;

[0044] (4) placing the beaker of solution C in a 90° C. water bath, adding 10 g of fatty acid ester to solution C, and stirring continuously to emulsify and foam; when solution C gradually evaporates, stop stirring, and continue heating in the water bath until dry to obtain an expanded precursor;

[0045] (5) The precursor is ground, calcined at 1300° C. for 30 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat reflective ceramic colorant of this embodiment.

[0046] Example 3

[0047] A heat reflective ceramic pigment, the chemical formula of which is Nd 0.3 Cr 0.7 Fe 0.5 TiO 4.25 , the maximum particle size is not greater than 20 μm, the preparation method of the heat reflective ceramic colorant comprises the following steps:

[0048] (1) According to the chemical formula Nd 0.3 Cr 0.7 Fe 0.5 TiO 4.25 Weigh butyl titanate, ferric nitrate, chromium nitrate and neodymium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 500 mL of anhydrous ethanol, stir and mix, and obtain solution A;

[0049] (2) 0.05 mol of ferric nitrate, 0.07 mol of chromium nitrate and 0.03 mol of neodymium nitrate were added to solution A in sequence, and the mixture was stirred to obtain solution B;

[0050] (3) Add 0.3 mol of citric acid to solution B and stir to obtain solution C;

[0051] (4) placing the beaker of solution C in a water bath at 88° C., adding 6 g of fatty acid ester to solution C, and stirring continuously to emulsify and foam; when solution C gradually evaporates, stopping stirring, and continuing to heat in the water bath until dry, to obtain an expanded precursor;

[0052] (5) The precursor is ground, calcined at 1280° C. for 60 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat-reflective ceramic colorant of this embodiment.

[0053] Example 4

[0054] A heat reflective ceramic pigment, the chemical formula of which is Nd 0.3 Cr 0.7 Fe 0.6 TiO 4.4 , the maximum particle size is not greater than 20 μm, the preparation method of the heat reflective ceramic colorant comprises the following steps:

[0055] (1) According to the chemical formula Nd 0.3 Cr 0.7 Fe 0.6 TiO 4.4 Weigh butyl titanate, ferric nitrate, chromium nitrate and neodymium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 500 mL of anhydrous ethanol, stir and mix, and obtain solution A;

[0056] (2) 0.06 mol of ferric nitrate, 0.07 mol of chromium nitrate and 0.03 mol of neodymium nitrate were added to solution A in sequence, and the mixture was stirred to obtain solution B;

[0057] (3) Add 0.35 mol of citric acid to solution B and stir to obtain solution C;

[0058] (4) placing the beaker of solution C in a 90° C. water bath, adding 5 g of fatty acid ester to solution C, stirring continuously, and performing emulsification and foaming; when solution C gradually evaporates, stirring is stopped, and the water bath is continued to heat until dry, thereby obtaining an expanded precursor;

[0059] (5) The precursor is ground, calcined at 1250° C. for 72 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat reflective ceramic colorant of this embodiment.

[0060] Comparative Example 1

[0061] The main difference between Comparative Example 1 and Example 4 is that the chemical composition of the heat reflective ceramic pigment does not contain Nd, and its chemical formula is CrFe 0.6 TiO 4.4 , the maximum particle size is not greater than 20 μm, the preparation method of the heat reflective ceramic colorant comprises the following steps:

[0062] (1) According to the chemical formula Nd 0.3 Cr 0.7 Fe 0.6 TiO 4.4 Weigh butyl titanate, ferric nitrate and chromium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 500 mL of anhydrous ethanol, stir and mix, to obtain solution A;

[0063] (2) Add 0.06 mol of ferric nitrate and 0.1 mol of chromium nitrate to solution A in sequence, stir and mix, to obtain solution B;

[0064] (3) Add 0.35 mol of citric acid to solution B and stir to obtain solution C;

[0065] (4) placing the beaker of solution C in a 90° C. water bath, adding 5 g of fatty acid ester to solution C, stirring continuously, and performing emulsification and foaming; when solution C gradually evaporates, stirring is stopped, and the water bath is continued to heat until dry, thereby obtaining an expanded precursor;

[0066] (5) The precursor was ground, calcined at 1250° C. for 72 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat-reflective ceramic pigment of this comparative example.

[0067] Comparative Example 2

[0068] The main difference between Comparative Example 2 and Example 4 is that the Nd content in the chemical composition of the heat reflective ceramic pigment is higher, and its chemical formula is Nd 0.5 Cr 0.5 Fe 0.6 TiO 4.4 , the maximum particle size is not greater than 20 μm, the preparation method of the heat reflective ceramic colorant comprises the following steps:

[0069] (1) According to the chemical formula Nd 0.5 Cr 0.5 Fe 0.6 TiO 4.4 Weigh butyl titanate, ferric nitrate, chromium nitrate and neodymium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 500 mL of anhydrous ethanol, stir and mix, and obtain solution A;

[0070] (2) 0.06 mol of ferric nitrate, 0.05 mol of chromium nitrate and 0.05 mol of neodymium nitrate were added to solution A in sequence, and the mixture was stirred to obtain solution B;

[0071] (3) Add 0.35 mol of citric acid to solution B and stir to obtain solution C;

[0072] (4) placing the beaker of solution C in a 90° C. water bath, adding 5 g of fatty acid ester to solution C, stirring continuously, and performing emulsification and foaming; when solution C gradually evaporates, stirring is stopped, and the water bath is continued to heat until dry, thereby obtaining an expanded precursor;

[0073] (5) The precursor was ground, calcined at 1250° C. for 72 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat-reflective ceramic pigment of this comparative example.

[0074] Comparative Example 3

[0075] The main difference between Comparative Example 3 and Example 4 is that the Fe content in the chemical composition of the heat reflective ceramic pigment is lower, and its chemical formula is Nd 0.3 Cr 0.7 Fe 0.2 TiO 3.8 , the maximum particle size is not greater than 20 μm, the preparation method of the heat reflective ceramic colorant comprises the following steps:

[0076] (1) According to the chemical formula Nd 0.3 Cr 0.7 Fe 0.2 TiO 3.8 Weigh butyl titanate, ferric nitrate, chromium nitrate and neodymium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 500 mL of anhydrous ethanol, stir and mix, and obtain solution A;

[0077] (2) 0.02 mol of ferric nitrate, 0.07 mol of chromium nitrate and 0.03 mol of neodymium nitrate were added to solution A in sequence, and the mixture was stirred to obtain solution B;

[0078] (3) Add 0.35 mol of citric acid to solution B and stir to obtain solution C;

[0079] (4) placing the beaker of solution C in a 90° C. water bath, adding 5 g of fatty acid ester to solution C, stirring continuously, and performing emulsification and foaming; when solution C gradually evaporates, stirring is stopped, and the water bath is continued to heat until dry, thereby obtaining an expanded precursor;

[0080] (5) The precursor was ground, calcined at 1250° C. for 72 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat-reflective ceramic pigment of this comparative example.

[0081] Comparative Example 4

[0082] The difference between Comparative Example 4 and Example 4 is that the content of Fe in the chemical composition of the heat reflective ceramic pigment is higher, and its chemical formula is Nd 0.3 Cr 0.7 FeTiO5, with a maximum particle size of no more than 20 μm, the preparation method of the heat reflective ceramic pigment comprises the following steps:

[0083] (1) According to the chemical formula Nd 0.3 Cr 0.7 FeTiO5 Weigh butyl titanate, ferric nitrate, chromium nitrate and neodymium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 500 mL of anhydrous ethanol, stir and mix to obtain solution A;

[0084] (2) 0.1 mol of ferric nitrate, 0.07 mol of chromium nitrate and 0.03 mol of neodymium nitrate were added to solution A in sequence, and the mixture was stirred to obtain solution B;

[0085] (3) Add 0.35 mol of citric acid to solution B and stir to obtain solution C;

[0086] (4) placing the beaker of solution C in a 90° C. water bath, adding 5 g of fatty acid ester to solution C, stirring continuously, and performing emulsification and foaming; when solution C gradually evaporates, stirring is stopped, and the water bath is continued to heat until dry, thereby obtaining an expanded precursor;

[0087] (5) The precursor was ground, calcined at 1250° C. for 72 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat-reflective ceramic pigment of this comparative example.

[0088] Comparative Example 5

[0089] The main difference between Comparative Example 5 and Example 4 is that no fatty acid ester is added during the preparation of the heat reflective ceramic pigment, and its chemical formula is Nd 0.3 Cr 0.7 Fe 0.6 TiO 4.4 , the maximum particle size is not greater than 20 μm, the preparation method of the heat reflective ceramic colorant comprises the following steps:

[0090] (1) According to the chemical formula Nd 0.3 Cr 0.7 Fe 0.6 TiO 4.4 Weigh butyl titanate, ferric nitrate, chromium nitrate and neodymium nitrate, first add 0.1 mol of butyl titanate into a beaker containing 500 mL of anhydrous ethanol, stir and mix, and obtain solution A;

[0091] (2) 0.06 mol of ferric nitrate, 0.07 mol of chromium nitrate and 0.03 mol of neodymium nitrate were added to solution A in sequence, and the mixture was stirred to obtain solution B;

[0092] (3) Add 0.35 mol of citric acid to solution B and stir to obtain solution C;

[0093] (4) Place the beaker containing solution C in a 90°C water bath and continue stirring. When solution C gradually evaporates, stop stirring and continue heating the water bath until it is dry to obtain a precursor.

[0094] (5) The precursor was ground, calcined at 1250° C. for 72 minutes, cooled and ground, and passed through a 500-mesh sieve to obtain the heat-reflective ceramic pigment of this comparative example.

[0095] Performance Testing

[0096] The thermal reflectivity of the thermal reflective ceramic pigment samples prepared in the above-mentioned Examples 1-4 and Comparative Examples 1-5 was tested. The testing process was as follows: the pigment was added to a common ceramic glaze (the addition amount was 5wt%), and the glaze was applied to the surface of a ceramic tile blank, and fired at 1200°C to obtain a ceramic tile; the thermal reflectivity of the glaze layer on the surface of the ceramic tile was tested. Wherein: the thermal reflectivity test was based on Part 1 of the standard GJB 5023.1A-2012 Test Method for Reflectivity and Emissivity of Materials and Coatings, and the test wavelength was 400-2500nm. The results are shown in Table 1.

[0097] Table 1:

[0098] sample Chemical formula Pigment dispersion Pigment color Reflectivity(%) Example 1 <![CDATA[Nd 0.15 Cr 0.85 Iron 0.7 TiO 4.55 ]]> Good dispersion, no agglomeration Beige 84 Example 2 <![CDATA[Nd 0.45 Cr 0.55 Iron 0.5 TiO 4.25 ]]> Good dispersion, no agglomeration Beige 85 Example 3 <![CDATA[Nd 0.3 Cr 0.7 Iron 0.5 TiO 4.25 ]]> Good dispersion, no agglomeration Beige 87 Example 4 <![CDATA[Nd 0.3 Cr 0.7 Iron 0.6 TiO 4.4 ]]> Good dispersion, no agglomeration Beige 86 Comparative Example 1 <![CDATA[CrFe 0.6 TiO 4.4 ]]> Good dispersion, no agglomeration Reddish brown 65 Comparative Example 2 <![CDATA[Nd 0.5 Cr 0.5 Iron 0.6 TiO 4.4 ]]> Good dispersion, no agglomeration Light Brown 72 Comparative Example 3 <![CDATA[Nd 0.3 Cr 0.7 Iron 0.2 TiO 3.8 ]]> Good dispersion, no agglomeration Brown 70 Comparative Example 4 <![CDATA[Nd 0.3 Cr 0.7 FeTiO5]]> Good dispersion, no agglomeration Light brown 65 Comparative Example 5 <![CDATA[Nd 0.3 Cr 0.7 Iron 0.6 TiO 4.4 ]]> Poor dispersibility and severe agglomeration Beige 72

[0099] As can be seen from Table 1, the ceramic pigments prepared in Examples 1-4 of the present invention have good dispersibility, no agglomeration, are beige in color, and have a reflectivity of 84-87%, and have good visible-near infrared light reflection effects.

[0100] Compared with Example 4, since the chemical composition of the ceramic pigment does not contain the Nd element, the color of the pigment is reddish brown and the reflectivity is significantly lower than that of Example 4.

[0101] Compared with Example 4, since the content of Nd or Fe in the chemical composition of the ceramic colorant is not within the protection scope of the present invention, the pigments of the colorant are light brown, brownish yellow and light brown, respectively, and the reflectivity is also lower than that of Example 4, indicating that the type and amount of doping elements have a great influence on the color and reflectivity of the colorant.

[0102] Comparative Example 5 Compared with Example 4, since no fatty acid ester was added during the preparation of the ceramic pigment, the dispersion of the pigment decreased and agglomeration was serious; although the pigment was beige, the reflectivity decreased significantly due to agglomeration.

[0103] For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, without having to go through creative labor. Therefore, simple improvements made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the protection scope of the present invention. The above embodiments are preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made should belong to the protection scope of the present invention.

Claims

1. A heat reflective ceramic pigment, characterized in that: The chemical formula of the heat reflective ceramic pigment is Nd x Cr 1- x Fe y TiO 3.5+1.5y , where: 0.15≤x≤0.45, 0.5≤y≤0.

7.

2. The heat reflective ceramic colorant according to claim 1, characterized in that: The maximum particle size of the heat reflective ceramic colorant is no more than 20 μm.

3. A method for preparing the heat reflective ceramic pigment according to claim 1 or 2, characterized in that: The following steps are involved: (1) dissolving butyl titanate in anhydrous ethanol to obtain solution A; (2) adding a soluble iron salt, a soluble chromium salt and a soluble neodymium salt to the solution A in a stoichiometric ratio according to the general chemical formula, and mixing the mixture to obtain a solution B; (3) adding citric acid to the solution B and mixing to obtain solution C; (4) heating the solution C in a water bath, adding fatty acid ester, continuously stirring, emulsifying and foaming, and drying to obtain a puffed precursor; (5) Grinding, calcining, grinding again, and sieving the precursor to obtain the heat reflective ceramic colorant.

4. The method for preparing the heat reflective ceramic pigment according to claim 3, characterized in that: In step (2), the concentration of solution A is 0.1-0.5 mol / L.

5. The method for preparing the heat reflective ceramic pigment according to claim 3, characterized in that: In step (2), the soluble iron salt is nitrate, sulfate or hydrochloride of iron; and / or the soluble chromium salt is nitrate, sulfate or hydrochloride of chromium; and / or the soluble neodymium salt is nitrate, sulfate or hydrochloride of neodymium.

6. The method for preparing the heat reflective ceramic pigment according to claim 3, characterized in that: In step (3), the amount of citric acid added is not less than 3 times the amount of butyl titanate.

7. The method for preparing the heat reflective ceramic pigment according to claim 3, characterized in that: In step (4), the amount of fatty acid ester added is 1-3wt% of anhydrous ethanol.

8. The method for preparing the heat reflective ceramic pigment according to claim 3, characterized in that: In step (4), the water bath heating temperature is 85-90°C.

9. The method for preparing the heat reflective ceramic pigment according to claim 3, characterized in that: In step (5), the maximum calcination temperature is 1250-1300° C.; and / or the holding time at the maximum temperature is 30-90 minutes.

10. An exterior wall ceramic tile, characterized in that: The raw materials for preparing the exterior wall ceramic tiles include the heat-reflective ceramic colorant as described in claim 1 or 2, or include the heat-reflective ceramic colorant prepared by any preparation method as claimed in any one of claims 3-9.