High-temperature-resistant red fluorescent pigment for ceramics and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant red fluorescent pigment for ceramics and a preparation method thereof, the fluorescent pigment has a chemical general formula of (M1-xEux) S (0.001 < = x < = 0.05), M is Ca or Sr or a solid solution of Ca and Sr, and the valence of Eu is + 2. The obtained red fluorescent pigment can reflect red light with the wavelength of 600 nm or above, and can emit red light with the peak value located at 620-655 nm when excited by ultraviolet-visible light with the wavelength of 250-550 nm; the obtained red fluorescent pigment is bright in color and luster, high in color development power and good in medium-high temperature color development stability, and the chromatic value LAB of the red fluorescent pigment is almost not changed after the red fluorescent pigment is heated for 1 h in air at 500-750 DEG C; the red fluorescent pigment is synthesized through a solid phase, the preparation process is simple, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic pigments, and in particular relates to a high temperature resistant red fluorescent pigment for ceramics and a preparation method thereof. Background Art

[0002] Red is the most precious and freshest color in ceramic decoration. Red has a strong visual impact and decorative effect, and can provide sharp contrast and rich color levels in works of art. Therefore, red inorganic pigments have always been the research focus and hotspot in the field of inorganic pigments. Traditional red pigments mainly include iron red (main component Fe2O3), cadmium red (main component CdSeS), γ-Ce2S3, etc. However, Fe2O3 has the problem of low brightness and dark color. Although cadmium red has bright colors, it contains toxic elements, which limits its practical application. As a new type of non-toxic red pigment, γ-Ce2S3 has a bright deep red color and can be used with CdS x Se 1-x Colorants are comparable to red ceramic pigments, but they will be oxidized when sintered above 350°C in air, limiting their application in medium and high temperature fields. In summary, with the rapid development of the ceramic industry, especially in the application of high-end ceramic products and decorative ceramics, the performance requirements for pigments are getting higher and higher. Traditional red ceramic pigments have certain deficiencies in terms of color vividness, high temperature resistance and light stability, which limits their application effect in high-temperature firing and long-term use. With the increasingly stringent environmental protection regulations, the development of non-toxic and harmless fluorescent pigments for ceramics has become a research focus. Summary of the invention

[0003] The present invention aims to provide a method for preparing a high temperature resistant red fluorescent pigment for ceramics, which uses M compounds (M is strontium or calcium or strontium plus calcium), S powder, and europium compounds (such as Eu2O3, but not limited thereto) as raw materials, and synthesizes a series of new red inorganic fluorescent pigments with adjustable chromaticity by doping europium compounds or adding ammonium fluoride, potassium carbonate, sodium carbonate, lithium carbonate, and ammonium chloride as mineralizers according to a certain molar ratio.

[0004] To achieve the above object, the present invention adopts the following technical solution: The main component of the high temperature ceramic red fluorescent pigment of the present invention is (M 1-x Eu x )S, wherein M=Sr, Ca, or Sr+Ca, 0<x≤0.05. The preparation method is as follows: 1) Using M compound, S powder and europium compound as raw materials, weigh the raw materials respectively according to the stoichiometric ratio of each element in the above chemical formula, wherein the molar ratio of M compound to S powder is 1:2-1:6; The M compound is one or more of a carbonate containing M, an oxide containing M or a nitrate containing M, and more preferably a carbonate containing M, i.e. strontium carbonate or calcium carbonate. The europium compound is one or more of europium oxide, europium carbonate or europium nitrate, and more preferably europium oxide.

[0005] 2) Put the weighed raw materials into an agate mortar, add a mineralizer and grind and mix evenly; the mineralizer is one or more of ammonium fluoride, potassium carbonate, sodium carbonate, lithium carbonate or ammonium chloride, and the amount of the mineralizer added is 0.5% to 5% of the total mass of the raw materials.

[0006] 3) Put the powder prepared in step 2) into a tube furnace, heat it to 900~1100℃ at a rate of 5~10℃ / min in a reducing atmosphere, sinter it for 1.5~3h, then slowly cool it to room temperature at a rate of 5~10℃ / min, take it out and grind it evenly to obtain a red fluorescent pigment. The reducing atmosphere is a mixture of 5~10% H2 and 95~90% N2 / Ar.

[0007] Synthesis mechanism of the present invention: Eu 2+ The introduction of ions will change the energy band structure of the matrix material, thus affecting its ability to absorb light. 2+ As the concentration increases, the fluorescent pigment can absorb more light energy, thus showing a change in body color. In addition, the role of mineralizers is as follows: (1) Promote liquid phase formation and solid phase reaction: Mineralizers can promote the formation of a small amount of liquid phase at a lower temperature, which helps to accelerate the solid phase reaction; at the same time, it can also improve the color rendering properties of the pigment, including making the color more vivid and enhancing the tinting strength; (2) Activating crystal lattices and accelerating crystal growth: Mineralizers can form solid solutions (substitutional or interstitial) or intermediate compounds with reactants, thereby activating the crystal lattices of reactants. This activation helps accelerate the growth process of crystals and improve the quality and performance of crystals.

[0008] Compared with the prior art, the present invention has the following advantages: (1) The high temperature resistant red inorganic fluorescent pigment for ceramics of the present invention has bright color and adjustable chromaticity; (2) The high temperature resistant red inorganic fluorescent pigment for ceramics of the present invention has a stable structure, high crystallinity and no impurities; (3) The high temperature resistant red inorganic fluorescent pigment for ceramics of the present invention has excellent high temperature stability; (4) The high temperature resistant red inorganic fluorescent pigment for ceramics of the present invention has a high luminous intensity; (5) The preparation process of the high temperature resistant red inorganic fluorescent pigment for ceramics of the present invention is simple and has low requirements on equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 The XRD diagrams of the red fluorescent pigments prepared in Examples 1 and 2 of the present invention.

[0010] Figure 2 Reflection & emission spectra of the red fluorescent pigment prepared in Examples 1 and 2 of the present invention.

[0011] Figure 3 The Lab value variation curve of the red fluorescent pigment prepared in Example 1 of the present invention after sintering at different temperatures for 1 hour.

[0012] Figure 4 The Lab value variation curve of the red fluorescent pigment prepared in Example 2 of the present invention after sintering at different temperatures for 1 hour. DETAILED DESCRIPTION

[0013] The present invention is further explained below with reference to specific embodiments.

[0014] Example 1 Calcium-based red fluorescent pigment (CaS:Eu 2+ ) CaCO3 (1.3522g), S powder (1.7330g), Eu2O3 (0.0240g) and NH4Cl (0.0311g) were weighed on an electronic balance, with a mass tolerance of ±0.0005g. The weighed raw materials were poured into an agate mortar, manually ground for 20 minutes, placed in a corundum crucible and placed in a tube furnace, heated to 1000°C at a heating rate of 5°C / min in a reducing atmosphere, and kept at 1000°C for 2 hours. After the insulation was completed, the samples were cooled to room temperature at a cooling rate of 5°C / min, and finally the samples were taken out and ground to obtain a stable red inorganic fluorescent pigment.

[0015] Example 2 Strontium-based red fluorescent pigment (SrS:Eu 2+ ) Use an electronic balance to weigh SrCO3 (1.2146g), S powder (1.0551g), Eu2O3 (0.0146g) and NH4Cl (0.0228g) respectively. The allowable error of mass is ±0.0005g. The preparation method is the same as that in Example 1.

[0016] The chromaticity values ​​of the red fluorescent pigments prepared in the above Examples 1 and 2 are shown in Tables 1 and 2 below: Table 1 Chromaticity values ​​of calcium-based red fluorescent pigments Table 2 Chromaticity values ​​of strontium-based red fluorescent pigments From the Lab values ​​of samples No. 1 and 2 in Table 1, it can be found that when the europium ion doping concentration is high, the redness value (a*) of the fluorescent pigment sample can be significantly improved. From the samples No. 2-6, it can be found that when different mineralizers are used, the Lab values ​​of the samples have changed significantly. Among them, the lightness value (L*) of the synthetic sample is significantly improved when NH4F is used as the mineralizer; the redness value (a*) is significantly improved when K2CO3 is used as the mineralizer.

[0017] From the Lab values ​​of samples No. 1 and 2 in Table 2, it can be found that when the europium ion doping concentration is high, the redness value (a*) of the fluorescent pigment sample can be significantly improved. From the samples No. 2-6, it can be found that when different mineralizers are used, the Lab values ​​of the samples have changed significantly. Among them, the lightness value (L*) of the synthetic sample is significantly improved when NH4F is used as the mineralizer; the lightness value (L*) and redness value (a*) are significantly improved when NH4Cl is used as the mineralizer.

[0018] In addition, by Figure 1 It can be seen that the characteristic peaks of the fluorescent pigment samples prepared in Examples 1 and 2 of the present invention are consistent with the characteristic peaks on the CaS and SrS standard cards, respectively, indicating that pure phase CaS:Eu was successfully synthesized. 2+ and SrS:Eu 2+ Red fluorescent pigment.

[0019] Secondly, from Figure 2 It can be seen that CaS:Eu 2+ and SrS:Eu 2+ Red fluorescent pigments have strong reflection peaks at wavelengths of 450-780nm. As can be seen from the emission spectrum on the right, under 450nm excitation, CaS:Eu 2+ The emission spectrum peak is located at 660nm, SrS:Eu 2+ The emission spectrum peak is located at 620nm.

[0020] Furthermore, Figure 3 , Figure 4 The Lab value variation curves of Example 1 and Example 2 after sintering in air from 500°C to 800°C at intervals of 50°C for 1 hour.

[0021] Depend on Figure 3 It can be observed that, compared with the sample that has not been sintered in air (25°C), the L value does not change significantly before the temperature reaches 650°C, increases slightly between 650°C and 750°C, and increases significantly above 750°C; the a value does not change significantly before 750°C, and decreases significantly above 750°C; the b value does not change significantly.

[0022] Depend on Figure 4It can be observed that, compared with the sample that has not been sintered in air (25°C), the L value does not change significantly below 750°C, but increases significantly above 750°C; the a value and b value fluctuate only slightly.

[0023] This shows that the CaS:Eu synthesized in Example 1 2+ and the SrS:Eu synthesized in Example 2 2+ They all have excellent high-temperature stability, which provides strong support for their application as ceramic fluorescent pigments.

Claims

1. A high temperature resistant red fluorescent pigment for ceramics, characterized in that: The main component of the red pigment is (M 1-x Eu x )S, where M=Sr, Ca, or Sr+Ca, 0<x≤0.

05.

2. A method for preparing the high temperature resistant red fluorescent pigment for ceramics as claimed in claim 1, characterized in that: The following steps are involved: 1) Using M compound, S powder and europium compound as raw materials, weigh the raw materials respectively according to the stoichiometric ratio of each element in the above chemical formula, wherein the molar ratio of M compound to S powder is 1:2-1:6; 2) Put the weighed raw materials into an agate mortar, add mineralizer and grind and mix evenly; 3) Place the powder prepared in step 2) into a tubular furnace, heat to 900-1100°C at a rate of 5-10°C / min in a reducing atmosphere, sinter for 1.5-3h, then slowly cool to room temperature at a rate of 5-10°C / min, take out and grind evenly to obtain a red fluorescent pigment.

3. The method for preparing the high temperature resistant red fluorescent pigment for ceramics as claimed in claim 2, characterized in that: In step 1), the M compound is one or more of a carbonate containing M, an oxide containing M or a nitrate containing M.

4. The method for preparing the high temperature resistant red fluorescent pigment for ceramics as claimed in claim 2, characterized in that: In step 1), the europium compound is one or more of europium oxide, europium carbonate or europium nitrate.

5. The method for preparing the high temperature resistant red fluorescent pigment for ceramics as claimed in claim 2, characterized in that: In step 2), the mineralizer is one or more of ammonium fluoride, potassium carbonate, sodium carbonate, lithium carbonate or ammonium chloride, and the amount of the mineralizer added is 0.5% to 5% of the total mass of the raw materials.

6. The method for preparing the high temperature resistant red fluorescent pigment for ceramics as claimed in claim 2, characterized in that: In step 3), the reducing atmosphere is a mixture of 5-10% H2 and 95-90% N2 / Ar.

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