JP6912770B2 - Ceramic body with thermochromic properties and its manufacturing method - Google Patents

Description

The present invention relates to a ceramic body having thermochromic properties (also referred to as a ceramic thermochromic body) and a method for producing the same.

The change in color due to thermal energy is called a thermochromic phenomenon, and since the temperature change can be intuitively felt from the visual color change, it has been studied in many fields. So far, most of the materials exhibiting the thermochromic phenomenon are organic materials, and it is almost impossible to use them at 100 ° C. or higher, and there are restrictions in high temperature durability and high temperature discoloration temperature range. Therefore, it is desired to develop a new material made of an inorganic material exhibiting a thermochromic phenomenon.

The thermochromic material made of an inorganic material is obtained by a production method for forming vanadium dioxide-containing particles by hydrothermally reacting a reaction solution containing a vanadium compound selected from _{V 2} O _{4 and its hydrate with water.} There is a material (Patent Document 1).
Further, it contains rutile-type (R-phase) vanadium dioxide (VO ₂ ) particles and rutile-type titanium dioxide (TiO ₂ ) particles, and at least one vanadium dioxide (VO ₂ ) particle is titanium dioxide (TIO 2). on the particles _2), larger than the particles of the titanium dioxide (TiO _2), thermochromic particles is known to be grown to the rod-like (Patent Document 2).

Japanese Unexamined Patent Publication No. 2016-191015 Japanese Unexamined Patent Publication No. 2010-031235

However, the above-mentioned material is mainly developed for automatic dimming applications such as window glass, and the evaluation temperature is 80 ° C. There is also the problem of toxicity of vanadium itself. It has been difficult to use a thermochromic material containing vanadium dioxide as a main component for heating ceramic products such as clay pots for home use and high-temperature piping applications in factories where the danger of heat can be visually detected. In particular, there is no known ceramic body having a thermochromic property that can withstand heating of 1000 ° C. or higher and has a property of reversibly changing color with a change in atmospheric temperature of about 25 ° C. to 500 ° C.

The present invention has been made to deal with such a problem, and has a property of withstanding heating of 1000 ° C. or higher and reversibly changing color with a change of atmospheric temperature of about 25 ° C. to 500 ° C. An object of the present invention is to provide a ceramic body having thermochromic properties and a method for producing the same.

The ceramic body of the present invention is _{composed of a fired product of a mixture of M 1-x} L _x TiO ₃ and a transition metal compound, and has a thermochromic property in which the color changes reversibly with a change in temperature.
In M _1-x L _x TiO ₃ , M is Ba, Sr, Ca, or Mg, L is a lanthanoid element, and x is 0 to 1.0.
Ceramic bodies of the present invention that the transition metal compound is contained 0.001 to 1.0 moles with respect to _{M 1-x L x TiO 3} 1 mole is characterized. Further, the transition metal compound is a compound of at least one element selected from Fe, Mn, Cu, Co, Cr and Ni.

_{The M 1-x} L _x TiO ₃ in the ceramic body of the present invention is characterized by being Ba _1-x L _x TiO ₃ . Further, the above L is La. Further, the transition metal compound is a compound of Cr element.

A temperature change band adjusting material is blended in a mixture of _{M 1-x} L _x TiO ₃ and a transition metal compound in an amount of 0.01 to 0.5 mol with respect to 1 mol of the _{above M 1-x} L _x TiO _3. It is characterized by.

In the method for producing a ceramic body of the present invention, after TiO ₂ , the compound of M, and the compound of L are mixed, this mixture is fired in air at 900 to 1400 ° C. to obtain a base material powder. It is provided with a step of producing, a step of mixing the transition metal compound with the base metal powder, and a step of firing a mixture of the transition metal compound mixed with the base metal powder in air at 1000 to 1500 ° C. It is characterized by.

In another method for producing the ceramic body of the present invention, _{a step of mixing TiO 2} , the compound of M, the compound of L, and the transition metal compound is mixed, and the mixed mixture is mixed in air. It is characterized by including a step of firing at 1000 to 1500 ° C.

Since the ceramic body of the present invention _{is a fired product of a mixture of M 1-x} L _x TiO ₃ and a transition metal compound, it can withstand heating of 1000 ° C. or higher and changes in temperature in the temperature range of 25 ° C. to 500 ° C. The color changes reversibly with this. When the temperature changes from low temperature to high temperature, it changes from greenish to reddish brown, which is close to human senses and easy to detect danger.

It is a figure which shows the thermochromic property of barium titanate (BaTIO _3). It is a figure which shows the thermochromic property of barium titanate to which a transition metal was added. It is a figure which shows the thermochromic property of the sample which added Fe to the base material which replaced a part of barium with lantern. It is a figure which shows the thermochromic property of the ceramic body which added the transition metal to the strontium titanate base material. It is a figure which shows the thermochromic property of the ceramic body which added the transition metal to the strontium titanate base material which partially replaced a part of strontium with lantern. It is a figure which shows the thermochromic property when 0.001 mol of the transition metal was added to Ba _0.9 La _0.1 TiO _{3 base material.} It is a figure which shows the thermochromic property when 0.1 mol of the transition metal is added to Ba _0.9 La _0.1 TiO _{3 base material.} It is a figure which shows the thermochromic property when Cr is added to Ba _0.9 La _0.1 TiO _{3 base material.} It is a figure which shows the Cr density dependence of the color difference ΔE shown in FIG. It is a figure which shows the thermochromic property when SiO _{2 is added.} It is a figure which shows the thermochromic property when Al ₂ O _{3 is added.} It is a figure which shows the result of having measured the thermochromic property of a glaze layer.

_{A ceramic body based on metal titanate (MTIO 3} ), which is a perovskite-based composite oxide known as a ferroelectric substance, exhibits thermochromic properties in which the color changes reversibly with changes in temperature. I found. In particular, it has been found that it withstands heating of 1000 ° C. or higher and exhibits thermochromic properties in a temperature range of 25 ° C. to 500 ° C. The present invention is based on such findings.

For thermochromic properties, the color change due to temperature was quantified by calculating ^{CIE-L *} a ^* b ^{* (JIS Z 8781).} The thermochromic property is measured by measuring the Yxy value using a CR-300 color difference meter manufactured by Minolta Co., Ltd., and converting it to a more general color system, CIE-L ^* a ^* b ^* color system. did. The conversion formula and the calculation formula of the color difference ΔE are shown in Equation 1.

In the L ^* a ^* b ^* color system, L ^* represents brightness, L ^* = 0 represents black, and L ^* = 100 represents white. a ^* and b ^* indicate the color direction, + a ^* indicates the red direction, -a ^* indicates the green direction, + b ^* indicates the yellow direction, and -b ^* indicates the blue direction. In addition, the color becomes brighter as the absolute value of each value increases, and becomes dull as the absolute value decreases.

The way the human eye perceives due to the color difference ΔE is as follows.
0 to 0.1: Color difference cannot be visually identified 0.2 to 0.4: Limit that a person accustomed to color inspection can identify color difference 0.4 to 0.8: Strict color difference, in the butt part Range of use 0.8 to 1.5: Range of common use in product color management 1.2 to 3.0: Range of tolerance for distant areas and high-saturation colors 3.0 to: Range of different colors Range that often becomes a complaint 12.0 ~: Another color system

A sample for measuring the thermochromic property of the ceramic body was prepared by the following method. TiO ₂ and a compound of metal M, for example, a carbonate of metal M, are mixed. When a part of the metal M is replaced with a lanthanoid element, it is mixed at the same time as the compound of the metal M. For mixing, for example, using an alumina ball mill, 200% by mass of water is added to the solid content, and wet mixing is performed for about 4 hours. After drying at 100 ° C., it is further crushed using a mortar. The mixed powder is calcined at 1200 ° C. for 1 hour to prepare a base material powder. The base metal powder alone or transition metals described later are further added to the base material powder, press-molded, and then fired at 1100 ° C., 1200 ° C. or 1300 ° C. to obtain sintered pellets.
Further, as another production method, _{a compound of TiO 2} and metal M, for example, a carbonate of metal M and a transition metal compound are mixed. When a part of the metal M is replaced with a lanthanoid element, it is mixed at the same time as the compound of the metal M. For mixing, for example, using an alumina ball mill, 200% by mass of water is added to the solid content, and wet mixing is performed for about 4 hours. After drying at 100 ° C., it is further crushed using a mortar. The mixed powder is calcined at 1200 ° C. for 1 hour to prepare a base material powder. This base metal powder alone is press-molded and then fired at 1100 ° C., 1200 ° C. or 1300 ° C. to obtain sintered pellets.
Using the sintered pellets thus produced, the thermochromic property was measured in the range of 25 to 500 ° C.

FIG. 1 shows the results of measuring the thermochromic properties of _{barium titanate (BaTIO 3} ), which is a perovskite-based composite oxide known as a ferroelectric substance. Barium titanate alone exhibits thermochromic properties, but the degree of color development is low.
Next, the thermochromic property of barium titanate to which 0.001 mol of a transition metal was added as a colorant was measured. Fe, Mn, Cu, Co, Cr and Ni were used as the transition metals. The results are shown in FIG. In FIG. 2, as the measurement temperature became higher, the color changed in the direction in which the absolute values of the a-axis and the b-axis increased. The color measurement temperatures are 25 ° C, 100 ° C, 200 ° C, and 300 ° C.
As a result of the measurement, the barium titanate to which the transition metal was added showed a different color change depending on the type of the transition metal added, as compared with the barium titanate alone. That is, the thermochromic property of barium titanate was improved by adding 0.001 mol of transition metals.

Examples of the transition metal include Sc of the 21st element of the periodic table to Cu of the 29th element, Y of the 39th element to Ag of the 47th element, and Hf of the 72nd element to Au of the 79th element. In the present invention, the above Fe, Mn, Cu, Co, Cr and Ni are preferable.

Next, for the purpose of improving the thermochromic property, the thermochromic property of a sample in which 0.01 mol of Fe was added to a base material in which a part of barium of barium titanate was replaced with lantern was measured. The results are shown in FIG. FIG. 3A shows the amount of La added and the change in color with a on the horizontal axis and b on the vertical axis, and FIG. 3B shows the temperature dependence of the color difference ΔE in FIG. 3 (a). c) is a diagram showing the La amount dependence of the color difference ΔE at 300 ° C.
As shown in FIG. 3A, the thermochromic property was improved by substituting a part of barium of barium titanate with lantern. Since the thermochromic property is also shown by barium titanate alone (see FIG. 1), the thermochromic property is shown at x = 0 to 1.0 in consideration of FIGS. 3 (b) and 3 (c). The substitution amount of the lanthanum exhibiting thermochromic property is x = 0.002 to 1.0, preferably x is 0.002 or more and less than 1.0, and more preferably 0.005 to 0.5 mol. rice field.

Strontium titanate was used instead of barium barium titanate to measure thermochromic properties. The results are shown in FIGS. 4 and 5. FIG. 4 shows the results of a ceramic body in which 0.1 mol of Ni, Fe, and Cr were added as transition metals to the base material of strontium titanate alone, and FIG. 5 shows a part of strontium in strontium titanate (x = 0. This is the result of a ceramic body in which 0.1 mol of Ni, Fe, and Cr were added as transition metals to the base metal in which 1) was replaced with lanthanum.
In FIGS. 4 and 5, (a) and (b) are diagrams in which the firing temperature at the time of sample preparation is 1200 ° C., (c) and (d) are diagrams in which the firing temperature is 1300 ° C., and (a) and (d) are shown. c) is a diagram showing transition metal addition and color change with a on the horizontal axis and b on the vertical axis, and (b) and (d) show the temperature dependence of the color difference ΔE, respectively.

As shown in FIG. 4, the thermochromic property was exhibited by adding a transition metal to strontium titanate alone. That is, even if M in M _1-x L _x TiO ₃ was strontium, it showed thermochromic properties similar to barium of barium titanate. It is considered that this is because both form a perovskite-based composite oxide.

As shown in FIG. 5, by adding a transition metal to the base material in which a part (x = 0.1) of strontium in strontium titanate was replaced with lantern, higher thermochromic properties than strontium titanate were exhibited. .. That is, it showed thermochromic properties similar to barium titanate.

From the above experimental results, M _{and L in M 1-x} L _x TiO ₃ can be used as long as they are the types and amounts of elements capable of forming a perovskite-based composite oxide.
M is preferably a divalent metal, specifically Ba, Sr, Ca, or Mg. Among these, Ba and Sr are preferable, and Ba is particularly preferable because the dielectric constant is large and the thermochromic property is high.

L is a lanthanoid element and represents La of atomic number 57 to Lu of 71. The lanthanoid element forms a perovskite-based composite oxide in which a part of M _{in MTIO 3 is substituted.} In the present invention, La is preferable because it can be easily converted into a semiconductor by substitution and exhibits high thermochromic properties.

Using Ba _0.9 La _0.1 TiO ₃ as a base material, the thermochromic property due to the addition of transition metals was investigated. The results are shown in FIGS. 6 and 7. FIG. 6 is a diagram showing the change in color when 0.001 mol of Fe, Mn, Ni, Cu, Co, and Cr are added as transition metals, with a on the horizontal axis and b on the vertical axis. FIG. 6A shows the results when the transition metal was added and then calcined at 1200 ° C., and FIG. 6B shows the results when calcined at 1300 ° C.
FIG. 7 shows the results of a ceramic body in which 0.1 mol each of Ni, Fe, and Cr was added to the _{Ba 0.9} La _0.1 TiO _{3 base material.}
In FIG. 7, (a) and (b) are diagrams in which the firing temperature at the time of sample preparation is 1200 ° C., (c) and (d) are diagrams in which the firing temperature is 1300 ° C., and (a) and (c) are. It is the figure which showed the transition metal addition and the color change with a as the horizontal axis and b as the vertical axis, and (b) and (d) show the temperature dependence of the color difference ΔE, respectively.

As shown in FIGS. 7 (b) and 7 (d), the thermochromic property was improved by adding Ni, Fe, and Cr to the base metal among the transition metals, and particularly by adding Cr. Therefore, using Cr as a typical example, the _{amount added to the Ba 0.9} La _0.1 TiO ₃ base material was investigated in detail. The results are shown in FIGS. 8 and 9. FIG. 8 shows the results of a ceramic body in which 0.01 to 1.0 mol of Cr was added to 1.0 mol of _{Ba 0.9} La _0.1 TiO _{3 base material, and (a) and (b) had a firing temperature of 1200 ° C.} (C) and (d) are the results of the firing temperature of 1300 ° C. 9A and 9B are diagrams showing the Cr concentration dependence of the color difference ΔE based on the results of FIG. 8, where FIG. 9A is a result of a firing temperature of 1200 ° C. and FIG. 9B is a result of a firing temperature of 1300 ° C.

Results of FIGS. 7 _{9, M 1-x L x} TiO 3 to the base material the transition metal compound improves thermochromic properties by adding, the amount of _{addition, M 1-x L x TiO} 3 preform 1 It was found that the transition metal compound was 0.001 to 1.0 mol, preferably less than 0.03 to 0.50 mol, relative to the mole.

The thermochromic property was investigated by further adding a temperature change band adjusting material to the above ceramic body. The temperature change band adjusting material does not change color by itself, but is a material that adjusts the color change due to thermochromic properties. Examples of the temperature discoloration band adjusting material include SiO ₂ , Al ₂ O ₃ , ZrO ₂ , and ZrSiO ₄ .

In FIG. 10, 0.1 mol of Cr was added to 1.0 mol of _{Ba 0.9} La _0.1 TiO _{3 base material, and SiO 2} as a temperature change band adjusting material was added to 0.01 to 1.0 mol of the base material. It is the result of the ceramic body to which 1.0 mol was added, (a) and (b) are the result of the firing temperature of 1200 ° C., and (c) and (d) are the result of the firing temperature of 1300 ° C.
In FIG. 11, 0.1 mol of Cr was added to 1.0 mol of _{Ba 0.9} La _0.1 TiO _{3 base material, and Al 2} O ₃ as a temperature change band adjusting material was added to 1.0 mol of the base material. It is the result of the ceramic body to which 05 to 0.20 mol was added, (a) and (b) are the result of the firing temperature of 1200 degreeC, and (c) and (d) are the result of the firing temperature of 1300 degreeC.

As shown in FIGS. 10 and 11, the thermochromic property was further improved by adding the temperature change band adjusting material. It was also found that _{the desirable amount of SiO 2} added was 0.5 mol or less, and the desirable amount of Al ₂ O ₃ added was 0.5 mol or less.

Since the color of the ceramic body changes reversibly with a change in temperature, it is used alone or in combination with other materials as a powder, a molded product, a sintered body, a thin film body, or a glaze. be able to. Unlike the organic thermochromic body, this ceramic body is an inorganic thermochromic body that can reversibly change its color even at a high temperature of 200 ° C. or higher. Therefore, the ceramic body of the present invention is used for the surface of tableware and cooking utensils (glaze, etc.) to visualize the temperature (earthen pot, tempura pot, frying pan, etc.), and the outer wall of bricks, tiles, etc. of the firing furnace. It can be used for visualization of dangerous parts by applying the material to high temperature parts, and visualization of dangerous parts by applying to high temperature parts such as high temperature pipes in chemical factories.

In particular, _{the hue change of the ceramic body obtained by adding Cr to the Ba 0.9} La _0.1 TiO ₃ base material changes from green to reddish brown when the temperature changes from low temperature to high temperature, so that it is human sense. A synergistic effect can be expected with the fact that it is easy to detect danger in the near future.

Example 1
A glaze was prepared using a ceramic body obtained by adding 0.1 mol of Cr to 1 mol of _{Ba 0.9} La _0.1 TiO _{3 base material and firing at 1200 ° C.} This ceramic body was pulverized so as to have a particle size of 100 to 300 μm to obtain a ceramic powder. 23.1% by mass of this ceramic powder is mixed with the composition (95% by mass of frit for ceramics, 5% by mass of frog-eye clay) that is the base material of the glaze, and the glaze is made into a slurry-like glaze by making it an aqueous solution of about 60%. Was produced. This glaze was glazed on a fired body (ceramic base material) as a base, dried, and then fired at 900 ° C. to prepare a fired body having a glaze layer formed on the surface. The result of measuring the thermochromic property of this glaze layer is shown in FIG. FIG. 12 (a) shows the transition metal addition and the color change with a on the horizontal axis and b on the vertical axis, and FIG. 12 (b) shows the temperature dependence of the color difference ΔE.

Example 2
A fired body having a glaze layer formed on the surface was prepared in the same manner as in Example 1 except that 15.3% by mass of the ceramic powder used in Example 1 was added to the composition used as the base material of the glaze. .. The result of measuring the thermochromic property in the same manner as in Example 1 is shown in FIG.

Example 3
A fired body having a glaze layer formed on the surface was prepared in the same manner as in Example 1 except that the ceramic powder used in Example 1 was blended in an amount of 5.7% by mass in the composition used as the base material of the glaze. .. The result of measuring the thermochromic property in the same manner as in Example 1 is shown in FIG.

As shown in FIG. 12, all of Examples 1 to 3 showed thermochromic properties.

Since the ceramic body of the present invention changes its color reversibly in a high temperature range, it can be used for visualization of dangerous places by installation in a high temperature part or the like.

Claims (7)

It is a ceramic body having a thermochromic property, which is composed of a fired product of a mixture of _{M 1-x} L _x TiO _{3 and a transition metal compound, and whose color changes reversibly with a change in temperature.}
M is Ba, Sr, Ca, or Mg.
L is a lanthanoid element, x is 0 to 1.0, and
Ceramic body, characterized in that the transition metal compound is contained 0.001 to 1.0 mole with respect to the _{M 1-x L x TiO 3} 1 mol. The ceramic body according to claim 1, wherein the transition metal compound is a compound of at least one element selected from Fe, Mn, Cu, Co, Cr and Ni. The ceramic body according to claim 1 or 2, wherein M is Ba. The ceramic body according to any one of claims 1 to 3, wherein L is La. The ceramic body according to any one of claims 1 to 4, wherein the transition metal compound is a compound of Cr element. The method for producing a ceramic body according to claim 1.
A step _{of mixing TiO 2} , the compound of M, and the compound of L, and then firing this mixture in air at 900 to 1400 ° C. to produce a base metal powder.
The step of mixing the transition metal compound with the base metal powder and
A method for producing a ceramic body, which comprises a step of firing a mixture of the transition metal compound mixed with the base metal powder in air at 1000 to 1500 ° C. The method for producing a ceramic body according to claim 1.
A step of mixing TiO ₂ , the compound of M, the compound of L, and the transition metal compound,
A method for producing a ceramic body, which comprises a step of firing the mixed mixture in air at 1000 to 1500 ° C.

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