Ceramic composite

Abstract

To provide ceramics having both thermochromism and photochromism.SOLUTION: A ceramic composite has at least two oxide phases of a Y3Al5O12 phase and an Al2O3 phase as a lamellar structure and includes Hf of 0.1 at%. The ceramic composite heated from the room temperature to at least 200°C increases a reflection spectrum intensity at a wavelength of 625 nm or more and 780 nm or less and decreases a reflection spectrum intensity of 425 nm or more and 485 nm or less, and the ceramic composite irradiated with any light having a wavelength of 365 nm or more and 505 nm or less decreases a reflection spectrum intensity having a wavelength of 625 nm or more and 780 nm or less and increases a reflection spectrum intensity of 425 nm or more and 485 nm or less.SELECTED DRAWING: Figure 14

Description

Technical Field

[0001] The present invention relates to a ceramic composite.

Background Art

[0002] A phenomenon in which the color or optical properties of an article change due to a temperature change such as heating is called thermochromism, and the temperature change can be recognized from the color change by vision.

[0003] In addition, a phenomenon in which the color of an article changes due to light irradiation is called photochromism, and the presence or absence of light irradiation can be recognized from the color change by vision.

[0004] Examples of materials having thermochromism include a ceramic body shown in Patent Document 1. The ceramic body of Patent Document 1 is composed of a fired product of a mixture of M 1-x L x TiO3 and a transition metal compound. M is Ba, Sr, Ca, Mg, L is a lanthanoid element, and x is 0 to 1.0. The transition metal compound is a compound of at least one element selected from Fe, Mn, Cu, Co, Cr, and Ni, and the transition metal compound is M 1-x L x is contained in an amount of 0.001 to 1.0 mol with respect to 1 mol of TiO3.

[0005] Examples of materials having photochromism include a ceramic material shown in Patent Document 2. Patent Document 2 shows a photochromic paint containing polysilazane and silver halide. After applying this photochromic paint to a substrate, the paint is ceramized to obtain a photochromic material.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, there was no ceramic that had both thermochromism and photochromism and could detect both temperature changes and the presence or absence of light irradiation. Therefore, in order to detect both temperature changes and the presence or absence of light irradiation, two different materials with thermochromism and photochromism respectively had to be mounted on one detection device, which hindered the miniaturization of the device.

[0008] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a ceramic having both thermochromism and photochromism.

Means for Solving the Problems

[0009] In order to solve the above problems, the present invention provides a ceramic composite as the ceramic. The ceramic composite of the present invention has at least two oxide phases of Y3Al5O 12 phase and Al2O3 phase in a lamellar structure, contains 0.1 at% of Hf, and when heated from room temperature to at least 200 ° C, the intensity of the reflection spectrum at a wavelength of 625 nm or more and 780 nm or less increases, and the intensity of the reflection spectrum at 425 nm or more and 485 nm or less decreases. Next, when irradiated with light having any wavelength of 365 nm or more and 505 nm or less, the intensity of the reflection spectrum at a wavelength of 625 nm or more and 780 nm or less decreases, and the intensity of the reflection spectrum at 425 nm or more and 485 nm or less increases.

Effects of the Invention

[0010] According to the ceramic composite of the present invention, it is possible to have both thermochromism and photochromism.

Brief Description of the Drawings

[0011]

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Figure 17

Mode for Carrying Out the Invention

[0012] The first feature of this embodiment is that it has at least two oxide phases, namely the Y3Al5O 12 phase and the Al2O3 phase, in a lamellar structure, contains 0.1 at% of Hf, and when heated from room temperature to at least 200 °C, the reflection spectrum intensity at wavelengths of 625 nm or more and 780 nm or less increases, while the reflection spectrum intensity at 425 nm or more and 485 nm or less decreases. Next, when irradiated with light having any wavelength in the range of 365 nm or more and 505 nm or less, the reflection spectrum intensity at wavelengths of 625 nm or more and 780 nm or less decreases, while the reflection spectrum intensity at 425 nm or more and 485 nm or less increases. This is what is meant by a ceramic composite.

[0013] The second feature is that the wavelength of the light is any one of 365 nm, 375 nm, 405 nm, 450 nm, and 505 nm.

[0014] According to these configurations, the ceramic composite according to the present invention can have both thermochromism and photochromism.

[0015] In the present invention, room temperature refers to a state where neither heating nor cooling is applied from the outside, and it refers to a temperature range of 1°C to 30°C.

[0016] Hereinafter, embodiments of the present invention will be described in detail with appropriate reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. In this embodiment, a ceramic composite will be described as the ceramics.

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. FIGS. 1 to 8 are diagrams for explaining a plurality of ceramic composites and a method for manufacturing the same according to an embodiment of the present invention.

[0018] As shown in FIG. 1, a manufacturing apparatus 1 for a ceramic composite includes a growth container 3 for growing the ceramic composite 2 and a lifting container 4 for lifting the grown ceramic composite 2, and grows the ceramic composite 2 by the EFG (Edge-defined Film-fed Growth) method.

[0019] The growth container 3 includes a crucible 5, a crucible drive unit 6, a heater 7, an electrode 8, a die 9, and a heat insulating material 10. The crucible 5 is made of molybdenum or tungsten and melts the raw material. The crucible drive unit 6 rotates the crucible 5 about its vertical axis. The heater 7 heats the crucible 5. Also, the electrode 8 energizes the heater 7. The die 9 is installed in the crucible 5 and determines the liquid surface shape of the raw material melt (hereinafter, simply referred to as "melt" as necessary) 21 when the ceramic composite 2 is lifted. The heat insulating material 10 surrounds the crucible 5, the heater 7, and the die 9.

[0020] Furthermore, the growth container 3 is provided with an atmosphere gas inlet 11 and an exhaust port 12. The atmosphere gas inlet 11 is an inlet for introducing, for example, argon gas as the atmosphere gas into the growth container 3, and prevents oxidation and consumption of the crucible 5, the heater 7, and the die 9. On the other hand, the exhaust port 12 is provided for exhausting the inside of the growth container 3.

[0021] The lifting container 4 includes a shaft 13, a shaft drive unit 14, a gate valve 15, and a substrate entrance / exit 16, and lifts a plurality of flat ceramic composites 2 grown from the seed crystal 17. The shaft 13 holds the seed crystal 17. The shaft drive unit 14 raises and lowers the shaft 13 toward the crucible 5 and rotates the shaft 13 about its lifting direction as an axis. The gate valve 15 separates the growth container 3 and the lifting container 4. The substrate entrance / exit 16 is for inserting and removing the seed crystal 17.

[0022] The manufacturing apparatus 1 also has a control unit (not shown), and this control unit controls the rotation of the crucible drive unit 6 and the shaft drive unit 14.

[0023] Next, the die 9 will be described. The die 9 is made of molybdenum and has a number of partition plates 18 as shown in FIG. 2. In FIG. 2, as an example of the die, it shows a case where there are 30 partition plates 18 and 15 dies 9 are formed. The partition plates 18 have the same flat shape and are arranged parallel to each other so as to form minute gaps (slits) 19, forming one die 9. The slit 19 is provided across substantially the entire width of the die 9. Also, the plurality of dies 9 have the same shape and are arranged in parallel at a predetermined interval so that their longitudinal directions are parallel to each other, so that a plurality of slits 19 are provided. An inclined surface 30 is formed at the upper part of each partition plate 18, and by arranging the inclined surfaces 30 facing each other, an acute-angle opening 20 is formed. The slit 19 has the role of raising the melt 21 from the lower end of each die 9 to the opening 20 by capillary action. The symbol t in FIGS. 2 and 3 indicates the thickness of the die 9. The symbol D in FIG. 2 indicates the gap between the dies 9. The symbol T in FIG. 3 indicates the thickness of the seed crystal 17.

[0024] The raw material charged into the crucible 5 is melted (raw material melt) based on the temperature rise of the crucible 5 and becomes the melt 21. A part of this melt 21 enters the slit 19 of the die 9, rises in the slit 19 based on the capillary phenomenon as described above, and is exposed from the opening 20, and a raw material melt pool 22 is formed at the opening 20 (see Fig. 5(a)). In the EFG method, the ceramic composite 2 grows according to the shape of the melt surface formed in the raw material melt pool (hereinafter, referred to as "melt pool" as necessary) 22. In the die 9 shown in Fig. 2, since the shape of the melt surface is an elongated rectangle, a flat-plate-shaped ceramic composite 2 is manufactured.

[0025] Next, the seed crystal 17 will be described. As shown in Figs. 1, 4, and 5, in this embodiment, a substrate made of a flat-plate-shaped ceramic composite is used as the seed crystal 17. Further, the seed crystal 17 is arranged such that the plane direction of the seed crystal 17 and the longitudinal direction of the die 9 are orthogonal to each other at an angle of 90°. Also, since the seed crystal 17 and the ceramic composite 2 are also orthogonal to each other at an angle of 90°, the side surface of the ceramic composite 2 is shown in Fig. 1. Note that the reference numeral 28 in Figs. 3 and 4 is the crystal plane of the seed crystal 17.

[0026] If the contact area between the seed crystal 17 and the substrate holder (not shown) at the lower part of the shaft 13 is large, the seed crystal 17 will be deformed due to the stress caused by the difference in thermal expansion coefficient and may be damaged in some cases. On the contrary, the fixing of the seed crystal 17 may be loosened due to the difference in thermal expansion coefficient. Therefore, it is preferable that the contact area between the seed crystal 17 and the substrate holder is small. Also, the seed crystal 17 needs to have a substrate shape that can be securely fixed to the substrate holder.

[0027] Fig. 3 is a view showing an example of the substrate shape of the seed crystal 17. Among them, Figs. (a) and (b) of the same figure are those in which a notch 23 is provided at the upper part of the seed crystal 17. By using this notch 23, for example, a U-shaped substrate holder can be inserted from below the two notches 23, and it becomes possible to securely hold the seed crystal 17 while reducing the contact area.

[0028] Also, as shown in FIG. 3(c), a notch hole 24 may be provided inside the seed crystal 17. By using this notch hole 24, for example, locking claws can be inserted into two notch holes 24, so that while reducing the contact area between the substrate holder and the seed crystal 17, it becomes possible to securely hold the seed crystal 17.

[0029] Next, a method for manufacturing the ceramic composite 2 using the manufacturing apparatus 1 will be described. First, a predetermined amount of granulated raw material powder (as an example, a powder containing 63.44 wt% aluminum oxide, 36.23 wt% yttrium oxide, and 0.33 wt% hafnium oxide), which is the raw material of the ceramic composite, is put into and filled in the crucible 5 in which the die 9 is housed. The raw material powder may contain compounds and elements other than the above according to the purity or composition of the ceramic composite to be manufactured.

[0030] Subsequently, in order not to oxidize and consume the crucible 5, the heater 7, or the die 9, the inside of the growth container 3 is replaced with argon gas to make the oxygen concentration equal to or lower than a predetermined value.

[0031] Next, the crucible 5 is heated by the heater 7 to a predetermined temperature to melt the raw material powder. Since the melting point of aluminum oxide is about 2050°C to 2072°C, the heating temperature of the crucible 5 is set to a temperature equal to or higher than the melting point (for example, 2100°C). After heating for a while, the raw material powder melts to prepare a melt 21 of the raw material. Further, a part of the melt 21 rises through the slit 19 of the die 9 by capillary action and reaches the surface of the die 9, and a melt pool 22 is formed above the slit 19.

[0032] Next, as shown in FIGS. 4 and 5, while holding the seed crystal 17 at an angle perpendicular to the longitudinal direction of the melt pool 22 above the slit 19, the seed crystal 17 is lowered and brought into contact with the melt surface of the melt pool 22. The seed crystal 17 is previously introduced into the lifting container 4 from the substrate entrance / exit 16. In FIG. 4, for the sake of easy viewing of the slit 19 and the opening 20, the illustration of the melt 21 and the melt pool 22 is omitted.

[0033] FIG. 4 is a diagram showing the positional relationship between the seed crystal 17 and the partition plate 18. As described above, by making the plane direction of the seed crystal 17 orthogonal to the longitudinal direction of the partition plate 18, it becomes possible to reduce the contact area between the seed crystal 17 and the melt 21. Therefore, the contact portion of the seed crystal 17 conforms to the melt 21, and crystal defects are less likely to occur in the ceramic composite body 2 that is grown and developed.

[0034] When the seed crystal 17 is brought into contact with the melt surface, the lower part of the seed crystal 17 may be brought into contact with the upper part of the partition plate 18 and melted. FIG. 5(b) is a diagram showing a state where a part of the seed crystal 17 is melted. By melting a part of the seed crystal 17 in this way, the temperature difference between the seed crystal 17 and the melt 21 can be quickly eliminated, and the generation of crystal defects in the ceramic composite body 2 can be further reduced.

[0035] Subsequently, the substrate holder is pulled up at a desired rising speed, and the pulling up of the seed crystal 17 is started. Specifically, the substrate holder is raised at a desired speed by the shaft 13.

[0036] In addition, in order to make it easier to align the seed crystal with the opening 20 of the die 9, unevenness may be provided on the lower side of the seed crystal 17. FIG. 6 is a diagram illustrating the shape of the lower side of the seed crystal 17. FIG. 6(a) shows the case where the lower side has a comb-tooth shape, and FIG. 6(b) shows the case where the lower side has a saw-tooth shape.

[0037] The interval of this unevenness is adjusted according to the interval of the opening 20, and the convex portion is aligned with the center of the melt pool 22. By providing the convex portion, the convex portion can be used as the growth starting point of the ceramic composite body 2, and the ceramic composite body 2 can be formed more easily. Note that the shape of the unevenness is not limited to that shown in FIG. 6, and for example, a corrugated unevenness shape may be used.

[0038] Raise the substrate holder at a desired speed and grow the ceramic composite 2 along the longitudinal direction of the die 9 centering on the seed crystal 17 so as to widen it as shown in Fig. 7 (spreading). When the ceramic composite 2 spreads to the full width of the die 9 (the ends of the partition plates 18) (full spread), a flat-plate-shaped ceramic composite 2 having a width comparable to the full width of the die 9 and a large area is grown (straight-barrel process). Fig. 7 is a schematic diagram showing the state in which the width of the ceramic composite 2 widens in the spreading process. By obtaining a wide ceramic composite 2, the yield of the ceramic composite product is improved.

[0039] After growing the ceramic composite 2 to the full width of the die 9 by the spreading process, as shown in Fig. 8, perform a lifting process of lifting a flat-plate-shaped straight-barrel portion 26 having a constant width comparable to the full width of the die 9 to a desired length (straight-barrel length) at a desired speed (about 100 mm / hour) to obtain a flat-plate-shaped ceramic composite 2.

[0040] During the lifting process, perform temperature control using a heater 7 or the like so that the interface temperature of the melt 21 in the melt pool 22 formed above the slit 19 becomes constant. The ceramic composite 2 grows by being cooled while the melt 21 that has risen to the melt pool 22 comes into contact with the seed crystal 17, the neck 25, and the straight-barrel portion 26 and is lifted. Therefore, by controlling the temperature of the melt pool 22 to be constant, the crystal growth conditions can be kept equivalent during the growth period of the ceramic composite 2, and a uniform lamellar structure can be formed over the entire area of the ceramic composite 2.

[0041] Thereafter, allow the obtained ceramic composite 2 to cool naturally, open the gate valve 15, move it to the side of the lifting container 4, and take it out from the substrate inlet / outlet 16. Fig. 8 shows the appearance of the obtained flat-plate-shaped ceramic composite 2. The straight-barrel length is not particularly limited, but is preferably 2 inches or more (50.8 mm or more).

[0042] Also, as shown in FIG. 10, the entire width of the die 9 and the width of the seed crystal 17 may be made the same, and the ceramic composite 2 may be grown with the same width as the entire width of the seed crystal 17. In FIG. 10, in order to prioritize the visibility of the slit 19, the illustration of the melt 21 and the melt reservoir 22 is omitted.

[0043] By using the manufacturing apparatus 1, the seed crystal 17, and the die 9 as described above, a plurality of ceramic composites 2 can be simultaneously manufactured from a common seed crystal 17. Therefore, it is possible to reduce the manufacturing cost of the ceramic composite 2 per sheet.

[0044] Also, in the EFG method, a plurality of ceramic composites 2 are grown. Therefore, by uniformly cooling and annealing the plurality of ceramic composites 2, a uniform lamellar structure without variations can be obtained.

[0045] Therefore, the die 9 including the seed crystal 17 and the partition plate 18 needs to be precisely positioned. Thus, as shown in FIG. 1, the manufacturing apparatus 1 is provided with a crucible driving unit 6 that rotates the crucible 5 on which the die 9 is installed, and a control unit (not shown) that controls the rotation thereof. Also, regarding the shaft 13, a shaft driving unit 14 that rotates the shaft 13 and a control unit (not shown) that controls the rotation thereof are provided. That is, the positioning of the seed crystal 17 with respect to the die 9 is adjusted by rotating the shaft 13 or the crucible 5 by the control unit. Note that precise positioning of the seed crystal 17 and the die 9 can also be performed by using a die 9 in which a part of the inclined surface 30 of each partition plate 18 is cut out.

[0046] FIG. 9 is a micrograph showing the surface of the ceramic composite 2 obtained by the above-described EFG method. The range shown in the photograph in FIG. 9 is a square with a side length of 129 μm. As shown in FIG. 9, the ceramic composite 2 of the present invention is the first phase Y3Al5O 12A first phase and a second phase, the Al2O3 phase, exist as a eutectic, and the first phase and the second phase have a lamellar structure in which they are three-dimensionally intertwined with each other. In the present invention, by adding 0.33% by weight of hafnium oxide to the raw materials, the oxide phase of the produced ceramic composite 2 contains HfO2 as a metal oxide, and the content is 0.005 at% or more and 0.5 at% or less in terms of Hf. In FIG. 9, the region shown in dark color is the Y3Al5O 12 phase, and the region shown in light color is the Al2O3 phase. Further, there are few cases where the first phase and the second phase are separated independently in an island shape, and they have a region continuous in the three-dimensional direction.

[0047] Also, the composition ratio of the Y3Al5O 12 phase contained in the ceramic composite 2 is 19.72 ± 2.00 mol% near the eutectic composition. When the composition ratio of the Y3Al5O 12 phase is outside this range, it is difficult to uniformly form a lamellar structure by eutectic with the Al2O3 phase.

[0048] Further, since the ceramic composite 2 is manufactured using the EFG method as described above, a trace amount of molybdenum (Mo) or tungsten (W), which is the material of the crucible 5, dissolves into the melt 21 and is incorporated into the ceramic composite 2. Therefore, in addition to the above Y3Al5O 12 phase, Al2O3 phase, and HfO2, a trace amount of Mo or W is contained in the ceramic composite 2.

[0049] The amount of Mo or W contained in the ceramic composite 2 is preferably in the range of 1 mol·ppm or more and 30000 mol·ppm or less, and more preferably in the range of 100 mol·ppm or more and 3000 mol·ppm or less. In the production of the ceramic composite 2 using the EFG method, it is impossible to completely prevent the material of the crucible 5 from dissolving into the melt 21, and it is very difficult to make the content of Mo or W less than 1 mol·ppm. Also, when the content of Mo or W exceeds 30000 mol·ppm and becomes large, Y3Al5O 12It is not preferable because the crystallinity of the Y3Al5O12 phase and the Al2O3 phase deteriorates. When the content of Mo or W is set to 100 mol·ppm or more and 3000 mol·ppm or less, these problems are solved. Therefore, the content of Mo or W contained in the ceramic composite 2 is at least 1 mol·ppm or more and 30000 mol·ppm or less.

[0050] When a material other than Mo or W is used as the crucible 5, since the melting point is low, the amount of the crucible 5 material dissolved in the melt 21 increases, and the content of the elements derived from the crucible 5 contained in the ceramic composite 2 increases, which is not preferable. Also, using a material with a high melting point other than Mo or W as the material constituting the crucible 5 has problems such as reactivity with the melt 21 of the raw material and formability of the crucible 5, which is not preferable. Therefore, the ceramic composite 2 is manufactured using the EFG method, and Y3Al5O 12 In order to refine the lamellar structure of the Y3Al5O12 phase and the Al2O3 phase, it is important that Mo or W is contained in the ceramic composite 2 within the above range.

[0051] The shape and size of the ceramic composite 2 are not limited, but from the viewpoint of preventing deterioration of workability on the ceramic composite 2, a rectangular shape with a width of 0.5 mm or more and 300 mm or less and a length of 10 mm or more and 1000 mm or less, or a shape with a diameter of 0.5 mm or more and 2 mm or less is desirable. As described above, since the ceramic composite 2 of the present embodiment is manufactured using the EFG method, by increasing the width and the pulling-up length of the die 9, it is possible to easily obtain a large-area ceramic composite 2.

[0052] Also, the thickness of the ceramic composite 2 is not limited, but a range of 0.1 mm or more and 4.0 mm or less is preferable, and more preferably a range of 0.5 mm or more and 2.0 mm or less. When the thickness of the ceramic composite 2 is less than 0.1 mm, growth control becomes difficult in the EFG method, and the influence of the thickness due to manufacturing errors and the influence of thickness unevenness in the plane increase. Also, Y3Al5O contained in the ceramic composite 2 12Since the thermal conductivity of the phase is only about 1 / 4 of that of the Al2O3 phase, when the crystal is thickened, the heat dissipation deteriorates, and a temperature difference is likely to occur between the surface and the inside. Therefore, when the thickness of the ceramic composite 2 is greater than 4.0 mm, a temperature difference is likely to occur between the outside and the inside in the thickness direction during pulling up by the EFG method, colony structure is likely to occur, and the uniformity of the lamellar spacing is impaired, which is not preferable. Also, since the interface density between the Y3Al5O 12 phase and the Al2O3 phase becomes non-uniform, it is not preferable.

[0053] FIG. 11 is a photograph showing the appearance color of the ceramic composite according to the present embodiment at room temperature. FIG. 13 is a graph showing the reflection spectrum intensity of the ceramic composite according to the present embodiment under a light source (3000K). FIG. 14 is a graph showing the reflection spectrum intensity of the ceramic composite according to the present embodiment under a fluorescent lamp (visible light irradiation). FIG. 15 is a graph of the light source ratio showing the reflection spectrum intensity of the ceramic composite according to the present embodiment under a light source (3000K). FIG. 16 is a graph of the light source ratio showing the reflection spectrum intensity of the ceramic composite according to the present embodiment under a fluorescent lamp (visible light irradiation).

[0054] The vertical axis in FIGS. 13 to 16 indicates the reflection spectrum intensity (%) shown by the ceramic composite of the present embodiment, and the horizontal axis in each of the figures indicates the wavelength (nm).

[0055] Also, the graph line represented by the relatively thin solid line in FIG. 13 is the state where the ceramic composite of the present embodiment is placed under a light source (3000K), the thick solid line is the state where the ceramic composite of the present embodiment is heated to 200° C., and the broken line is the state where the ceramic composite of the present embodiment is placed at room temperature, respectively.

[0056] Also, the graph line represented by the relatively thin solid line in FIG. 14 is the state where the ceramic composite of the present embodiment is placed under a fluorescent lamp (visible light irradiation), the thick solid line is the state where the ceramic composite of the present embodiment is heated to 200° C., and the broken line is the state where the ceramic composite of the present embodiment is placed at room temperature, respectively.

[0057] Also, the graph line represented by the solid line in FIG. 15 shows the state where the ceramic composite of the present embodiment is heated to 200° C., and the broken line shows the state where the ceramic composite of the present embodiment is placed at room temperature, respectively.

[0058] Also, the graph line represented by the solid line in FIG. 16 shows the state where the ceramic composite of the present embodiment is heated to 200° C., and the broken line shows the state where the ceramic composite of the present embodiment is placed at room temperature, respectively.

[0059] The ceramic composite of the present embodiment shows a reflection spectrum intensity of 0.5% or more at wavelengths of 425 nm or more and 430 nm or less and 625 nm or more and 630 nm or less as shown in the reflection spectrum intensity graph of FIG. 14 at room temperature. Further, as shown in FIGS. 15 and 16, the reflection spectrum intensity at 425 nm or more and 485 nm or less is greater than the reflection spectrum intensity at wavelengths of 625 nm or more and 780 nm or less.

[0060] In the present invention, room temperature refers to a state where neither heating nor cooling is performed from the outside, and refers to a temperature range of 1° C. or more and 30° C. or less. The reflection spectrum intensity in the state where the ceramic composite of the present embodiment is placed within this temperature range is the reflection spectrum intensity at room temperature in FIGS. 13 to 16.

[0061] The ceramic composite placed at room temperature and before being heated has peaks in the reflection spectrum intensity at wavelengths of 425 nm or more and 430 nm or less and 625 nm or more and 630 nm or less as shown in FIG. 14, and has light absorption in other wavelength bands. Therefore, light absorption is recognized in a wide wavelength band in the ceramic composite of the present embodiment. Further, as shown in FIGS. 15 and 16, the reflection spectrum intensity in the purple to blue visible light wavelength band of 425 nm or more and 485 nm or less is greater than the reflection spectrum intensity in the red visible light wavelength band of wavelengths of 625 nm or more and 780 nm or less.

[0062] As shown in Fig. 14, the ceramic composite of the present embodiment placed at room temperature has light absorption throughout the visible light wavelength band except for wavelengths from 425 nm to 430 nm and from 625 nm to 630 nm, and is visually recognized as a light blue or light grayish blue color according to the reflection spectrum intensities shown in Figs. 15 and 16.

[0063] Next, Fig. 12 shows the appearance color of the ceramic composite of the present embodiment when heated from room temperature to 200 °C. Figs. 13 to 16 respectively show the reflection spectrum intensities of the ceramic composite heated to 200 °C.

[0064] When the ceramic composite according to the present embodiment is heated from room temperature to 200 °C, as shown in Figs. 13 to 16, the reflection spectrum intensity at wavelengths from 625 nm to 780 nm increases, while the reflection spectrum intensity at wavelengths from 425 nm to 485 nm decreases. Further, as shown in Fig. 14, the reflection spectrum intensity in the red visible light wavelength band at wavelengths from 625 nm to 650 nm shows 2.0% or more.

[0065] The ceramic composite heated to 200 °C has a weak absorption in the red visible light wavelength band at wavelengths from 625 nm to 780 nm, and a strong absorption in the violet to blue visible light wavelength band at wavelengths from 425 nm to 485 nm. Further, changes in the reflection spectrum intensity accompanying heating as shown in Figs. 13 to 16 occur. From the above, the ceramic composite of the present embodiment heated to 200 °C is visually recognized as a light pink color.

[0066] Although the heating temperature is shown as 200 °C, heating at least at 200 °C and up to 350 °C may also be acceptable. Also, the lower limit value of the heating temperature may be 150 °C or higher. By heating at 150 °C or higher and 350 °C or lower, in the ceramic composite of the present invention, the reflection spectrum intensity at wavelengths from 625 nm to 780 nm increases, while the reflection spectrum intensity at wavelengths from 425 nm to 485 nm decreases.

[0067] In the ceramic composite of the present invention, the change in the reflection spectrum intensity and the appearance color accompanying heating from room temperature to 150°C or higher and 350°C or lower is defined as thermochromism.

[0068] Examples of the heating method of the ceramic composite include a heating method by attaching it to a processing jig using an adhesive heated to 150°C or higher and 350°C or lower.

[0069] When the ceramic composite with a changed appearance color due to heating is placed as it is in a light-shielded state, the changed appearance color is retained. Even if the temperature of the ceramic composite of the present invention is lowered from 150°C or higher and 350°C or lower to the room temperature, the appearance color does not return to its original state in the light-shielded state. Therefore, only by lowering the temperature from 150°C or higher and 350°C or lower to the room temperature, the appearance color of the ceramic composite according to the present invention does not change and does not return to the original color, but in the present invention, it is defined as having thermochromism.

[0070] Next, in the state of the ceramic composite of the present invention that visually becomes a light pink color, light having any wavelength from 365 nm to 505 nm is irradiated onto the ceramic composite. Then, as shown in FIGS. 13 to 16, the reflection spectrum intensity at wavelengths from 625 nm to 780 nm decreases, and the reflection spectrum intensity at wavelengths from 425 nm to 485 nm increases. Further, as shown in FIG. 14, the reflection spectrum intensity at wavelengths from 425 nm to 430 nm and from 625 nm to 630 nm becomes 0.5% or more.

[0071] Examples of the light having any wavelength from 365 nm to 505 nm include ultraviolet light, fluorescent lamps capable of irradiating visible light, LED light sources, LD light sources, and the like.

[0072] Furthermore, the wavelength of the light irradiated on the ceramic composite is more preferably any one of 365 nm, 375 nm, 405 nm, 450 nm, and 505 nm. That is, it is either ultraviolet light (less than 380 nm and 365 nm) or a monochromatic light source of blue to green visible light. The reason for this preference is that the irradiated light enables the appearance color of the ceramic composite to return to its original light blue or light grayish blue color within a few seconds. That is, due to the irradiation of light, the reflection spectrum intensity in the ceramic composite changes to the reflection spectrum intensity at room temperature shown in FIGS. 13 to 16 within a few seconds.

[0073] Ultraviolet light sources (black lights), visible light sources (incandescent bulbs, fluorescent lights, LED light sources, LD light sources), and sunlight have wavelengths ranging from 365 nm to 505 nm. Therefore, even if it is not a monochromatic light source as described above, depending on the light intensity contained, the appearance color of the ceramic composite of the present invention returns to its original light blue or light grayish blue color in about 0.1 hour (6 minutes) to 24 hours.

[0074] In the ceramic composite of the present invention, the change in the reflection spectrum intensity and the appearance color accompanying the irradiation of the light is defined as photochromism. As described above, by irradiating the ceramic composite of the present invention with ultraviolet light, blue to green visible light, or fluorescent lights, LED light sources, or LD light sources, although the time varies, the appearance color of the ceramic composite changes. Therefore, in the present invention, it is defined as having photochromism.

[0075] If heated up to 350 °C, even if the irradiation of the light is repeated after heating, the appearance color of the ceramic composite according to the present invention changes repeatedly.

[0076] From the above, the ceramic composite according to the present invention can have both thermochromism and photochromism.

[0077] There are various possible uses for the ceramic composite of the present invention. For example, when using a material with thermochromism as a temperature marker in an electric furnace, the ceramic composite of the present invention used in a temperature environment of 150°C or higher and 350°C or lower can be instantaneously restored to its original state in a few seconds by irradiation with light having a wavelength of 365 nm or more and 505 nm or less and reused. In addition, even when left in a bright room, it can return to its original appearance color (light blue or light grayish blue) in about 30 minutes to 1 hour by light having a wavelength of 365 nm or more and 505 nm or less and can be reused.

[0078] As another use, it can be used for at least a part of experimental instruments, cooking utensils, etc. that are used at a temperature of 150°C or higher and 350°C or lower. As an example, by using the ceramic composite of the present invention for a part of a cooking utensil (for example, a tempura pan), it becomes possible to visually confirm whether the temperature of the oil is 150°C or higher based on the change in the appearance color due to the thermochromism of the ceramic composite. Furthermore, after using experimental instruments or cooking utensils, it becomes possible to visually confirm whether sterilization has been performed by ultraviolet light irradiation based on the change in the appearance color due to the photochromism of the ceramic composite.

[0079] Table 1 also shows the chromaticity Lab measurement results of the ceramic composite according to the present invention.

[0080]

Table 1

[0081] When the ceramic composite placed at room temperature and showing the light blue or light grayish blue appearance color is irradiated with light from a light source (3000K), the lightness L in the Lab color system is about 74.5 to 75, the chromaticity a is about -1.6 to -1.5, the chromaticity b is about -4.0 to -3.9, and the color difference ΔE is about 17 to 18.

[0082] When the ceramic composite placed at room temperature and showing the light blue or light grayish blue with a light appearance color is irradiated with visible light from a fluorescent lamp, the lightness L in the Lab color system is about 7.8 - 8, the chromaticity a is about -1.7 to -1.6, the chromaticity b is about -0.07 to -0.06, and the color difference ΔE is about 15 - 16.

[0083] On the other hand, when the ceramic composite heated to 200 °C and showing the light pink color with a light appearance color is irradiated with light from a light source (3000K), the lightness L in the Lab color system is about 84.1 - 84.2, the chromaticity a is about 8.5 - 8.6, the chromaticity b is about 6.7 - 6.8, and the color difference ΔE is about 17 - 18.

[0084] Also, when the ceramic composite heated to 200 °C and showing the light blue or light grayish blue with a light appearance color is irradiated with visible light from a fluorescent lamp, the lightness L in the Lab color system is about 13.0 - 13.1, the chromaticity a is about 8.8 - 8.9, the chromaticity b is about 10.2 - 10.3, and the color difference ΔE is about 15 - 16.

[0085] Since the variation in chromaticity is considered to indicate the variation in characteristics, it is preferable that the chromaticity can be adjusted within the above range.

[0086] Furthermore, from Table 1, the ceramic composite according to the present invention can have a color difference ΔE of 12.0 or more. The color difference ΔE can be represented by the following formula. ΔE = ((ΔL)×2+(Δa)×2+(Δb)×2)×(1 / 2). Here, ΔL, Δa, and Δb are the maximum values of the differences in the lightness L, chromaticity a, and chromaticity b of the ceramic composite, respectively. The lightness L, chromaticity a, and chromaticity b are measured at a predetermined number of measurement points of the ceramic composite, and the maximum of the differences is obtained to calculate the color difference ΔE. In the ceramic composite of the present invention, the color difference ΔE obtained as described above is all 12.0 or more. Thus, it is possible to make the color difference ΔE 12.0 or more, and it can be concluded that the color has changed to another color system.

[0087] Examples according to the present invention will be described below, but the present invention is not limited only to the following examples. EXAMPLES

[0088] The ceramic composite of this example was produced through each of the manufacturing steps of the above embodiment using the manufacturing apparatus based on the EFG method shown in Figures 1 to 6. Hereinafter, explanations that overlap with the above embodiment will be omitted or simplified, and the same reference numbers will be used. Furthermore, points that require new explanation will be explained with emphasis.

[0089] The crucible 5 was made of Mo, and a predetermined amount of raw material powder (powder containing 63.44 wt% aluminum oxide, 36.23 wt% yttrium oxide, and 0.33 wt% hafnium oxide) was placed into the crucible 5 containing the die 9 and heated to prepare a melt 21 and a melt reservoir 22.

[0090] Next, a ceramic composite seed crystal 17 was brought into contact with a melt pool 22 and pulled up to produce a ceramic composite 2. When the surface of the produced ceramic composite 2 was observed under a microscope, the image shown in FIG.

[0091] The oxide phase of the ceramic composite 2 contained HfO2 as a metal oxide, and the content of Hf was 0.1 at %.

[0092] At room temperature, the ceramic composite according to this example had a reflection spectrum intensity of 0.5% or more in the wavelengths of 425 nm to 430 nm and 625 nm to 630 nm, as shown in the reflection spectrum intensity graph in Fig. 14. Furthermore, as shown in Figs. 15 and 16, the reflection spectrum intensity of 425 nm to 485 nm was greater than the reflection spectrum intensity of 625 nm to 780 nm.

[0093] The ceramic composite placed at room temperature before heating had reflection spectrum intensity peaks at wavelengths of 425 nm to 430 nm and 625 nm to 630 nm, and had optical absorption in other wavelength bands, as shown in Fig. 14. Therefore, the ceramic composite of this example was recognized by the naked eye as a pale indigo or pale gray-blue color.

[0094] Next, when the ceramic composite according to this example was heated from room temperature to 200°C, as shown in FIGS. 13 to 16, the reflection spectrum intensity at wavelengths of 625 nm or more and 780 nm or less increased, and the reflection spectrum intensity at wavelengths of 425 nm or more and 485 nm or less decreased. Further, as shown in FIG. 14, the reflection spectrum intensity in the red visible light wavelength band of 625 nm or more and 650 nm or less was 2.0% or more.

[0095] The ceramic composite heated to 200°C had a weaker absorption in the red visible light wavelength band of 625 nm or more and 780 nm or less, and a stronger absorption in the violet to blue visible light wavelength band of 425 nm or more and 485 nm or less. Therefore, the ceramic composite of this example heated to 200°C was visually recognized as a light pink color.

[0096] The heating method of the ceramic composite of this example was a heating method by attaching it to a processing jig using an adhesive (wax) heated to 200°C.

[0097] When the ceramic composite with a changed appearance color due to heating was placed in a light-shielded state as it was, it was observed that the light pink appearance color was maintained even after two weeks.

[0098] Next, in the state of the ceramic composite of this example that was visually light pink, ultraviolet light having a wavelength of 375 nm and blue visible light having a wavelength of 450 nm were irradiated onto the ceramic composite. Then, as shown in FIGS. 13 to 16, the reflection spectrum intensity at wavelengths of 625 nm or more and 780 nm or less decreased, and the reflection spectrum intensity at wavelengths of 425 nm or more and 485 nm or less increased. Further, as shown in FIG. 14, the reflection spectrum intensity at wavelengths of 425 nm or more and 430 nm or less, and 625 nm or more and 630 nm or less was 0.5% or more. That is, it was confirmed that the irradiation of ultraviolet light or blue visible light caused the appearance color of the ceramic composite to return to the original light blue or light grayish blue color in a few seconds.

[0099] For comparison, as shown in Fig. 17, four samples of the ceramic composite were prepared, and each sample was irradiated with the ultraviolet light on a part thereof. As a result, as shown in Fig. 17, it was confirmed that only the middle part of the upper left sample, the upper right diagonal part of the upper right sample, the right half of the lower left sample, and the upper half of the lower right sample changed back from a light pink color to a light blue or light grayish blue color.

[0100] Also, the lightness L, chromaticity a, chromaticity b, and color difference ΔE in the Lab color system of the ceramic composite according to this example are as shown in Table 1. In the ceramic composite of this example, the color difference ΔE obtained as described above is all 12.0 or more, and it is concluded that the color has changed to another color system.

[0101] Furthermore, as another example, the ceramic composite that visually became a light pink color was irradiated with light having a visible light wavelength from a fluorescent lamp. Then, it was confirmed that the appearance color of the ceramic composite returned to the original light blue or light grayish blue color in 1 hour.

Explanation of Reference Numerals

[0102] 1... Manufacturing apparatus 2... Ceramic composite 3... Growth container 4... Lifting container 5... Crucible 6... Crucible drive unit 7... Heater 8... Electrode 9... Die 10... Heat insulator 11... Atmosphere gas inlet 12... Exhaust port 13... Shaft 14... Shaft drive unit 15... Gate valve 16... Substrate entrance / exit 17... Seed crystal 18... Partition plate 19... Slit 20... Opening 21... Melt 22... Melt reservoir 23... Notch 24... Notch hole 26... straight barrel part 28... side surface of the seed crystal 30... inclined plane

Claims

1. At least Y ３ Al ５ O １２ phase and Al ２ O ３ has two oxide phases of the phase as a lamellar structure, containing 0.1 at% of Hf, when heated from room temperature to at least 200 °C, the reflection spectrum intensity at wavelengths of 625 nm or more and 780 nm or less increases, and the reflection spectrum intensity at 425 nm or more and 485 nm or less decreases, and then, when irradiated with light having any wavelength of 365 nm or more and 505 nm or less, the reflection spectrum intensity at wavelengths of 625 nm or more and 780 nm or less decreases, and the reflection spectrum intensity at 425 nm or more and 485 nm or less increases, a ceramic composite.

2. The ceramic composite according to claim 1, wherein the wavelength of the light is any one of 365 nm, 375 nm, 405 nm, 450 nm, and 505 nm.

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