Negative thermal expansion material, composite material, and method for manufacturing negative thermal expansion material

Abstract

Negative thermal expansion materials with a negative coefficient of thermal expansion are made of Zr 2‑ a M a S x P2O 12+δ The expression indicates that M is at least one selected from Ti, Ce, Sn, Mn, Hf, Ir, Pb, Pd, and Cr; a is 0 ≤ a < 2; x is 0.4 ≤ x ≤ 1; and δ is defined as a value that satisfies the charge neutrality condition. This invention enables the provision of a negative thermal expansion material, a composite material, and a method for manufacturing a negative thermal expansion material, achieving cost and density reduction.

Description

Technical Field

[0001] This invention relates to a negative thermal expansion material, a composite material, and a method for manufacturing a negative thermal expansion material. Background Technology

[0002] In devices such as electronic equipment, optical devices, fuel cells, and sensors, where multiple materials are used in combination, misalignment due to thermal expansion can cause problems. Furthermore, severe failures such as interface delamination and breakage can occur due to differences in the coefficients of thermal expansion of the materials. Therefore, various near-zero thermal expansion materials and thermal expansion control techniques have been investigated. For example, invar alloys, glass, and cordierite are widely known as single-phase near-zero thermal expansion materials and are used in industrial and consumer products. Recently, attempts have been made to reduce the thermal expansion of substances with difficult-to-control coefficients of thermal expansion by combining them with fillers having low coefficients of thermal expansion. In particular, the combination with materials having negative coefficients of thermal expansion (hereinafter also referred to as negative thermal expansion materials) has attracted attention because this material can effectively counteract thermal expansion even at low mixing ratios.

[0003] Patent document 1 discloses a method using Bi 1-x Sb x NiO3 (where x is 0.02≤x≤0.20) represents a material with a negative coefficient of thermal expansion.

[0004] Citation List

[0005] Patent documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-48071 Summary of the Invention

[0007] Technical issues

[0008] Various materials with negative coefficients of thermal expansion have been reported to date. However, many of these materials contain precious and heavy metals as their main components. Therefore, cost and density reductions have not yet been achieved.

[0009] In view of the above problems, the purpose of this invention is to provide a negative thermal expansion material, a composite material, and a method for manufacturing a negative thermal expansion material, which can reduce cost and density.

[0010] Solution to the problem

[0011] The negative thermal expansion material with a negative thermal expansion coefficient according to the present invention is characterized by being composed of Zr 2-a M a Sx P2O 12+δ The expression is given by, where M is at least one of Ti, Ce, Sn, Mn, Hf, Ir, Pb, Pd and Cr; a is 0 ≤ a < 2; x is 0.4 ≤ x ≤ 1; and δ is defined as a value that satisfies the charge neutrality condition.

[0012] The composite material according to the present invention is characterized in that it comprises a negative thermal expansion material as described above and a material having a positive thermal expansion coefficient.

[0013] The method for manufacturing a negative thermal expansion material according to the present invention comprises: a step of hydrothermally treating a mixture containing zirconium oxychloride octahydrate, ammonium phosphate, and sulfuric acid at a temperature of 130°C or higher; and a step of baking the hydrothermally treated mixture at a temperature of 450°C or higher to form a Zr₂S₂ mixture. x P2O 12+δ (where 0.4≤x≤1, and δ is defined as a value that satisfies the charge neutrality condition) represents the steps of a material having a negative coefficient of thermal expansion.

[0014] The method for manufacturing a negative thermal expansion material according to the present invention comprises: a step of hydrothermally treating a mixture containing zirconium oxychloride octahydrate, ammonium phosphate, sulfuric acid, and an additive containing element M at a temperature of 130°C or higher; and a step of baking the hydrothermally treated mixture at a temperature of 450°C or higher to form a material composed of Zr. 2-a M a S x P2O 12+δ (where M is at least one of Ti, Ce, Sn, Mn, Hf, Ir, Pb, Pd and Cr; a is 0 ≤ a < 2; x is 0.4 ≤ x ≤ 1; and δ is a value defined as satisfying the charge neutrality condition) represents the steps of a material having a negative coefficient of thermal expansion.

[0015] Beneficial effects of the invention

[0016] This invention enables the provision of a negative thermal expansion material, a composite material, and a method for manufacturing a negative thermal expansion material, which can reduce cost and density. Attached Figure Description

[0017] Figure 1A This is a graph showing the temperature characteristics of the negative thermal expansion material according to the present invention.

[0018] Figure 1B This is a graph showing the temperature characteristics of the negative thermal expansion material according to the present invention.

[0019] Figure 1C This is a graph showing the temperature characteristics of the negative thermal expansion material according to the present invention.

[0020] Figure 2A flowchart of a method for manufacturing a negative thermal expansion material according to the present invention is shown.

[0021] Figure 3 A table showing the baking conditions and atomic ratios of the samples is presented.

[0022] Figure 4 The graph shows the relationship between baking temperature and S atomic content.

[0023] Figure 5 This is a graph showing the XRD measurement results of the sample.

[0024] Figure 6A This is a graph showing the relationship between 2S / Zr and the lattice constant.

[0025] Figure 6B This is a graph showing the relationship between 2S / Zr and the lattice constant.

[0026] Figure 7A A photograph of the FE-SEM image of sample 4 is shown.

[0027] Figure 7B A photograph of the FE-SEM image of sample 4 is shown.

[0028] Figure 8 This is a graph showing the XRD measurement results of the sample (hydrothermal treatment temperature: 110℃).

[0029] Figure 9 This is a graph showing the XRD measurement results of the sample (hydrothermal treatment temperature: 130℃).

[0030] Figure 10 This is a graph showing the XRD measurement results of the sample (hydrothermal treatment temperature: 180℃).

[0031] Figure 11 This is a graph showing the XRD measurement results of the sample (hydrothermal treatment temperature: 230℃).

[0032] Figure 12 The graph shows the relationship between the baking temperature and the S atomic content of samples that have undergone hydrothermal treatment at their respective temperatures.

[0033] Figure 13A This is a photograph of the FE-SEM image of sample 11 (hydrothermal treatment temperature: 110℃).

[0034] Figure 13B A photograph of the FE-SEM image of sample 19 (hydrothermal treatment temperature: 180°C) is shown.

[0035] Figure 14 A flowchart illustrating the manufacturing method of a negative thermal expansion material is shown.

[0036] Figure 15 The XRD measurements of the sample obtained by replacing some Zr sites with Ti are shown.

[0037] Figure 16 The Zr shown is used in practice. 2-a Ti a SP2O 12 The table is composed of [variables].

[0038] Figure 17 It shows Zr 2-a Ti a SP2O 12 A graph showing the temperature characteristics.

[0039] Figure 18 This is a graph showing the relationship between Ti content and cell volume.

[0040] Figure 19 It is a concentrated display of Zr 2-a Ti a SP2O 12 A graph showing the coefficients of thermal expansion within their respective temperature ranges.

[0041] Figure 20 This is a graph showing the XRD measurements of a sample obtained by replacing some Zr sites with Ce.

[0042] Figure 21 It shows Zr 2-a Ce a SP2O 12 A graph showing the temperature characteristics.

[0043] Figure 22 This is a graph showing the XRD measurements of a sample obtained by replacing some Zr sites with Mn.

[0044] Figure 23 It shows Zr 2-a Mn a SP2O 12 A graph showing the temperature characteristics.

[0045] Figure 24 This is a graph showing the XRD measurement results of a sample obtained by replacing some Zr sites with Sn.

[0046] Figure 25 It shows Zr 2-a Sn a SP2O 12 A graph showing the temperature characteristics.

[0047] Figure 26 This is a graph showing the coefficients of thermal expansion of samples obtained by replacing some Zr sites with Ce, Mn, and Sn in their respective temperature ranges.

[0048] Figure 27 A flowchart illustrating the manufacturing method of a negative thermal expansion material is shown.

[0049] Figure 28 This is a graph showing the XRD measurements of a sample obtained by replacing some S sites with Mo.

[0050] Figure 29 This is a graph showing the XRD measurements of a sample obtained by replacing some S sites with Mo.

[0051] Figure 30 It shows Zr2S 1-b Mo b P2O 12 A graph showing the temperature characteristics.

[0052] Figure 31 It shows Zr2S 1-b Mo b P2O 12 A graph showing the temperature characteristics.

[0053] Figure 32 This is a graph showing the XRD measurement results of a sample obtained by replacing part of the S sites with W.

[0054] Figure 33 This is a graph showing the XRD measurement results of a sample obtained by replacing some S sites with W.

[0055] Figure 34 It shows Zr2S 1-b W b P2O 12 A graph showing the temperature characteristics.

[0056] Figure 35 It shows Zr2S 1-b W b P2O 12 A graph showing the temperature characteristics. Detailed Implementation

[0057] Embodiments of the present invention will now be described.

[0058] The negative thermal expansion material according to the embodiment is characterized by: being composed of Zr 2-a M a S x P2O 12+δThe expression is given by, where M is at least one of Ti, Ce, Sn, Mn, Hf, Ir, Pb, Pd and Cr; a is 0 ≤ a < 2; x is 0.4 ≤ x ≤ 1; and δ is defined as a value that satisfies the charge neutrality condition.

[0059] For example, if a = 0, then the negative thermal expansion material is Zr2S x P2O 12+δ The material is represented by a. Conversely, if a≠0, the negative thermal expansion material is obtained by replacing part of the Zr sites with M.

[0060] For example, if M is Ti, then the negative thermal expansion material is made of Zr. 2-a Ti a S x P2O 12+δ The material represented, wherein a is preferably 0 <a≤0.7。

[0061] If M is Ce, then the negative thermal expansion material is made of Zr. 2-a Ce a S x P2O 12+δ The material represented, wherein a is preferably 0 <a≤0.4。

[0062] If M is Sn, then the negative thermal expansion material is made of Zr. 2-a Sn a S x P2O 12+δ The material represented, wherein a is preferably 0 <a≤1。

[0063] If M is Mn, then the negative thermal expansion material is made of Zr. 2-a Mn a S x P2O 12+δ The material represented, wherein a is preferably 0 <a≤0.2。

[0064] In addition, the element M that replaces part of the Zr site can be Hf, Ir, Pb, Pd, and Cr.

[0065] In the implementation method, Zr 2-a M a S x P2O 12+δ The S sites of the material with negative thermal expansion can be replaced by Mo or W.

[0066] In implementation, some P sites may be further replaced by elements such as V, Mn, Cr, As and Nb.

[0067] As described above, the negative thermal expansion material according to the embodiment is mainly composed of inexpensive and relatively light atoms. Therefore, it is possible to reduce the cost and density of the negative thermal expansion material.

[0068] Now, the negative thermal expansion material according to the embodiments will be described in more detail. In the following embodiments, as examples, Zr2S will be described. x P2O 12+δ Let and , where 0.4 ≤ x ≤ 1; and δ is a material defined as satisfying the charge neutrality condition. In the implementation, Zr 2-a M a S x P2O 12+δ Other materials with negative thermal expansion exhibit the same properties.

[0069] Figures 1A to 1C It shows the Zr2S x P2O 12+δ A graph showing the temperature characteristics of a material with negative thermal expansion.

[0070] Figure 1A The temperature characteristics of the lattice constant of axis (b) are shown; Figure 1B The temperature characteristics of the lattice constant along the c-axis are shown; and Figure 1C The temperature characteristics of the unit cell volume are shown. Note that since the negative thermal expansion material according to this embodiment is a rhombohedral crystal system, the lengths of the a-axis and b-axis are equal.

[0071] like Figures 1A to 1C As shown, the coefficient of thermal expansion of the negative thermal expansion material according to this embodiment varies depending on the value of x, i.e., the content of sulfur atoms (S). For example, if the value of x is 0.48 ≤ x ≤ 0.9, then at temperatures between 100 and 180°C, the absolute value of the volumetric expansion coefficient of the negative thermal expansion material is higher than the absolute value of the volumetric expansion coefficient at temperatures exceeding 180°C. In other words, if the value of x is 0.48 ≤ x ≤ 0.9, then the cell volume changes drastically within the temperature range of 100°C to 180°C. Within this temperature range, the c-axis contracts drastically, while the a-axis expands, resulting in a drastic contraction of the entire lattice volume.

[0072] As an example, if x = 0.48, the volumetric expansion coefficient (100 to 180°C) of the negative thermal expansion material according to this embodiment is -94 ppm / °C; if x = 0.54, the volumetric expansion coefficient is -101 ppm / °C; if x = 0.76, the volumetric expansion coefficient is -101 ppm / °C; and if x = 0.90, the volumetric expansion coefficient is -108 ppm / °C. As the value of x increases, the volumetric expansion coefficient (100 to 180°C) tends to decrease.

[0073] Focusing on the case where x = 0.90, the volume expansion coefficient is -26 ppm / ℃ in the range of 30 to 100℃; -108 ppm / ℃ in the range of 100 to 180℃; -8.1 ppm / ℃ in the range of 180 to 350℃; and -13 ppm / ℃ in the range of 350 to 500℃.

[0074] If the value of x is 0.4 ≤ x < 0.48, then the coefficient of volumetric expansion of the negative thermal expansion material becomes almost constant above 80℃ (see...). Figure 1C (x = 0.43). In other words, if the value of x is 0.4 ≤ x < 0.48, the volume shrinkage from 80°C to 180°C is low compared to the volume shrinkage of other samples. As a result, the coefficient of volume expansion becomes almost constant above 80°C. Focusing on the case of x = 0.43, the coefficient of volume expansion reaches an almost constant value of -16 ppm / °C above 80°C.

[0075] As described above, the negative thermal expansion material according to this embodiment has a negative coefficient of thermal expansion in the range of room temperature to 500°C. In particular, if the value of x is 0.48 ≤ x ≤ 0.9, a large negative coefficient of thermal expansion is exhibited in the range of 100 to 180°C. The magnitude of the coefficient of thermal expansion decreases as the sulfur atom (S) content decreases. Conversely, if the value of x is 0.4 ≤ x < 0.48, the volumetric expansion coefficient of the negative thermal expansion material becomes almost constant above 80°C.

[0076] According to this embodiment, the crystal phase of the negative thermal expansion material is α-Zr2SP2O. 12 (ICDD card number: 04-017-0937) indicates that it may contain another crystalline phase, for example, in addition to the α phase (α-Zr2SP2O). 12 In addition to the β phase (β-Zr2SP2O), it may also contain a portion of the β phase. 12 (ICDD card: 04-007-8019)

[0077] The negative thermal expansion material (Zr2S) according to this embodiment constitutes x P2O 12+δ The atoms in this material are Zr, S, and P. Because these materials are inexpensive, negative thermal expansion materials can be formed much more cheaply compared to traditional negative thermal expansion materials made from precious metals. Therefore, the cost of negative thermal expansion materials can be reduced.

[0078] The negative thermal expansion material (Zr2S) according to this embodiment constitutes x P2O 12+δThe atoms in this material are Zr, S, and P. Because these atoms (especially S and P) are relatively lightweight, the density of negative thermal expansion materials can be reduced compared to conventional negative thermal expansion materials. Therefore, a reduction in the density of negative thermal expansion materials can be achieved.

[0079] For example, the density of the negative thermal expansion material Mn-Sn-Zn-N (Smartec: a registered trademark) is approximately 7 g / cm³. 3 Zr2WP2O 12 The density of the material with negative thermal expansion is 3.86 g / cm³. 3 And Zr2MoP2O 12 Its density is 3.36 g / cm³. 3 Conversely, Zr2SP2O 12 The density of the negative thermal expansion material according to this embodiment is 3.02 g / cm³. 3 This density is lower than that of traditional negative thermal expansion materials.

[0080] Composite materials with controlled coefficients of thermal expansion are formed by mixing materials with negative thermal expansion coefficients and materials with positive thermal expansion coefficients (positive thermal expansion materials). In other words, they are formed by dispersing the negative thermal expansion material within the positive thermal expansion material. In this case, if the density of the negative thermal expansion material is reduced, it can be uniformly dispersed within the positive thermal expansion material.

[0081] As described above, the coefficient of thermal expansion of the negative thermal expansion material according to this embodiment varies depending on the value x, i.e., the sulfur atom S content. More specifically, if the value x is 0.48 ≤ x ≤ 0.9, the material exhibits a large negative coefficient of thermal expansion in the range of 100 to 180°C. As the sulfur atom S content decreases, the magnitude of the negative coefficient of thermal expansion decreases. If the value x is 0.4 ≤ x < 0.48, the volumetric expansion coefficient of the negative thermal expansion material becomes almost constant above 80°C.

[0082] In this embodiment, the value x of the negative thermal expansion material is preferably determined based on the characteristics of the positive thermal expansion material to be used to form the composite material, the characteristics of the composite material to be formed, and the temperature range of the composite material to be used.

[0083] For example, if the material with positive thermal expansion is a resin material, then considering the operating temperature (heat resistance temperature) of the resin material, the value x of the material with negative thermal expansion is preferably set to 0.48 ≤ x ≤ 0.9. In other words, considering the heat resistance temperature of the resin material, it is assumed that the operating temperature of the resin material is from room temperature to 200°C. Furthermore, if the value x is 0.48 ≤ x ≤ 0.9, a large negative coefficient of thermal expansion is exhibited in the range of 100 to 180°C. Therefore, if the value x of the material with negative thermal expansion is specified as 0.48 ≤ x ≤ 0.9, the operating temperature range of the resin material overlaps with the range in which the material with negative thermal expansion exhibits a large negative coefficient of thermal expansion, resulting in effective control of the coefficient of thermal expansion of the composite material.

[0084] If the material with positive thermal expansion is a metal, considering the operating temperature (heat resistance temperature) of the metal, the value x for the material with negative thermal expansion is preferably set to 0.4 ≤ x < 0.48. In other words, composite materials containing metal are mainly used over a wide operating temperature range. If the value x is 0.4 ≤ x < 0.48, the volumetric expansion coefficient of the material with negative thermal expansion becomes almost constant above 80°C. Therefore, if the value x for the material with negative thermal expansion is set to 0.4 ≤ x < 0.48, the operating temperature range of the composite material containing metal can roughly overlap with the range where the volumetric expansion coefficient of the material with negative thermal expansion becomes almost constant, resulting in effective control of the coefficient of thermal expansion of the composite material.

[0085] Note that the above construction is only one embodiment. In this embodiment, if the positive thermal expansion material is a metallic material, a composite material can be formed by using a negative thermal expansion material with a value x set to 0.48 ≤ x ≤ 0.9. If the positive thermal expansion material is a resin material, a composite material can be formed by using a negative thermal expansion material with a value x set to 0.4 ≤ x < 0.48. More specifically, in this embodiment, the value x of the negative thermal expansion material can be determined taking into account, for example, the temperature range of the composite material used and the characteristics of the positive thermal expansion material to be mixed.

[0086] Now, refer to Figure 2 The flowchart shown describes the negative thermal expansion material (Zr2S) according to this embodiment. x P2O 12+δ The method for manufacturing zirconium oxychloride (ZrCl₂O·8H₂O), ammonium phosphate, and sulfuric acid (H₂SO₄) are first prepared as raw materials. The ammonium phosphate that can be used in this paper is selected from at least one of ammonium dihydrogen phosphate (NH₄H₂PO₄) and diammonium hydrogen phosphate ((NH₄)₂HPO₄). After dissolving ZrCl₂O·8H₂O and NH₄H₂PO₄ in distilled water, sulfuric acid is mixed into their aqueous solution, and the mixture is stirred for a predetermined time (step S1).

[0087] After stirring, the resulting aqueous solution (mixture) is subjected to hydrothermal treatment at a temperature of 130°C or higher, preferably 180°C or higher (step S2). The hydrothermal treatment time is specified to be 0.5-4 days. After the predetermined hydrothermal treatment time, the mixture (after hydrothermal treatment) is dried (step S3). More specifically, after hydrothermal treatment, a white precipitate is formed in the container. The solution (mixture) containing the white precipitate is poured into an evaporating dish and heated through a heater at approximately 100°C to evaporate excess water (first drying process). At this point, since the mixture cannot be completely dried due to the presence of excess sulfuric acid, the evaporating dish is placed in an electric furnace at 300°C, and a second drying process is then performed (step S4).

[0088] After the second drying process is completed, the (dried) mixture is baked at a temperature above 450°C to form a material with a negative coefficient of thermal expansion, represented by the above general formula (step S5). The temperature used for baking the mixture can be set, for example, above 450°C and below 900°C. During the baking process, the value x in the above general formula can be controlled by controlling the temperature used for baking the dried mixture. More specifically, as the baking temperature increases, sulfur (S) is more easily removed, and the sulfur-S content ratio in the above formula decreases. At this time, the value x in the above general formula (i.e., the S content) can be controlled by controlling the baking time.

[0089] In this embodiment, since the negative thermal expansion material is manufactured using a hydrothermal method, it can be produced at low cost. Although details will be described later, the use of a hydrothermal method allows for a narrower particle size distribution of the negative thermal expansion material. As described above, because the particle size distribution of the negative thermal expansion material is narrowed, it can be uniformly dispersed within the positive thermal expansion material.

[0090] When the manufacturing method of the negative thermal expansion material according to this embodiment is used, cubic particles of 200 to 300 nm can be formed on the side surface of the negative thermal expansion material (see Figure 7). More specifically, since the particle size of the negative thermal expansion material can be reduced, the surface roughness of the composite material can be reduced if the negative thermal expansion material and the positive thermal expansion material are mixed to form a composite material.

[0091] Note that the manufacturing methods mentioned above are used to manufacture Zr2S x P2O 12+δ The material represented by (i.e., a = 0). From Zr 2- a M a S x P2O 12+δThe material represented by (0 < a < 2) can be manufactured as follows: In the mixed raw materials in step S1, in addition to zirconium oxychloride octahydrate, ammonium sulfate, and sulfuric acid, a material (additive) containing element M is added. For example, if M is Ti, titanium(IV) sulfate solution (Ti(SO4)2) is added. If M is Ce, cerium(IV) sulfate tetrahydrate (Ce(SO4)2·4H2O) is added. If M is Sn, tin oxide (SnO2) is added. If M is Mn, manganese dioxide (MnO2) is added. Note that these additives are only examples. Materials (additives) other than these can be used as long as they can add element M to the negative thermal expansion material.

[0092] As described above, in the present embodiment, the part of the S site of the negative thermal expansion material represented by Zr 2-a M a S x P2O 12+δ can be replaced by Mo or W. In this case, a material (additive) containing element Mo or element W is added during the manufacturing process. In this way, part of the S site can be replaced by Mo or W.

[0093] Examples

[0094] Now, examples of the present invention will be described.

[0095] Hereinafter, examples of the following negative thermal expansion materials will be described.

[0096] (1) Zr2S x P2O 12+δ

[0097] (2) Zr 2-a Ti a S x P2O 12+δ (Part of the Zr site is replaced by Ti)

[0098] (3) Zr 2-a Ce a S x P2O 12+δ (Part of the Zr site is replaced by Ce)

[0099] (4) Zr 2-a Sn a S x P2O 12+δ (Part of the Zr site is replaced by Sn)

[0100] (5) Zr 2-a Mn a S x P2O 12+δ (Part of the Zr site is replaced by Mn)

[0101] (6)Zr2S 1-b Mo b P2O 12+δ (Some Zr sites were replaced by Mo)

[0102] (7)Zr2S 1-b W b P2O 12+δ (Some Zr sites were replaced by W)

[0103] <(1)Zr2S x P2O 12+δ >

[0104] (Preparation and evaluation of negative thermal expansion materials)

[0105] First, in order to examine the Zr2S x P2O 12+δ Samples 1-9 were prepared based on the relationship between the composition of the negative thermal expansion material according to the present invention and its coefficient of thermal expansion, represented by (0.4≤x≤1, and δ is defined as a value satisfying the charge neutrality condition). Samples 1-9 are prepared according to... Figure 2 The flowchart shown is used to prepare it.

[0106] More specifically, first, prepare the raw materials ZrCl₂O·8H₂O (Wako special grade, Wako Pure Chemicals Co., Ltd. (now Fujifilm), NH₄H₂PO₄ (reagent grade, Wako Pure Chemicals Co., Ltd.), and H₂SO₄ (reagent grade, Wako Pure Chemicals Co., Ltd.). Then, dissolve ZrCl₂O·8H₂O and NH₄H₂PO₄ separately in distilled water to a concentration of 0.8 M. Subsequently, mix these aqueous solutions (10 ml each) with 3 ml of H₂SO₄. Stir the mixture for 90 minutes using a stirrer (step S1).

[0107] After stirring, the aqueous solution (mixture) is poured into a container made of Teflon (registered trademark) (HUT-100, SAN-AI Kagaku Co., Ltd.), and this container is placed inside an outer cylinder made of pressure-resistant stainless steel (HUS-100, SAN-AI Kagaku Co., Ltd.). The cylinder is then placed in a hot air circulating oven (KLO-45M, Koyo Thermo Systems Co., Ltd.) and heated. Hydrothermal treatment (step S2) is performed in this manner. The hydrothermal treatment is carried out at 180°C for 4 days.

[0108] After hydrothermal treatment, the removed Teflon container contained a white precipitate. The solution containing the precipitate was poured into an evaporating dish and heated on a heater at approximately 100°C to evaporate excess moisture (step S3: first drying process). At this point, the sample was not completely dried due to the presence of excess H2SO4 and residual moisture. Therefore, the evaporating dish containing the sample was placed in an electric furnace (KDF-S80, DENKEN-HIGHDENTAL Ltd.) at 300°C and further dried for 12 hours (step S4: second drying process). Afterward, the sample (dried at 300°C) was placed in an electric furnace (KDF-S80, DENKEN-HIGHDENTAL Ltd.) and baked at 400-900°C for 4 hours or 12 hours. In this way, white powder samples 1-9 were obtained (step S5).

[0109] The composition (atomic ratio) of samples 1-9 prepared in this manner was analyzed by ICP-OES (inductively coupled plasma optical emission spectrometry).

[0110] [ICP-OES]

[0111] • ICP-OES equipment used: 5100VDV ICP-OES (Agilent Technologies)

[0112] • ICP ionization unit: Ar plasma

[0113] A concentration calibration curve for the atoms in the solution was prepared using standard solutions of Zr, P, and S (all manufactured by Wako Pure Chemicals Co., Ltd.) from samples 1-9. The concentration of atoms completely dissolved in the mixed acid (0.5% HF + 5% HNO3) was measured.

[0114] Figure 3 The relationship between baking conditions and atomic ratios for samples 1-9 is shown. In samples 1-9, the atomic ratio of Zr is the same (value 2). The atomic ratios of P are almost identical (1.8-2). Conversely, the atomic ratio of S varies depending on the baking conditions of samples 1-9.

[0115] To be more specific, the atomic ratio of sulfur (S) was 1.6 in Sample 1 (dried only once at 300°C). In Sample 2 (baking conditions: 400°C, 4 hours), the atomic ratio of S was 1.2. In Sample 3 (baking conditions: 450°C, 4 hours), the atomic ratio of S was 1. In Sample 4 (baking conditions: 500°C, 4 hours), the atomic ratio of S was 0.90. In Sample 5 (baking conditions: 500°C, 12 hours), the atomic ratio of S was 0.76. In Sample 6 (baking conditions: 600°C, 4 hours), the atomic ratio of S was 0.54. In Sample 7 (baking conditions: 700°C, 4 hours), the atomic ratio of S was 0.48. In Sample 8 (baking conditions: 800°C, 4 hours), the atomic ratio of S was 0.44. In Sample 9 (baking conditions: 900°C, 4 hours), the atomic ratio of S was 0.43.

[0116] Figure 4 This is a graph showing the relationship between baking temperature and sulfur atomic content (atomic ratio). Figure 4 In the middle, it was drawn Figure 3 The table shown is a plot of the baking temperature versus the atomic ratio of S (atoms) for samples 1-4 and 6-9. (See table for example.) Figure 4 As shown, the sulfur (S) content decreases with increasing baking temperature. This is because it becomes easier to remove S from the samples with increasing baking temperature. Figure 4 The results showed that the S content in the sample, in other words, Zr2S x P2O 12+δ The value of x can be controlled by adjusting the baking temperature.

[0117] When comparing samples 4 and 5, the atomic ratio of sulfur (S) in sample 4 (baking conditions: 500℃, 4 hours) was 0.90, while the atomic ratio of sulfur in sample 5 (baking conditions: 500℃, 12 hours) was 0.76. This result indicates that the sulfur content decreases with increasing baking time. Therefore, it was found that the sulfur content in the samples can be controlled by adjusting the baking time.

[0118] To determine the crystal structure of samples 1-9, X-ray diffraction measurements (XRD) were performed.

[0119] [XRD]

[0120] • Equipment used: XRD-6100 (Shimadzu Corporation)

[0121] Atmosphere: air

[0122] • Tube current / tube voltage: 30mA / 40kV

[0123] Target: Cu

[0124] • Step size: 0.02°

[0125] • Measurement range (scanning speed): 10-70° (1° / min)

[0126] The XRD measurement results of samples 1-9 are as follows Figure 5 As shown. Figure 5 As shown, α-Zr2SP2O was observed in all samples 1-9. 12 (ICDD Card No.: 04-017-0937) phase. In samples 7-9 obtained by baking at temperatures above 700°C, a broad peak was observed near 30.5°. This is likely the peak of ZrO2. XRD measurements indicate that a suitable baking temperature of 450-600°C is appropriate for obtaining single-phase α-Zr2SP2O. 12 .

[0127] The correlation between S content and lattice constant was investigated using XRD measurements. Figure 6A and Figure 6B A plot showing the calculated lattice constant of the sample relative to S (the ratio of 2S normalized to Zr) is presented. Figure 6A In the diagram, the vertical axis represents the lattice constant of the a-axis; while Figure 6B The vertical axis represents the lattice constant of the c-axis. For example... Figure 6A and Figure 6B As shown, as the S content decreases by half from 1.0 to 0.48, the lattice constants of both the a-axis and c-axis decrease linearly. This trend conforms to Vegard's law and indicates that even with a 50% reduction in S content (0.48), the lattice constants of α-Zr₂SP₂O₃ remain constant. 12 It also exists as a solid solution. However, when the S content decreases to 0.44 or 0.43, the graph deviates from Vigarde's law. The lattice constant along the a-axis increases, but the lattice constant along the c-axis shrinks sharply. This indicates a sharp contraction in the unit cell volume. These results suggest that if the S content decreases to around 0.4, it indicates that the S content exceeds the lower limit (amount) for solid solution formation, and α-Zr₂S… x P2O 12 The phase is decomposed. Considering the XRD measurements of samples 8 and 9, ZrO2 peaks were observed, indicating that samples with S contents of 0.44 and 0.43 may be in the α-Zr2SP2O phase. 12 The state in which it coexists with ZrO2.

[0128] The coefficients of thermal expansion of samples 1-9 were measured by the following method.

[0129] The following powder X-ray diffractometer was equipped with a benchtop heated stage (BTS 500, Anton Paar) and X-ray diffraction patterns were obtained at arbitrary temperatures. Note that a high-speed one-dimensional detector (D / teX Ultra2, Rigaku, Japan) was used as the detector, and measurements were performed under the following conditions. Si (NISTSRM 640c) was used as an internal standard.

[0130] [High Temperature XRD]

[0131] • Equipment used: Mini Flex 600 (Company: Rigaku)

[0132] Atmosphere: air

[0133] • Tube current / tube voltage: 15mA / 40kV

[0134] Target: Cu

[0135] • Step size: 0.02°

[0136] • Measurement range (scanning speed): 10-80° (4° / min)

[0137] • Measurement temperature: 30-500℃ (in 20℃ intervals within the range of 80-220℃, and in 50℃ intervals above 250℃)

[0138] Using the obtained X-ray diffraction pattern and analysis software (HighScore Plus, PANalytical), the crystal structure was refined according to the Rietveld method, and the lattice constant was calculated. A plot of the lattice constant versus temperature was then drawn. Successfully applied within the temperature range of the linear approximation, the linear thermal expansion coefficient α of each crystal axis was calculated according to the following expression. l and the coefficient of volumetric thermal expansion α v .

[0139] [Expression 1]

[0140]

[0141] [Expression 2]

[0142]

[0143] Figures 1A to 1C The linear thermal expansion coefficient and volumetric thermal expansion coefficient of each crystal axis are shown. For example... Figure 1C As shown, α-Zr2SP2O was found 12The volume changes drastically from 100℃ to 180℃. Within this temperature range, the c-axis contracts sharply while the a-axis expands, resulting in a sharp contraction of the entire lattice volume. When calculating the coefficient of thermal expansion of sample 4 (x = 0.90), the linear coefficient of thermal expansion along the a-axis (100 to 180℃) is +79 ppm / ℃; while the linear coefficient of thermal expansion along the c-axis (within the same temperature range) is -263 ppm / ℃. Therefore, its volumetric coefficient of thermal expansion (within the same temperature range) is -108 ppm / ℃.

[0144] When comparing samples 6 (x = 0.54) and 7 (x = 0.48) with sample 4 (x = 0.90), the following trend was observed: volume change decreased with increasing baking temperature and decreasing sulfur content. The coefficient of volumetric thermal expansion (100-180℃) for sample 6 (x = 0.54) was -101 ppm / ℃, while that for sample 7 (x = 0.48) was -94 ppm / ℃. The coefficient of volumetric thermal expansion for sample 5 (x = 0.76) baked for a long time (within the same temperature range as above) was -101 ppm / ℃. When this value was compared with the coefficient of volumetric thermal expansion of sample 4 (x = 0.90), a small volume change was observed.

[0145] In the measurements, when sample 9 (x = 0.43) was compared with other samples, it exhibited low volume shrinkage within the temperature range of 100°C to 180°C. In sample 9 (x = 0.43), the linear coefficient of thermal expansion along the a-axis (100–180°C) was +8.3 ppm / °C, while the linear coefficient of thermal expansion along the c-axis (within the same temperature range) was -44 ppm / °C. Based on these, the calculated bulk thermal expansion coefficient (within the same temperature range) was -27 ppm / °C. Sample 9 (x = 0.43) had the lowest sulfur content and a smaller cell volume at room temperature compared to other samples.

[0146] Continuous volume shrinkage was observed in the temperature ranges from room temperature to 100°C and from 180°C to 500°C. When calculating the coefficients of thermal expansion for sample 4 (x = 0.90), the volumetric thermal expansion coefficient (30–100°C) was -26 ppm / °C; the volumetric thermal expansion coefficient (180–350°C) was -8.1 ppm / °C; and the volumetric thermal expansion coefficient (350–500°C) was -13 ppm / °C.

[0147] In summary, it has been proven that α-Zr2SP2O 12 The material described exhibits a negative coefficient of thermal expansion in the range of room temperature to 500°C, particularly a very high negative coefficient of thermal expansion in the range of 100-180°C; and the negative coefficient of thermal expansion decreases with decreasing S content. This is due to α-Zr₂SP₂O 12This causes a phase transition from 100°C to 180°C, thus exhibiting a very large negative coefficient of thermal expansion.

[0148] Sample 4 was observed using electron microscopy (FE-SEM). The results were... Figure 7A and Figure 7B As shown in the image. Figure 7A Higher magnification Figure 7B The observation results. For example... Figure 7A and Figure 7B As shown, it was found that the particles in sample 4 were cubic particles with a diameter of 200 to 300 nm on the side, and the particle size distribution was narrow.

[0149] [FE-SEM]

[0150] • Equipment used: JSM-7500F (JEOL)

[0151] Accelerating voltage: 7-10kV

[0152] (Research on hydrothermal treatment conditions)

[0153] The optimal conditions for hydrothermal treatment were investigated. More specifically, samples 10 to 25, shown below, were prepared and evaluated using ICP-OES, XRD, and FE-SEM. In this way, the optimal conditions for hydrothermal treatment were investigated.

[0154] Except for the hydrothermal treatment conditions, the manufacturing methods for samples 10-25 are the same as those for samples 1-9. The equipment used to evaluate the samples is the same as that used to evaluate samples 1-9. The hydrothermal treatment conditions, baking conditions, and atomic ratios of composition for samples 10-25 are shown in the table below. Note that "300°C (drying)" means that the samples were dried at 300°C. Figure 2 (Step S4), and without baking (Step S5). The same applies below.

[0155] [Table 1]

[0156]

[0157] [Table 2]

[0158]

[0159] [Table 3]

[0160]

[0161]

[0162] [Table 4]

[0163]

[0164] Figure 8 XRD measurements for samples 10 to 13 (hydrothermal treatment temperature: 110°C, hydrothermal treatment time: 2 days) are shown. Zr₂SP₂O was observed at any of the baking temperatures of 500°C, 700°C, and 900°C at a hydrothermal treatment temperature of 110°C. 12 XRD peaks of β-Zr2SP2O. 12 (ICDD card: 04-007-8019) It exists as a trace impurity. Furthermore, the α phase differs from the β phase in crystal system and space group. More specifically, the α phase is rhombic and R-3c; while the β phase is orthorhombic and Pbcn-60. The S values ​​in the atomic ratios of the constituent phases are calculated to be 1.1, 0.8, and 0.7, respectively. These values ​​are larger than those of samples subjected to hydrothermal treatment at 180 °C and 130 °C (described later), indicating that S remains compared to samples subjected to hydrothermal treatment under other conditions. This can be attributed to the fact that, due to the formation of the more stable β phase than the α phase, S is difficult to remove even upon heating.

[0165] Figure 9 The XRD results for samples 14 to 17 (hydrothermal treatment temperature: 130°C, hydrothermal treatment time: 2 days) are shown. α-Zr₂SP₂O with satisfactory crystallinity was obtained at a baking temperature of 500°C after hydrothermal treatment at 130°C. 12 A peak in ZrO2 was observed. The atomic ratio of Zr:S was found to be 2:0.8. The S content was slightly lower than the theoretical composition. At baking temperatures of 700℃ and 900℃, α-Zr2SP2O... 12 It coexists with ZrO2; however, the value of S in the atomic ratio decreases to 0.4.

[0166] Figure 10 The XRD results for samples 18-21 (hydrothermal treatment temperature: 180℃, hydrothermal treatment time: 2 days) are shown. Single-phase α-Zr₂SP₂O was manufactured by baking at 500℃ under hydrothermal treatment conditions of 180℃. 12 As for the atomic ratio, Zr:S = 2:0.9 is obtained at a baking temperature of 500°C; while at a baking temperature of 700°C, this atomic ratio decreases to Zr:S = 2:0.5. At a baking temperature of 900°C, the atomic ratio decreases to Zr:S = 2:0.4.

[0167] Samples were prepared by hydrothermal treatment for 0.5 days and 7 days at a hydrothermal temperature of 180°C. As a result, among all samples prepared by hydrothermal treatment for 0.5 to 7 days at a hydrothermal temperature of 180°C, single-phase α-Zr₂SP₂O was produced by baking at 500°C for 4 hours after hydrothermal treatment. 12 Therefore, hydrothermal treatment is performed at a temperature of 180°C for at least 0.5 days, followed by baking. In this way, single-phase α-Zr₂SP₂O can be produced. 12 .

[0168] Figure 11 XRD measurements for samples 22 to 25 (hydrothermal treatment temperature: 230°C, hydrothermal treatment time: 4 days) are shown. Single-phase α-Zr₂SP₂O was manufactured at a baking temperature of 500°C under hydrothermal treatment conditions of 230°C. 12 At a baking temperature of 500°C, the atomic ratio of Zr:S is 2:0.8. In this case, the proportion of S is slightly lower than that of S at a hydrothermal treatment temperature of 180°C; however, no impurity peaks were observed. When baking at 700°C, the atomic ratio decreases to Zr:S = 2:0.5. When baking at 900°C, the atomic ratio decreases to Zr:S = 2:0.4.

[0169] Figure 12 This is a graph showing the relationship between baking temperature and S atomic content for samples treated at different hydrothermal temperatures. (Example) Figure 12 As shown, at a hydrothermal treatment temperature of 110℃, the rate of decrease in S content slows down with increasing baking temperature. Considering... Figure 12 The results showed that, under hydrothermal treatment temperatures above 130℃, the sulfur content in the samples could be controlled to approximately 0.4% by adjusting the baking temperature. This was considered in relation to controlling Zr2SP2O. 12 The composition of the solution, and the hydrothermal treatment temperature is preferably set above 130℃.

[0170] Figure 13A An image of sample 11 (hydrothermal treatment temperature: 110°C) as observed by an electron microscope (FE-SEM) is shown. Figure 13B An image of sample 19 (hydrothermal treatment temperature: 180°C) observed using an electron microscope (FE-SEM) is shown. Figure 13A As shown, in sample 11 (hydrothermal treatment temperature: 110℃), many particles considered to be impurities adhered to α-Zr2SP2O. 12 On the surface of cubic particles. Considering that... Figure 8 β-Zr2SP2O observed in the XRD measurements shown 12The peak indicates that the impurity may be β-Zr2SP2O. 12 Particles. Conversely, such as Figure 13B As shown, in sample 19 treated at a hydrothermal temperature of 180°C, cubic particles of 200-300 nm were observed on the side. No impurities were found on the surface of the cubic particles.

[0171] Considering the above results, in order to control Zr2SP2O 12 The composition, and the preferred hydrothermal treatment temperature is above 130℃. For example... Figure 10 The XRD measurements show that at a hydrothermal treatment temperature of 180℃, single-phase α-Zr2SP2O 12 Manufactured at a baking temperature of 500°C. For the production of single-phase α-Zr₂SP₂O. 12 The preferred hydrothermal treatment temperature is above 180°C. This indicates that if hydrothermal treatment is performed above 180°C, the shape and size of the particles to be manufactured are not affected by the hydrothermal treatment temperature.

[0172] <(2)Zr 2-a Ti a S x P2O 12+δ >

[0173] This section will describe the material (Zr) obtained by replacing some Zr sites with Ti. 2-a Ti a S x P2O 12+δ ). Figure 14 This is a flowchart illustrating a method for manufacturing a material with negative thermal expansion, more specifically a method for manufacturing a material obtained by replacing some Zr sites with element M. Note that in... Figure 14 The same reference numerals used in the flowcharts shown refer to... Figure 2 The steps in the text correspond to the same steps.

[0174] By Zr 2-a Ti a S x P2O 12+δ The negative thermal expansion material is represented by Figure 14The flowchart shown illustrates the manufacturing process. First, prepare the raw materials ZrCl₂O·8H₂O (Wako Premium Grade, Wako Pure Chemical Co., Ltd.), 30% titanium(IV) sulfate solution (chemical grade, Wako Pure Chemical Co., Ltd.), (NH₄)₂HPO₄ (reagent grade, Kanto Chemical Co., Inc.), and H₂SO₄ (reagent grade, Wako Pure Chemical Co., Ltd.). Then, dissolve ZrCl₂O·8H₂O and (NH₄)₂HPO₄ separately in distilled water to 0.8M. Subsequently, mix these aqueous solutions (20 ml each), the 30% titanium(IV) sulfate solution (the amount corresponding to the proportion indicated by "a"), and H₂SO₄ in a volume (ml) of [6 - (the amount of S to be added in the form of titanium sulfate)]. Stir the mixture for 90 minutes using a stirrer (step S1). The 30% titanium(IV) sulfate solution used here corresponds to... Figure 14 The substance shown provides a substitute element.

[0175] After stirring, the resulting aqueous solution (mixture) is poured into a container made of Teflon (registered trademark) (HUT-100, San-Ai Chemical Co., Ltd.), and this container is placed inside an outer cylinder made of pressure-resistant stainless steel (HUS-100, San-Ai Chemical Co., Ltd.). The cylinder is then placed in a hot air circulating oven (KLO-45M, Kwang-Yang Thermal Systems Co., Ltd.) and heated. Hydrothermal treatment (step S2) is performed in this manner. The hydrothermal treatment is carried out at 180°C for 12 days.

[0176] After hydrothermal treatment, the removed Teflon container contained a white precipitate. The solution containing the precipitate was poured into an evaporating dish and heated at approximately 100°C for 5 hours to evaporate excess moisture (Step S3: First Drying Process). At this point, the sample was not completely dried due to the presence of excess H₂SO₄ and residual moisture. Therefore, the evaporating dish containing the sample was placed in an electric furnace (KDF-S80, DENKEN-HIGHDENTAL GmbH) at 300°C and further dried for 12 hours (Step S4: Second Drying Process). Subsequently, the sample dried at 300°C was placed in an electric furnace (KDF-S80, DENKEN-HIGHDENTAL GmbH) and baked at 500°C for 4 hours. In this manner, a white powder sample was obtained (Step S5).

[0177] To determine the crystal structure of the sample thus manufactured, X-ray diffraction measurements were performed. Figure 15 This illustrates a material (Zr) obtained by replacing some Zr sites with Ti. 2-a Ti a S x P2O 12+δThe XRD measurement results are shown below. Note that the equipment and conditions used for the XRD measurements are the same as described above.

[0178] exist Figure 15 In the XRD measurement results shown, the XRD pattern of the sample with a=0 is similar to that of α-Zr2SP2O. 12 The XRD patterns of the crystalline phases (ICDD card number: 04-017-0937) are almost identical. In samples with a = 0.8 to 1.8, except for α-Zr₂SP₂O… 12 Furthermore, impurity phases were identified, and their peaks were broad. Conversely, in samples with a = 0.1 to 0.7, no impurity phases were identified; only α-Zr₂SP₂O was confirmed. 12 The crystal phase. Therefore, in samples with a value of 0 < a ≤ 0.7, it is considered that some Zr sites were successfully substituted by Ti.

[0179] The atomic ratios of samples (a = 0.1 to 0.7) obtained by substituting some Zr sites with Ti were determined using an ICP-OES instrument. Figure 16 This shows the Zr used in practice. 2-a Ti a SP2O 12 The table shows the composition of the data. Note that the equipment and conditions used for XRD measurements are the same as described above.

[0180] like Figure 16 As shown, the ratio of Zr to Ti is normalized by the concentration of S. Based on the above results, the concentration of S is normalized by setting x = 0.9. Figure 16 As shown, Ti was confirmed to be present in approximately stoichiometric proportions. This indicates that, although the Zr content is slightly lower, the element is present in approximately stoichiometric proportions in the sample except for a = 0.1. The low Zr content in the sample with a = 0.1 is considered to be due to only Zr not being fully dissolved when the sample was dissolved in the mixed acid.

[0181] The cell volume (coefficient of thermal expansion) of the sample obtained by replacing some Zr sites with Ti was obtained using a high-temperature XRD instrument. Figure 17 It shows the manufactured Zr 2-a Ti a SP2O 12 A graph showing the temperature characteristics (temperature dependence of cell volume). Note that the equipment and conditions used for high-temperature XRD measurements are the same as described above.

[0182] like Figure 17 As shown, in Zr 2-a Ti a SP2O 12 In all samples (a = 0.1 to 0.7), Zr2SP2O 12Compared to the unit cell volume of (a=0), Zr 2-a Ti a SP2O 12 The cell volumes of all samples with a = 0.1 to 0.7 are small. The trend is that the cell volume decreases with increasing Ti content. The ionic radius of the tetravalent hexacoordinate Zr ion is... The ionic radius of the tetravalent hexacoordinate Ti ion is... Therefore, the reason why the cell volume decreases with the increase of Ti content is believed to be that some Zr sites are replaced by Ti with ionic radii smaller than Zr ionic radii.

[0183] Samples with a = 0.1 to 0.4 were found to exhibit a three-step thermal expansion behavior, similar to Zr₂SP₂O. 12 (a=0). Therefore, it is assumed that whenever the slope of the unit cell volume changes, a negative coefficient of thermal expansion is exhibited due to the structure-phase transition-framework. For example... Figure 17 As shown, in Zr2SP2O with a = 0.1 to 0.4 12 In the samples, the temperature range showing volume shrinkage due to phase transition tends to be greater than that of Zr2SP2O when a=0. 12 It needs to be big.

[0184] Conversely, in samples with a = 0.5 to 0.7, the volume shrinkage of the portion causing the phase transition was significantly reduced. Compared to samples with a = 0.1 to 0.4, the cell volume at the start of the measurement (low-temperature side) was significantly reduced. In the sample with a = 0.7, considering the change in cell volume, virtually no volume shrinkage due to the phase transition was identified. Therefore, it is believed that the conditions for samples with a = 0.1 to 0.4 may be significantly different from those for samples with a = 0.5 to 0.7.

[0185] The lattice constant at room temperature varies with the Ti content. However, in all samples at 773 K, it was confirmed that the cell volume decreases at regular intervals with increasing Ti content. The relationship between Ti content and cell volume is... Figure 18 As shown in the image. Figure 18 As shown, the decrease in Ti content and cell volume has a linear relationship, confirming that they follow Vigarde's law.

[0186] Regarding Zr 2-a Ti a SP2O 12+δ For samples with a = 0.1 to 0.7, the temperature dependence of the lattice constants along the a-axis and c-axis was investigated. The results showed that, in all samples, the change in the lattice constant along the c-axis was greater than that along the a-axis. These results are consistent with those of α-Zr₂SP₂O. 12The results are the same as those above (see Figure 1).

[0187] Figure 19 This section focuses on samples obtained by replacing some Zr sites with Ti (Zr 2-a Ti a SP2O 12 A graph showing the coefficient of thermal expansion (a = 0.1 to 0.7) over various temperature ranges. Figure 19 In this context, ZSP represents the sample where a = 0. For example... Figure 19 As shown, Zr was found 2-a Ti a SP2O 12+δ The coefficient of thermal expansion (a = 0.1 to 0.7) varies over different temperature ranges. In the negative thermal expansion material according to the invention, since the coefficient of thermal expansion varies depending on the composition of Ti, the composition of the material can be appropriately selected according to the intended use.

[0188] <(3)Zr 2-a Ce a S x P2O 12+δ >

[0189] This section will describe the material obtained by replacing some Zr sites with Ce (Zr 2-a Ce a S x P2O 12+δ ).

[0190] By Zr 2-a Ce a S x P2O 12+δ The negative thermal expansion material is also based on Figure 14 The flowchart shown illustrates the manufacturing process. First, prepare the raw materials ZrCl₂O·8H₂O (Wako Premium Grade, Wako Pure Chemical Co., Ltd.), cerium sulfate tetrahydrate (Wako Premium Grade, Wako Pure Chemical Co., Ltd.), NH₄H₂PO₄ (Reagent Premium Grade, Wako Pure Chemical Co., Ltd.), and H₂SO₄ (Reagent Premium Grade, Wako Pure Chemical Co., Ltd.). Then, dissolve ZrCl₂O·8H₂O and (NH₄)₂HPO₄ separately in distilled water to 0.8M. Subsequently, mix these aqueous solutions (10 ml each), cerium sulfate tetrahydrate (the amount corresponding to the proportion indicated by "a"), and H₂SO₄ (3 ml). Stir the mixture with a stirrer for 90 minutes (step S1). The cerium sulfate tetrahydrate used here corresponds to... Figure 14 The substance shown is derived from the substituted element. Note that the following steps of this method are different from those used for Zr. 2-a Ti a S x P2O 12+δThe steps for manufacturing the negative thermal expansion material are the same, and for the sake of brevity, no further explanation is omitted.

[0191] To determine the crystal structure of the sample thus prepared, X-ray diffraction measurements were performed. Figure 20 The material obtained by replacing some Zr sites with Ce is shown (Zr 2-a Ce a S x P2O 12+δ The XRD measurement results are shown below. Note that the equipment and conditions used for the XRD measurements are the same as described above.

[0192] exist Figure 20 The XRD measurements shown confirm α-Zr₂SP₂O in samples with α = 0.2 to 0.6 (Ce 0.2–0.6). 12 The (α-ZSP) crystal phase was observed. Conversely, the ZrP₂O₇ crystal phase was confirmed in samples with a Ce content of a = 0.6 or higher. Therefore, in samples with a value of 0 < a ≤ 0.4, it is believed that some Zr sites were successfully substituted by Ce.

[0193] The unit cell volume (coefficient of thermal expansion) of the sample obtained by replacing some Zr sites with Ce was obtained using a high-temperature XRD instrument. Figure 21 This shows the prepared Zr 2-a Ce a SP2O 12 A graph showing the temperature characteristics (temperature dependence of cell volume). Note that the equipment and conditions used for high-temperature XRD measurements are the same as described above.

[0194] like Figure 21 As shown, in Zr 2-a Ce a SP2O 12 In the sample with (a=0.4), Zr2SP2O 12 Compared to the unit cell volume of (ZSP), Zr 2-a Ce a SP2O 12 The sample with a = 0.4 has a large cell volume. The temperature dependence of the cell volume is shown in the relationship with that in Zr₂SP₂O. 12 The same behavior was observed in (ZSP). More specifically, Zr was found to exhibit the same behavior. 2-a Ce a SP2O 12 (a=0.4) exhibits similar behavior to Zr2SP2O 12 The three-step thermal expansion behavior of (ZSP) is observed. Therefore, it is assumed that whenever the slope of the cell volume changes, a negative thermal expansion coefficient is exhibited due to the structure-phase transition-structure.

[0195] <(4)Zr 2-a Mn a S x P2O 12+δ >

[0196] This section will describe the material obtained by replacing some Zr sites with Mn (Zr 2-a Mn a S x P2O 12+δ ).

[0197] By Zr 2-a Mn a S x P2O 12+δ The negative thermal expansion material is also based on Figure 14 The process is as shown in the flowchart. First, prepare the raw materials ZrCl2O·8H2O (Wako Premium Grade, Wako Pure Chemical Co., Ltd.), manganese dioxide (MnO2) (Reagent Premium Grade, KOKUSAN CHEMICAL CO.,LTD.), (NH4)2HPO4 (Reagent Premium Grade, Kanto Chemical Co., Ltd.), and H2SO4 (Reagent Premium Grade, Wako Pure Chemical Industry Co., Ltd.). Then, dissolve ZrCl2O·8H2O and (NH4)2HPO4 separately in distilled water to 0.8M. Subsequently, mix these aqueous solutions (10 ml each), manganese dioxide (MnO2) (the amount corresponding to the proportion indicated by "a"), and H2SO4 (3 ml). Stir the mixture with a stirrer for 90 minutes (step S1). The manganese dioxide (MnO2) used here corresponds to... Figure 14 The substance shown is derived from the substituted element. Note that the following steps of this method are different from those used for Zr. 2-a Ti a S x P2O 12+δ The steps for manufacturing the negative thermal expansion material are the same, and for the sake of brevity, no further explanation is omitted.

[0198] To determine the crystal structure of the sample thus prepared, X-ray diffraction measurements were performed. Figure 22 The material obtained by replacing some Zr sites with Mn is shown (Zr 2-a Mn a S x P2O 12+δ The XRD measurement results are shown below. Note that the equipment and conditions used for the XRD measurements are the same as described above.

[0199] exist Figure 22The XRD measurements shown confirm α-Zr₂SP₂O in samples with a = 0.1 to 0.4 (Mn 0.1 to 0.4). 12 The (α-ZSP) crystal phase was observed. Conversely, in samples with Mn content a = 0.3 or higher, impurity phases (indicated by arrows) were confirmed. Therefore, in samples with a = 0 < a ≤ 0.2, it is believed that some Zr sites were successfully substituted by Mn.

[0200] The unit cell volume (coefficient of thermal expansion) of the sample obtained by replacing some Zr sites with Mn was obtained using a high-temperature XRD instrument. Figure 23 This shows the prepared Zr 2-a Mn a SP2O 12 A graph showing the temperature characteristics (temperature dependence of cell volume). Note that the equipment and conditions used for high-temperature XRD measurements are the same as described above.

[0201] like Figure 23 As shown, in Zr 2-a Mn a SP2O 12 In the samples with (a = 0.1, a = 0.2), the unit cell volume is almost equal to that of Zr2SP2O. 12 The cell volume of (ZSP) is shown. The temperature dependence of the cell volume is illustrated with respect to the temperature of Zr₂SP₂O. 12 The same behavior was observed in (ZSP). More specifically, Zr was found to exhibit the same behavior. 2-a Mn a SP2O 12 (a = 0.1, a = 0.2) exhibits similar behavior to Zr2SP2O 12 The three-step thermal expansion behavior of (ZSP) is observed. Therefore, it is assumed that whenever the slope of the cell volume changes, a negative thermal expansion coefficient is exhibited due to the structure-phase transition-structure.

[0202] <(5)Zr 2-a Sn a S x P2O 12+δ >

[0203] This section will describe the material (Zr) obtained by replacing some Zr sites with Sn. 2-a Sn a S x P2O 12+δ ).

[0204] By Zr 2-a Sn a S x P2O 12+δ The negative thermal expansion material is also based on Figure 14The flowchart shown illustrates the manufacturing process. First, prepare the raw materials ZrCl2O·8H2O (Wako Premium Grade, Wako Pure Chemical Co., Ltd.), tin oxide (SnO2) (Premium Grade based on manufacturer's standards, Kanto Chemical Co., Ltd.), (NH4)2HPO4 (Reagent Premium Grade, Kanto Chemical Co., Ltd.), and H2SO4 (Reagent Premium Grade, Wako Pure Chemical Co., Ltd.). Then, dissolve ZrCl2O·8H2O and (NH4)2HPO4 separately in distilled water to 0.8M. Subsequently, mix these aqueous solutions (10 ml each), tin oxide (SnO2) (the amount corresponding to the proportion indicated by "a"), and H2SO4 (3 ml). Stir the mixture with a stirrer for 90 minutes (step S1). The tin oxide (SnO2) used here corresponds to... Figure 14 The substance shown is derived from the substituted element. Note that the following steps of this method are different from those used for Zr. 2-a Ti a S x P2O 12+δ The steps for manufacturing the negative thermal expansion material are the same, and for the sake of brevity, no further explanation is omitted.

[0205] To determine the crystal structure of the sample thus prepared, X-ray diffraction measurements were performed. Figure 24 The material obtained by replacing some Zr sites with Sn is shown. 2-a Sn a S x P2O 12+δ The XRD measurement results are shown below. Note that the equipment and conditions used for the XRD measurements are the same as described above.

[0206] exist Figure 24 The XRD measurements shown confirm α-Zr₂SP₂O in samples with a = 0.2 to 0.8 (Sn 0.2–0.8). 12 The (α-ZSP) crystalline phase was observed. Conversely, impurity phases were identified in samples with Sn content a = 1.0 or higher. Therefore, in samples with a = 0 < a ≤ 0.8, it is believed that some Zr sites were successfully substituted by Sn.

[0207] The unit cell volume (coefficient of thermal expansion) of the sample obtained by replacing some Zr sites with Sn was obtained using a high-temperature XRD instrument. Figure 25 This shows the prepared Zr 2-a Sn a SP2O 12 A graph showing the temperature characteristics (temperature dependence of cell volume). Note that the equipment and conditions used for high-temperature XRD measurements are the same as described above.

[0208] like Figure 25 As shown, in Zr2-a Sn a SP2O 12 In samples with a = 0.4 and a = 0.6, the interaction with Zr2SP2O 12 Compared to the unit cell volume of Zr at 300-400 (K), Zr 2-a Sn a SP2O 12 The samples with a = 0.4 and a = 0.6 have large unit volumes. The temperature dependence of the unit volume is shown in the relationship with that in Zr₂SP₂O. 12 The same behavior in (ZSP). In Zr 2-a Sn a SP2O 12 In (a=0.2), the unit cell volume of the sample is almost equal to that of Zr2SP2O. 12 The unit cell volume of (ZSP). More specifically, Zr was found to be... 2-a Sn a SP2O 12 (a = 0.2 to 0.6) exhibits similarity to Zr2SP2O 12 The three-step thermal expansion behavior of (ZSP) is observed. Therefore, it is assumed that whenever the slope of the cell volume changes, a negative thermal expansion coefficient is exhibited due to the structure-phase transition-structure.

[0209] Figure 26 This is a graph showing the coefficients of thermal expansion of samples obtained by replacing some Zr sites with Ce, Mn, and Sn at different temperature ranges. Figure 2 As shown, negative coefficients of thermal expansion were also observed in samples obtained by replacing some Zr sites with Ce, Mn, and Sn. Furthermore, the coefficients of thermal expansion varied across different temperature ranges. Therefore, materials with different coefficients of thermal expansion can be formed by replacing some Zr sites with these elements. Thus, the elements used for substitution can be appropriately selected based on, for example, the intended use.

[0210] <(6)Zr2S 1-b Mo b P2O 12+δ >

[0211] This section will describe the material (Zr) obtained by replacing some S sites with Mo. 2-a Sn a S x P2O 12+δ ). By Zr2S 1- b Mo b P2O 12+δ The negative thermal expansion material is manufactured through two processes, namely Figure 14 The flowchart shows process A and Figure 27 Process B is shown in the flowchart.

[0212] (Process A)

[0213] First, process A will be described. For example... Figure 14 As shown, the raw materials prepared are ZrCl2O·8H2O (Wako Special Grade, Wako Pure Chemical Co., Ltd.) and (NH4)6Mo7O. 24 • ZrCl₂O aqueous solution (Wako Premium Grade, Wako Pure Chemical Co., Ltd.), (NH₄)₂HPO₄ (Reagent Premium Grade, Kanto Chemical Co., Ltd.), and H₂SO₄ (Reagent Premium Grade, Wako Pure Chemical Co., Ltd.). Then, ZrCl₂O·8H₂O and (NH₄)₂HPO₄ were each dissolved in distilled water to a final concentration of 0.8 M. Subsequently, these aqueous solutions (10 ml each), (NH₄)₆Mo₇O₇, and ZrCl₂O₄ were dissolved in distilled water to a final concentration of 0.8 M. 24 • Mix 4H₂O aqueous solution (the amount corresponding to the proportion indicated by "b") and 3 ml of H₂SO₄. Stir the mixture with a stirrer for 90 minutes (step S1). The (NH₄)₆Mo₇O used here... 24 · 4H2O aqueous solution corresponds to Figure 14 The substance shown is derived from the substituted element. The steps of this method are the same as those of other methods described above for manufacturing materials with negative thermal expansion. Note that in... Figure 14 In the baking step shown (step S5), two samples were prepared: a sample baked at 500°C for 4 hours and a sample baked at 800°C for 4 hours.

[0214] (Process B)

[0215] Describe process B. Note that in Figure 27 In the flowchart shown, steps S1 to S5 are... Figure 14 The flowcharts shown are basically the same.

[0216] like Figure 27 As shown, first, prepare the raw materials ZrCl₂O·8H₂O (Wako Premium Grade, Wako Pure Chemical Co., Ltd.), (NH₄)₂HPO₄ (Reagent Premium Grade, Kanto Chemical Co., Ltd.), and H₂SO₄ (Reagent Premium Grade, Wako Pure Chemical Co., Ltd.). Then, dissolve ZrCl₂O·8H₂O and (NH₄)₂HPO₄ separately in distilled water to a concentration of 0.8 M. Subsequently, mix these aqueous solutions (10 ml each) with 3 ml of H₂SO₄. Stir the mixture for 90 minutes using a stirrer (step S1). Steps S2 to S5 are performed in conjunction with... Figure 14 The manufacturing method shown is the same. Note that in the baking step (step S5), two samples were prepared: a sample baked at 600°C for 4 hours and a sample baked at 800°C for 4 hours.

[0217] After that, (NH4)6Mo7O 24 • 4H2O aqueous solution (Wako Special Grade, Wako Pure Chemical Co., Ltd.) is used with the Zr2SP2O prepared in step S5 12+δ The powder is impregnated (step S6). Then, the mixture containing Zr2SP2O is filtered. 12+δ Powder and (NH4)6Mo7O 24 • A solution of 4H2O aqueous solution (step S7). Then, the filtrate (powder) is baked at 500°C for 4 hours to prepare the sample (step S8).

[0218] To determine the crystal structure of the sample thus prepared, X-ray diffraction measurements were performed. Figure 28 The preparation of Zr2S according to process A is shown. 1-b Mo b P2O 12+δ The XRD measurement results for the material are shown. Note that the equipment and conditions used for the XRD measurements are the same as described above.

[0219] Figure 28 The XRD results of the following samples are shown: (Mo content: b = 0.2, baking temperature of step S5: 500℃ (b = 0.2-500)), (Mo content: b = 0.2, baking temperature of step S5: 800℃ (b = 0.2-800)), (Mo content: b = 0.6, baking temperature of step S5: 500℃ (b = 0.6-500)), and (Mo content: b = 0.6, baking temperature of step S5: 800℃ (b = 0.6-800)).

[0220] exist Figure 28 The XRD results shown confirm α-Zr₂SP₂O in samples with Mo content b = 0.2 and baking temperature of 500°C in step S5 (b = 0.2-500) and samples with Mo content b = 0.6 and baking temperature of 500°C in step S5 (b = 0.6-500). 12 (α-ZSP) crystal phase. Therefore, under these conditions, it is believed that some S sites were successfully substituted by Mo.

[0221] Conversely, in samples with Mo content b = 0.2 and baking temperature of step S5: 800°C (b = 0.2-800), and samples with Mo content b = 0.6 and baking temperature of step S5: 800°C (b = 0.6-800), ZrO2 peaks were confirmed in addition to the α-ZSP phase peaks. Therefore, if the baking temperature of step S5 is high (800°C), the presence of ZrO2 is confirmed.

[0222] Figure 29The material (Zr2S) prepared according to process B is shown. 1-b Mo b P2O 12+δ XRD measurement results of ). Figure 29 The XRD measurement results for the sample (baking temperature in step S5: 600℃, Mo content: b = 0.02) are shown in the top figure (top figure) and the XRD measurement results for the sample (baking temperature in step S5: 800℃, Mo content: b = 0.02) are shown in the bottom figure (bottom figure). Note that the equipment and conditions used for high-temperature XRD measurements are the same as described above.

[0223] exist Figure 29 The XRD measurements shown in the above figure (Mo_600) confirm several peaks of the β-ZSP phase in addition to the peaks of the α-ZSP phase. Figure 29 In the XRD measurements shown in the figure below (Mo_800), several ZrO2 peaks were confirmed in addition to the α-ZSP phase peaks. β-ZSP and ZrO2 peaks also appeared; however, these peaks were of lower intensity. Since the α-ZSP phase peaks preferentially appeared, it is considered that some S sites were successfully substituted by Mo under these conditions.

[0224] The cell volume (coefficient of thermal expansion) of the sample obtained by replacing some S sites with Mo was obtained by using a high-temperature XRD apparatus. Figure 30 and Figure 31 This shows the prepared Zr2S 1-b Mo b P2O 12 A graph showing the temperature characteristics (temperature dependence of cell volume). Note that the equipment and conditions used for high-temperature XRD measurements are the same as described above.

[0225] Figure 30 It shows in Figure 14 Zr2SP2O obtained by baking at 500°C in step S5 12 (ZSP)(ZSP_500℃) and ZSP(ZSP_600℃) obtained by baking at 600℃, and in Figure 27 The Zr2S obtained in step S5 by baking at a temperature of 600°C 1-b Mo b P2O 12 Temperature characteristics of (Mo_600℃). Figure 31 It shows in Figure 14 In step S5, the ZSP obtained by baking at 700°C (ZSP_700°C) and the ZSP obtained by baking at 900°C (ZSP_900°C), and in Figure 27 The Zr2S obtained in step S5 by baking at a temperature of 800°C1-b Mo b P2O 12 Temperature characteristics of (Mo_800℃).

[0226] like Figure 30 As shown, Zr2S was obtained by baking at 600°C. 1-b Mo b P2O 12 In (Mo_600℃), the cell volume of the sample at 300-400(K) is smaller than that of ZSP. The temperature dependence of the cell volume shows the same behavior as in ZSP. Figure 31 As shown, Zr2S was obtained by baking at 800°C. 1- b Mo b P2O 12 In (Mo_800℃), the cell volume of the sample at 300-400(K) is smaller compared to that of the ZSP_700℃ sample. For example... Figure 31 As shown, Zr2S was obtained by baking at 800°C. 1-b Mo b P2O 12 In (Mo_800℃), the same temperature dependence was observed in the 300-800(K) range as in ZSP_900℃. Therefore, the Zr2S obtained by replacing some S sites with Mo was confirmed. 1-b W b P2O 12 It exhibits a negative coefficient of thermal expansion.

[0227] <(7)Zr2S 1-b W b P2O 12+δ >

[0228] This section will describe the material (Zr2S) obtained by replacing some S sites with W. 1-b W b P2O 12+δ ). By Zr2S 1- b W b P2O 12+δ The negative thermal expansion material is prepared through two processes, namely Figure 14 The flowchart shows process A and Figure 27 Process B is shown in the flowchart.

[0229] (Process A)

[0230] First, process A will be described. For example... Figure 14As shown, the raw materials prepared are ZrCl2O·8H2O (Wako Special Grade, Wako Pure Chemical Co., Ltd.) and NH4. 10 W 12 O 41 ZrCl₂O·8H₂O (Wako Pure Chemicals Co., Ltd.), (NH₄)₂HPO₄ (premium grade reagent, Kanto Chemical Co., Ltd.), and H₂SO₄ (premium grade reagent, Wako Pure Chemicals Co., Ltd.) were prepared. Then, ZrCl₂O·8H₂O and (NH₄)₂HPO₄ were dissolved separately in distilled water to a final concentration of 0.8 M. Subsequently, these aqueous solutions (10 ml each), (NH₄)₂O·8H₂O·8HPO₄ ... 10 W 12 O 41 Mix 5 ml of H₂O (the amount corresponding to the proportion indicated by "b") and 3 ml of H₂SO₄. Stir the mixture for 90 minutes using a stirrer (step S1). The (NH₄) used here... 10 W 12 O 41 ·5H2O corresponds to Figure 14 The substance shown is derived from the substituted element. The steps of this method are the same as those of other methods described above for manufacturing negative thermal expansion materials. Note that in the baking step (step S5), two samples are prepared: a sample baked at 500°C for 4 hours and a sample baked at 800°C for 4 hours.

[0231] (Process B)

[0232] Describe process B. Note that in Figure 27 In the flowchart shown, steps S1 to S5 are... Figure 14 Steps S1 to S5 in the flowchart shown are basically the same.

[0233] like Figure 27 As shown, first, prepare the raw materials ZrCl₂O·8H₂O (Wako Premium Grade, Wako Pure Chemical Co., Ltd.), (NH₄)₂HPO₄ (Reagent Premium Grade, Kanto Chemical Co., Ltd.), and H₂SO₄ (Reagent Premium Grade, Wako Pure Chemical Co., Ltd.). Then, dissolve ZrCl₂O·8H₂O and (NH₄)₂HPO₄ separately in distilled water to a concentration of 0.8 M. Subsequently, mix these aqueous solutions (10 ml each) with 3 ml of H₂SO₄. Stir the mixture for 90 minutes using a stirrer (step S1). Steps S2 to S5 are performed in conjunction with... Figure 14 The manufacturing method shown is the same. Note that in the baking step (step S5), two samples were prepared: a sample baked at 600°C for 4 hours and a sample baked at 800°C for 4 hours.

[0234] After that, (NH4) 10 W 12 O41 • 5H2O aqueous solution (Wako Special Grade, Wako Pure Chemical Co., Ltd.) is used with the Zr2SP2O prepared in step S5 12+δ Powder impregnation (step S6). Then, filter containing Zr2SP2O. 12+δ Powder and (NH4) 10 W 12 O 41 A solution of 5H2O was prepared (step S7). The filtrate (powder) was then baked at 500°C for 4 hours to prepare the sample (step S8).

[0235] To determine the crystal structure of the sample thus prepared, X-ray diffraction measurements were performed. Figure 32 The material (Zr2S) prepared according to process A is shown. 1-b Wo b P2O 12+δ The XRD measurement results are shown below. Note that the equipment and conditions used for the XRD measurements are the same as described above.

[0236] Figure 32 The XRD results of the following samples are shown: (W content: b = 0.2, baking temperature of step S5: 500℃ (b = 0.2-500)), (W content: b = 0.2, baking temperature of step S5: 800℃ (b = 0.2-800)), (W content: b = 0.6, baking temperature of step S5: 500℃ (b = 0.6-500)), and (W content: b = 0.6, baking temperature of step S5: 800℃ (b = 0.6-800)).

[0237] exist Figure 32 The XRD measurements shown confirmed the presence of the α-ZSP phase in samples with a W content of b = 0.2 and a baking temperature of 500°C in step S5 (b = 0.2-500). Therefore, under these conditions, it is considered that some S sites were successfully substituted by W.

[0238] Conversely, in the samples with W content: b = 0.2 and baking temperature of step S5: 800°C (b = 0.2-800), the samples with W content: b = 0.6 and baking temperature of step S5: 500°C (b = 0.6-500), and the samples with W content: b = 0.6 and baking temperature of step S5: 800°C (b = 0.6-800), in addition to the peaks of the α-ZSP crystal phase, peaks of the impurity phase were also confirmed (indicated by arrows).

[0239] Figure 33 The material (Zr2S) prepared according to process B is shown. 1-b W b P2O 12+δ XRD measurement results of ). Figure 33 The XRD measurement results for the sample (baking temperature in step S5: 600℃, W content: b = 0.06) are shown in the upper figure (top figure) and the XRD measurement results for the sample (baking temperature in step S5: 800℃, W content: b = 0.06) are shown in the lower figure (bottom figure). Note that the equipment and conditions used for high-temperature XRD measurements are the same as described above.

[0240] exist Figure 33 In the XRD measurement results shown in the above figure (W_600), in addition to the peaks of the α-ZSP phase, several peaks of the β-ZSP phase were also confirmed. Figure 33 In the XRD measurements shown in Figure (W_800), several ZrO2 peaks were confirmed in addition to the α-ZSP phase peaks. β-ZSP and ZrO2 peaks also appeared; however, these peaks were of lower intensity. Since the α-ZSP phase peaks preferentially appeared, it is considered that some S sites were successfully substituted by W under these conditions.

[0241] The cell volume (thermal expansion coefficient) of the sample obtained by replacing some S sites with W was obtained by using a high-temperature XRD instrument. Figure 34 and Figure 35 This shows the prepared Zr2S 1-b W b P2O 12 A graph showing the temperature characteristics (temperature dependence of cell volume). Note that the equipment and conditions used for high-temperature XRD measurements are the same as described above.

[0242] Figure 3 It shows in Figure 14 In step S5, the ZSP obtained by baking at 500°C (ZSP_500°C) and the ZSP obtained by baking at 600°C (ZSP_600°C), and in Figure 27 The Zr2S obtained in step S5 by baking at a temperature of 600°C 1-b W b P2O 12 Temperature characteristics (W_600℃). Figure 35 It shows in Figure 14 In step S5, the ZSP obtained by baking at 700°C (ZSP_700°C) and the ZSP obtained by baking at 900°C (ZSP_900°C), and in Figure 27 The Zr2S obtained in step S5 by baking at a temperature of 800°C 1-b W b P2O 12 Temperature characteristics (W_800℃).

[0243] like Figure 34As shown, Zr2S was obtained by baking at 600°C. 1-b W b P2O 12 At (W_600℃), the cell volume of the sample is smaller in the 300-400(K) range compared to that of ZSP. The temperature dependence of the cell volume shows the same behavior as ZSP. (See figure). Figure 35 As shown, Zr2S was obtained by baking at 800°C. 1-b W b P2O 12 In (W_800℃), the cell volume of the sample at 300-400(K) is smaller compared to that at ZSP_700℃. For example... Figure 31 As shown, Zr2S was obtained by baking at 800°C. 1-b W b P2O 12 In (W_800℃), the same temperature dependence as ZSP_900℃ was observed in the range of 300-800(K). Therefore, the Zr2S obtained by replacing part of the S sites with W was confirmed. 1- b W b P2O 12 It exhibits a negative coefficient of thermal expansion.

[0244] The above describes the Zr obtained by substituting some Zr sites. 2-a M a S x P2O 12+δ Examples of the present invention include those obtained by replacing a portion of the S site. However, in this invention, both the Zr site and the S site can be replaced.

[0245] The present invention has been described above in conjunction with embodiments. The present invention is not limited to the construction of the above embodiments, and undoubtedly includes various modifications, corrections, and combinations that can be made by those skilled in the art within the scope of the claims of this application.

Claims

1. A negative thermal expansion material, said negative thermal expansion material having a negative coefficient of thermal expansion in the range of room temperature to 500°C, and composed of Zr 2-a M a S x P2O 12+δ It means that, among them, M is at least one selected from the group consisting of Ti, Ce, Sn, Mn, Hf, Ir, Pb, Pd, and Cr; a is 0 < a < 2; x is 0.48 < x < 0.9; and δ is a value defined to satisfy a charge neutrality condition, Zr 2-a M a S x P2O 12+δ the crystal phase of P2O6is an α phase, and Zr 2-a M a S x P2O 12+δ the space group of P2O6is R-3c.

2. The negative thermal expansion material according to claim 1, wherein, a=0, the negative thermal expansion material is Zr2S x P2O 12+δ express.

3. The negative thermal expansion material according to claim 1, wherein, M is Ti, and a is 0 < a ≤ 0.

7.

4. The negative thermal expansion material according to claim 1, wherein, M is Ce, and a is 0 < a ≤ 0.

4.

5. The negative thermal expansion material according to claim 1, wherein, M is Sn, and a is 0 < a ≤ 1.

6. The negative thermal expansion material according to claim 1, wherein, M is Mn, and a is 0 < a ≤ 0.

2.

7. The negative thermal expansion material according to any one of claims 1 to 6, wherein, Some S bits are replaced by Mo or W.

8. The negative thermal expansion material according to claim 1, wherein, The absolute value of the volume expansion coefficient of the negative thermal expansion material at temperatures between 100 and 180°C is greater than the absolute value of the volume expansion coefficient of the negative thermal expansion material at temperatures greater than 180°C.

9. A composite material comprising a negative thermal expansion material according to any one of claims 1 to 8, and a material having a positive thermal expansion coefficient.

10. A composite material comprising a negative thermal expansion material according to claim 7 or 8, and a resin material having a positive thermal expansion coefficient.

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