Negative thermal expansion material, manufacturing method thereof and composite material

Abstract

Provided is a negative thermal expansion material having excellent negative thermal expansion properties and exhibiting a moderately reduced volume as a result of a temperature increase compared to a conventional zinc-phosphorus composite oxide such as Zn2P2O7. The negative thermal expansion material according to the present invention is a composite of a zinc-phosphorus composite oxide represented by general formula (1) ZnxMyPz1Ot1 (1) and a pyrophosphoric acid metal salt represented by general formula (2) AwPz2Ot2 (2), and is characterized in that the composite preferably has a core-shell structure in which the core contains the zinc-phosphorus composite oxide represented by general formula (1) and the shell contains the pyrophosphoric acid metal salt represented by general formula (2).

Description

Technical Field

[0001] This invention relates to a negative thermal expansion material that contracts upon temperature rise, a method for manufacturing the same, and a composite material containing the negative thermal expansion material. Background Technology

[0002] Most substances increase in length and volume due to thermal expansion when the temperature rises. In contrast, there are also known materials that decrease in volume when heated, exhibiting negative thermal expansion (hereafter sometimes referred to as "negative thermal expansion materials").

[0003] It is known that materials exhibiting negative thermal expansion, when used in conjunction with other materials, can suppress changes in the thermal expansion of the materials caused by temperature variations.

[0004] Materials exhibiting negative thermal expansion include, for example, β-lithium nepheline, zirconium tungstate (ZrW₂O₈), zirconium phosphotungstate (Zr₂WO₄(PO₄)₂), and Zn. x Cd 1-x (CN)2, manganese nitrides, bismuth-nickel-iron oxides, etc.

[0005] Zirconium phosphotungstenate is known to have a linear expansion coefficient of -3.4 to -3.0 ppm / ℃ in the temperature range of 0–400℃, exhibiting significant negative thermal expansion. By combining this zirconium phosphotungstenate with materials exhibiting positive thermal expansion (hereinafter sometimes referred to as "positive thermal expansion materials"), materials with low thermal expansion can be manufactured (see Patent Documents 1–2, etc.). Furthermore, a scheme has been proposed that combines a polymer compound such as a resin, which is a positive thermal expansion material, with a negative thermal expansion material (see Patent Document 3, etc.).

[0006] In addition, Patent Document 3 proposes a negative thermal expansion material, wherein the zinc-phosphorus composite oxide of Zn2P2O7 and a portion of the Zn in the zinc-phosphorus composite oxide are selected from at least one element selected from Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, La, Ta, W, Bi, or a portion of P is selected from at least one substitution of Al, Si, V, Ge, Sn.

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2005-35840 Patent Document 2: Japanese Patent Application Publication No. 2015-10006 Patent Document 3: International Publication No. 2022 / 114004 Summary of the Invention

[0008] The problem that the invention aims to solve The zinc-phosphorus composite oxide of Zn2P2O7 and zinc partially replaced by other metals in Patent Document 3 has the following advantages: it has a smaller coefficient of linear expansion compared to zirconium phosphotungstenate, can be manufactured with cheaper raw material systems, can be industrially advantageously manufactured, and has excellent water resistance.

[0009] However, zinc-phosphorus composite oxides such as Zn₂P₂O₇ exhibit a sharp volume reduction with increasing temperature. For example, Zn₂P₂O₇ shows a sharp volume reduction with increasing temperature in the range of 100–150 °C. Therefore, in composite materials containing both negative and positive thermal expansion materials, the positive thermal expansion material cannot keep up with the sharp volume reduction of the negative thermal expansion material. Consequently, it is difficult to achieve zero or low thermal expansion rates in composite materials containing negative thermal expansion materials.

[0010] Therefore, the object of the present invention is to provide a negative thermal expansion material that has excellent negative thermal expansion properties and exhibits a gradual volume reduction with increasing temperature compared to existing zinc-phosphorus composite oxides such as Zn2P2O7.

[0011] Technical solutions for solving the problem In the process of researching methods to improve various negative thermal expansion properties of zinc-phosphorus composite oxides such as Zn2P2O7, the inventors of this invention discovered that the composite of this zinc-phosphorus composite oxide with a specific metal pyrophosphate salt has excellent negative thermal expansion properties, and compared with existing zinc-phosphorus composite oxides such as Zn2P2O7, it becomes a negative thermal expansion material that shows a gradual reduction in volume with increasing temperature, thus completing this invention.

[0012] That is, the present invention (1) provides a negative thermal expansion material, characterized in that it is a composite of zinc-phosphorus composite oxide and metal pyrophosphate, wherein the zinc-phosphorus composite oxide comprises the zinc-phosphorus composite oxide shown in the following general formula (1): Zn x M y P z1 O t1 (1) (In the formula, M represents one or more elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. x represents 0.0 < x ≤ 2.0, y represents 0.0 ≤ y < 2.0, z1 represents 1.7 ≤ z1 ≤ 2.3, and t1 represents 6.0 ≤ t1 ≤ 8.0. Among these, 1.7 ≤ x + y ≤ 2.3.) The pyrophosphate metal salt comprises the pyrophosphate metal salt represented by the following general formula (2): A w P z2 O t2 (2) (In the formula, A represents one or more metallic elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w represents 1.7 ≤ w ≤ 2.3, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.0 ≤ t2 ≤ 8.0.)

[0013] In addition, the present invention (2) provides the negative thermal expansion material of (1), characterized in that the composite has a core-shell structure, the core comprising the zinc-phosphorus composite oxide represented by the above general formula (1), and the shell comprising the metal pyrophosphate salt represented by the above general formula (2).

[0014] In addition, the present invention (3) provides a negative thermal expansion material of (1) or (2), characterized in that the zinc-phosphorus composite oxide shown in the above general formula (1) is Zn2P2O7.

[0015] In addition, the present invention (4) provides a negative thermal expansion material of any one of (1) to (3), characterized in that the pyrophosphate metal salt shown in the above general formula (2) is Mn2P2O7 or Cu2P2O7.

[0016] In addition, the present invention (5) provides a negative thermal expansion material according to any one of (1) to (4), characterized in that the coefficient of thermal expansion of the negative thermal expansion material between 80 and 200°C is -23 × 10⁻⁶. -6 / K and below.

[0017] In addition, the present invention (6) provides a negative thermal expansion material of any one of (1) to (5), characterized in that the ratio (α2 / α1) of the coefficient of thermal expansion between 100 and 150°C to the coefficient of thermal expansion between 100 and 130°C is 2.5 or less.

[0018] In addition, the present invention (7) provides a negative thermal expansion material of any one of (1) to (6), characterized in that, when using Cu-Kα as an X-ray source for X-ray diffraction measurement, the peak of the main peak is observed between 2θ = 29.66 and 29.73° when 2θ is between 29 and 30°.

[0019] In addition, the present invention (8) provides a negative thermal expansion material of any one of (1) to (7), characterized in that the average particle size of the negative thermal expansion material is 0.1 to 100 μm.

[0020] In addition, the present invention (9) provides a negative thermal expansion material according to any one of (1) to (8), characterized in that the BET specific surface area of ​​the negative thermal expansion material is 0.05 to 50 m². 2 / g.

[0021] In addition, the present invention (10) provides a method for manufacturing a negative thermal expansion material, characterized in that a mixture comprising zinc-phosphorus composite oxide particles as shown in the following general formula (1) and an A source and a P source as raw materials for generating pyrophosphate metal salts as shown in the following general formula (2) is calcined. Zn x M y P z1 O t1 (1) (In the formula, M represents one or more elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. x represents 0 < x ≤ 2.0, y represents 0 ≤ y < 2.0, z1 represents 1.7 ≤ z1 ≤ 2.3, and t1 represents 6.0 ≤ t1 ≤ 8.0. Among these, 1.7 ≤ x + y ≤ 2.3.) A w P z2 O t2 (2) (In the formula, A represents one or more metallic elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w represents 1.7 ≤ w ≤ 2.3, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.0 ≤ t2 ≤ 8.0.)

[0022] In addition, the present invention (11) provides a method for manufacturing the negative thermal expansion material described in (10), characterized in that the zinc-phosphorus composite oxide shown in the above general formula (1) is obtained by calcining a reaction precursor containing at least zinc pyrophosphate.

[0023] In addition, the present invention (12) provides a composite material, characterized in that it includes a negative thermal expansion material and a positive thermal expansion material of any one of (1) to (9).

[0024] In addition, the present invention (13) provides a composite material of (12), characterized in that the above-mentioned positive thermal expansion material is selected from at least one of metal, alloy, glass, ceramic, rubber and resin.

[0025] Invention Effects According to the present invention, a negative thermal expansion material can be provided, which exhibits excellent negative thermal expansion properties and shows a gradual volume reduction with increasing temperature compared to existing zinc-phosphorus composite oxides such as Zn2P2O7. Attached Figure Description

[0026] Figure 1 This is the X-ray diffraction pattern of the negative thermal expansion material sample from Example 1.

[0027] Figure 2 This is the X-ray diffraction pattern of the negative thermal expansion material sample of Comparative Example 1.

[0028] Figure 3 This is an SEM image of the negative thermal expansion material sample from Example 1.

[0029] Figure 4 The image shown is an SEM photograph of the negative thermal expansion material sample from Reference Example 1.

[0030] Figure 5 This is an X-ray diffraction pattern of the negative thermal expansion material sample of Example 1 with 2θ between 29 and 30°.

[0031] Figure 6 The image shows the X-ray diffraction pattern of the negative thermal expansion material sample in Reference Example 1, with 2θ between 29° and 30°.

[0032] Figure 7 This is a graph showing the relationship between the thermal shrinkage rate (%) and temperature (°C) of ceramic molded bodies (made by heating to 700°C for 3 hours and firing for 4 hours) using negative thermal expansion material samples from Examples 1-3 and Comparative Example 1.

[0033] Figure 8 This is a graph showing the relationship between the thermal shrinkage rate (%) and temperature (°C) of ceramic molded bodies (made by heating to 750°C for 3 hours and firing for 4 hours) using negative thermal expansion material samples from Examples 1-3 and Comparative Example 1. Detailed Implementation

[0034] The present invention will now be described based on its preferred embodiments.

[0035] The negative thermal expansion material of the present invention is characterized in that it is a composite of zinc-phosphorus composite oxide and pyrophosphate metal salt. The zinc-phosphorus composite oxide comprises the zinc-phosphorus composite oxide represented by the following general formula (1): Zn x M y P z1 O t1 (1) (In the formula, M represents one or more elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. x represents 0.0 < x ≤ 2.0, y represents 0.0 ≤ y < 2.0, z1 represents 1.7 ≤ z1 ≤ 2.3, and t1 represents 6.0 ≤ t1 ≤ 8.0. Among these, 1.7 ≤ x + y ≤ 2.3.) The pyrophosphate metal salt comprises the pyrophosphate metal salt represented by the following general formula (2): A w P z2 O t2 (2) (In the formula, A represents one or more metallic elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w represents 1.7 ≤ w ≤ 2.3, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.0 ≤ t2 ≤ 8.0.)

[0036] The negative thermal expansion material of the present invention is a composite of zinc-phosphorus composite oxide and pyrophosphate metal salt. Moreover, the negative thermal expansion material of the present invention is a composite of zinc-phosphorus composite oxide mainly comprising the zinc-phosphorus composite oxide shown in general formula (1) and pyrophosphate metal salt mainly comprising the pyrophosphate metal salt shown in general formula (2).

[0037] In general formula (1), M is an element included as needed for the purpose of further adjusting the negative thermal expansion. M represents one or more elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. In this invention, among these, especially considering excellent negative thermal expansion and a gradual volume reduction with increasing temperature, M is preferably Mg, Mn, or Cu.

[0038] In general formula (1), x is 0.0 < x ≤ 2.0. From the viewpoint of excellent negative thermal expansion characteristics, x is preferably 1.5 ≤ x ≤ 2.0, and particularly preferably 1.6 ≤ x ≤ 2.0.

[0039] In general formula (1), y is 0.0≤y<2.0. From the viewpoint of excellent negative thermal expansion characteristics, y is preferably 0≤y≤1.9, and particularly preferably 0≤y≤1.8.

[0040] In general formula (1), z1 is 1.7≤z1≤2.3. From the viewpoint of excellent negative thermal expansion characteristics, z1 is preferably 1.8≤z1≤2.2, and particularly preferably 1.9≤z1≤2.1.

[0041] In general formula (1), t1 is 6.0≤t1≤8.0. From the viewpoint of excellent negative thermal expansion characteristics, t1 is preferably 6.5≤t1≤7.5, and particularly preferably 6.2≤t1≤7.2.

[0042] In general formula (1), x + y is 1.7 ≤ x + y ≤ 2.3. Considering the higher negative thermal expansion characteristics, x + y is preferably 1.8 ≤ x + y ≤ 2.2.

[0043] In general formula (2), A represents one or more metallic elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy and Ho. Among these, Mn and Cu are particularly preferred from the viewpoint of excellent negative thermal expansion and a gradual volume reduction with increasing temperature.

[0044] In general formula (2), w is 1.7≤w≤2.3. Considering the viewpoint that the volume reduction is moderate with the increase of temperature and the negative thermal expansion characteristics are also excellent, w is 1.8≤w≤2.2, and is particularly preferred to be 1.9≤w≤2.1.

[0045] In general formula (2), z2 is 1.7≤z2≤2.3. From the viewpoint that the volume reduction is moderate with the increase of temperature and the negative thermal expansion characteristics are also excellent, z2 is preferably 1.8≤z2≤2.2, and particularly preferably 1.9≤z2≤2.1.

[0046] In general formula (2), t2 is 6.0≤t2≤8.0. From the viewpoint that the volume reduction is gradual with the increase of temperature and the negative thermal expansion characteristics are also excellent, t2 is preferably 6.5≤t2≤7.5, and particularly preferably 6.2≤t2≤7.2.

[0047] The pyrophosphate metal salt shown in general formula (2) has a lower phase transition temperature compared to the zinc-phosphorus composite oxide shown in general formula (1). Moreover, in the negative thermal expansion material of the present invention, by combining the zinc-phosphorus composite oxide shown in general formula (1) with the pyrophosphate metal salt shown in general formula (2), which has a lower phase transition temperature, the following effects can be achieved: excellent negative thermal expansion properties, and a gradual volume reduction with increasing temperature compared to existing zinc-phosphorus composite oxides such as Zn2P2O7.

[0048] Examples of composite forms related to the negative thermal expansion material of this invention include: a) A simple mixture of zinc-phosphorus composite oxide particles of general formula (1) and metal pyrophosphate particles of general formula (2); b) A composite having a core-shell structure, having a core comprising a zinc-phosphorus composite oxide of general formula (1) and a shell comprising a metal pyrophosphate salt of general formula (2) covering all or part of the surface of the core; c) A composite having a core-shell structure, having a core containing a metal pyrophosphate salt of general formula (2), and a shell containing a zinc-phosphorus composite oxide of general formula (1) covering all or part of the surface of the core; d) A composite consisting of particles of zinc-phosphorus composite oxide as shown in general formula (1) and particles of metal pyrophosphate as shown in general formula (2).

[0049] In configuration b), the core is primarily formed of a zinc-phosphorus composite oxide comprising the zinc-phosphorus composite oxide shown in general formula (1). That is, in configuration b), the core may be formed solely of the zinc-phosphorus composite oxide shown in general formula (1), or it may be formed of a zinc-phosphorus composite oxide shown in general formula (1) containing element A and / or other impurity elements within a range that does not exert the effects of the present invention, for example, within a range of 0.5% by mass or less relative to the zinc-phosphorus composite oxide shown in general formula (1). Furthermore, in configuration b), the shell is primarily formed of a pyrophosphate metal salt comprising the pyrophosphate metal salt shown in general formula (2). That is, in configuration b), the shell may be formed solely of the pyrophosphate metal salt shown in general formula (2), or it may be formed of a pyrophosphate metal salt shown in general formula (2) containing element Zn, element M, and / or other impurity elements within a range that does not exert the effects of the present invention, for example, within a range of 0.5% by mass or less relative to the pyrophosphate metal salt shown in general formula (2).

[0050] In configuration c), the core is primarily formed of a pyrophosphate metal salt comprising the pyrophosphate metal salt shown in general formula (2). That is, in configuration c), the core may be formed solely of the pyrophosphate metal salt shown in general formula (2), or it may be formed of the pyrophosphate metal salt shown in general formula (2) containing Zn, M, and / or other impurity elements in a range that does not exert the effects of the present invention, for example, in a range of 0.5% by mass or less relative to the pyrophosphate metal salt shown in general formula (2). Furthermore, in configuration c), the shell is primarily formed of a zinc-phosphorus composite oxide comprising the zinc-phosphorus composite oxide shown in general formula (1). That is, in configuration c), the shell may be formed solely of the zinc-phosphorus composite oxide shown in general formula (1), or it may be formed of the zinc-phosphorus composite oxide shown in general formula (1) containing A and / or other impurity elements in a range that does not exert the effects of the present invention, for example, in a range of 0.5% by mass or less relative to the zinc-phosphorus composite oxide shown in general formula (1).

[0051] As d), examples include core particles consisting only of zinc-phosphorus composite oxides of general formula (1), or core particles consisting of zinc-phosphorus composite oxides of general formula (1) containing A element and / or impurity elements in a range of less than 0.5% by mass relative to the zinc-phosphorus composite oxides of general formula (1) without exerting the effects of the present invention; and composites consisting of coated particles consisting only of pyrophosphate metal salts of general formula (2) that coat part or all of the surface of the core particles and are attached thereto, or attached particles consisting of pyrophosphate metal salts of general formula (2) containing Zn element, M element and / or other impurity elements in a range of less than 0.5% by mass relative to the pyrophosphate salts of general formula (2) without exerting the effects of the present invention.

[0052] Additionally, as d), examples include core particles consisting solely of the metal pyrophosphate salt of general formula (2), or core particles consisting of the metal pyrophosphate salt of general formula (2) containing Zn, M and / or other impurity elements in a range of less than 0.5% by mass relative to the metal pyrophosphate salt of general formula (2) without exerting the effects of the present invention; and composites consisting solely of coated particles consisting of zinc-phosphorus composite oxide of general formula (1) covering part or all of the surface of the core particles and attached thereto, or attached particles consisting of zinc-phosphorus composite oxide of general formula (1) containing A and / or other impurity elements in a range of less than 0.5% by mass relative to the zinc-phosphorus composite oxide of general formula (1) without exerting the effects of the present invention.

[0053] Moreover, in the above-mentioned forms, especially from the viewpoint of excellent negative thermal expansion and a gradual reduction in volume with increasing temperature, b) is preferred as a composite having a core-shell structure, having a core containing a zinc-phosphorus composite oxide as shown in general formula (1) and a shell containing a metal pyrophosphate salt as shown in general formula (2) covering all or part of the surface of the core.

[0054] In the negative thermal expansion material of the present invention, especially from the viewpoint of excellent negative thermal expansion and a gradual volume reduction with increasing temperature, the zinc-phosphorus composite oxide represented by general formula (1) is preferably Zn2P2O7, and the pyrophosphate metal salt represented by general formula (2) is Mn2P2O7 and / or Cu2P2O7.

[0055] For example, when the zinc-phosphorus composite oxide shown in general formula (1) is Zn2P2O7, the negative thermal expansion material of the present invention preferably exhibits a gradual volume reduction with increasing temperature in the temperature range of 100 to 150°C.

[0056] Regarding the content ratio of zinc-phosphorus composite oxide of general formula (1) to pyrophosphate metal salt of general formula (2) in the composite of negative thermal expansion materials involved in the present invention, the ratio is preferably 0.002 to 0.50, particularly preferably 0.005 to 0.30, based on the molar ratio of pyrophosphate metal salt of general formula (2) to zinc-phosphorus composite oxide of general formula (1) (pyrophosphate metal salt of general formula (2) / zinc-phosphorus composite oxide of general formula (1)). When the molar ratio of pyrophosphate metal salt of general formula (2) to zinc-phosphorus composite oxide of general formula (1) is within the above range, the negative thermal expansion properties are excellent, and the gradual volume reduction effect is further improved with the increase of temperature.

[0057] The negative thermal expansion material of the present invention preferably exhibits a main peak peak at 2θ = 29.66–29.73° when X-ray diffraction is performed using Cu-Kα as an X-ray source, with the peak between 2θ = 29.66–29.73°, within a range of 2θ = 29–30°. The negative thermal expansion material composed of existing Zn₂P₂O₇ or a zinc-phosphorus composite oxide in which a portion of the zinc in Zn₂P₂O₇ is replaced by other metal elements, also exhibits a main peak peak peak near 2θ = 29.65°, which is smaller than 29.66°, when X-ray diffraction is performed using Cu-Kα as an X-ray source, within a range of 2θ = 29.66° (see reference). Figure 6 In contrast, the negative thermal expansion material involved in this invention has a 2θ between 29 and 30°, and the peak of the main peak is observed at 2θ = 29.66 to 29.73° (see reference). Figure 5 ).

[0058] The BET specific surface area of ​​the negative thermal expansion material of the present invention is not particularly limited, but is preferably 0.05 to 50 m². 2 / g, particularly preferably 0.10-10mg 2 / g, more preferably 0.20-8m 2 / g. By ensuring the BET specific surface area of ​​the negative thermal expansion material is within the above-mentioned range, operation becomes easier when using the negative thermal expansion material as a filler for resins or glass, etc. Furthermore, in this invention, the BET specific surface area of ​​the negative thermal expansion material is a value measured using the fully automated specific surface area measuring device Macsorb (manufactured by MOUNTECH) via the BET single-point method.

[0059] The average particle size of the negative thermal expansion material of the present invention is not particularly limited, but is preferably 0.1 to 100 μm, particularly preferably 0.2 to 80 μm, and even more preferably 0.2 to 20 μm, based on the average particle size obtained by scanning electron microscopy. By ensuring the average particle size of the negative thermal expansion material is within the above range, operation becomes easier when using the negative thermal expansion material as a filler for resins or glass, etc. Furthermore, in the present invention, the average particle size of the negative thermal expansion material is determined by the arithmetic mean of the particle sizes of 50 randomly selected particles at 1000x magnification during scanning electron microscopy. In this case, the particle size refers to the maximum length (maximum length) of the line segment traversing the two-dimensional projection image of the particle.

[0060] The particle shape of the negative thermal expansion material of the present invention is not particularly limited, and can be, for example, spherical, granular, plate-like, scaly, whisker-like, rod-like, filamentous, or fragment-like.

[0061] The negative thermal expansion material of the present invention only needs to have a coefficient of thermal expansion of less than 0 between 80 and 200°C, without limitation. The coefficient of thermal expansion of the negative thermal expansion material of the present invention between 80 and 200°C is -23 × 10⁻⁶.-6 / K or less, preferably -20×10 -6 Below / K, there are no specific restrictions on the lower limit value, which is approximately -100×10 -6 / K or above, preferably -70×10 -6 / K or higher. In the negative thermal expansion material of the present invention, considering that the coefficient of thermal expansion is easily offset by the positive expansion when combined with a positive thermal expansion material, the coefficient of thermal expansion between 80 and 200°C is particularly preferably -10 × 10. -6 ~-50×10 -6 / K.

[0062] Furthermore, in this invention, the coefficient of thermal expansion between 80 and 200°C is determined through the following steps. First, 0.05 g of propylene carbonate is added to 1.00 g of the sample, and the mixture is pulverized and mixed in a mortar for 3 minutes. Then, 0.15 g is weighed and completely filled into a φ6 mm mold. Next, a powder molded body is formed using a manual press at a pressure of 0.5 t. The resulting powder molded body is heated to 700°C in an electric furnace for 3 hours and held for 4 hours to produce a ceramic molded body. Then, the coefficient of thermal expansion of the ceramic molded body is measured using a thermomechanical measuring device (e.g., NETZSCH JAPAN TMA4000SE). The measurement conditions are set as nitrogen atmosphere, load 10 g, and temperature range 50°C to 225°C. The measurement is repeated twice within the temperature range of 50°C to 225°C, and the coefficient of thermal expansion between 80 and 200°C obtained from the second measurement is taken as the coefficient of thermal expansion of the negative thermal expansion material.

[0063] The negative thermal expansion material involved in this invention, for example, when Zn2P2O7 is used as a zinc-phosphorus composite oxide as in general formula (1), exhibits a more gradual decrease in volume with increasing temperature between 100 and 150°C compared to conventional Zn2P2O7 negative thermal expansion materials. Furthermore, the ratio (α2 / α1) of the coefficient of thermal expansion between 100 and 150°C to the coefficient of thermal expansion between 100 and 130°C is approximately 2.7 for conventional Zn2P2O7 negative thermal expansion materials, but in this invention, when Zn2P2O7 is used as a zinc-phosphorus composite oxide as in general formula (1), it is 2.5 or less, preferably 0.5 to 2.5.

[0064] Furthermore, since the ratio of α2 to α1 is smaller, a gradual volume reduction is observed with increasing temperature in the temperature range of 100–150°C.

[0065] In this invention, the degree of volume reduction accompanying temperature increase between 100 and 150°C is determined by the following steps.

[0066] First, 0.05g of propylene carbonate was added to 1.00g of the sample, and the mixture was pulverized and mixed in a mortar for 3 minutes. 0.15g of the pulverized mixture was then weighed and filled into a φ6mm mold. Next, a powder molded body was formed using a manual press at a pressure of 0.5t. The resulting powder molded body was then heated to 700℃ in an electric furnace over 3 hours and held for 4 hours to produce a ceramic molded body. The coefficient of thermal expansion of the ceramic molded body was then measured using a thermomechanical measuring device (NETZSCH JAPAN TMA4000SE). The measurement conditions were set as follows: nitrogen atmosphere, load 10g, temperature range 50℃~225℃, and the measurement was repeated twice. The degree of volume reduction with increasing temperature was evaluated by calculating the ratio of the coefficient of thermal expansion (α2) between 100~150℃ to the coefficient of thermal expansion (α1) between 100~130℃ in the second measurement.

[0067] Hereinafter, as a preferred method for manufacturing the negative thermal expansion material of the present invention, a method for manufacturing a composite having the core-shell structure described above (b), having a core comprising a zinc-phosphorus composite oxide as shown in general formula (1) and a shell comprising a metal pyrophosphate salt as shown in general formula (2) covering all or part of the surface of the core will be described.

[0068] The method for manufacturing the negative thermal expansion material of the present invention is characterized by firing a mixture of A source and P source required for the generation of zinc-phosphorus composite oxide as shown in general formula (1) and pyrophosphate metal salt as shown in general formula (2).

[0069] Zn x M y P z1 O t1 (1) (In the formula, M represents one or more elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. x represents 0 < x ≤ 2.0, y represents 0 ≤ y < 2.0, z1 represents 1.7 ≤ z1 ≤ 2.3, and t1 represents 6.0 ≤ t1 ≤ 8.0. Among these, 1.7 ≤ x + y ≤ 2.3.) A w P z2 O t2 (2) (In the formula, A represents one or more metallic elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho. w represents 1.7 ≤ w ≤ 2.3, z2 represents 1.7 ≤ z2 ≤ 2.3, and t2 represents 6.0 ≤ t2 ≤ 8.0.)

[0070] That is, the negative thermal expansion material of the present invention is manufactured by a manufacturing method including the following steps A and B.

[0071] Step A: The process of preparing a mixture of raw materials containing the A source and P source required for the generation of the zinc-phosphorus composite oxide shown in general formula (1) and the pyrophosphate metal salt shown in general formula (2).

[0072] Step B: The process of firing the raw material mixture to obtain a negative thermal expansion material.

[0073] Regarding the various physical properties of the zinc-phosphorus composite oxide represented by the above general formula (1) involved in step A, from the viewpoint of making operation easier when using a negative thermal expansion material as a filler for resin or glass, the average particle size obtained by scanning electron microscopy is preferably 0.1 to 100 μm, more preferably 0.2 to 80 μm.

[0074] From the viewpoint that it is easier to operate when using negative thermal expansion materials as fillers for resins or glass, etc., it is preferable that the BET specific surface area of ​​the zinc-phosphorus composite oxide shown in general formula (1) is 0.05 to 50 m². 2 / g, preferably 0.1-10m 2 / g.

[0075] In the method for manufacturing the negative thermal expansion material of the present invention, from the viewpoint of being able to advantageously manufacture the negative thermal expansion material in industry, it is preferable that the zinc-phosphorus composite oxide represented by the general formula (1) involved in the A step is the product obtained by the following steps.

[0076] The first step: the process of preparing a reaction precursor containing Zn, P, and M element added as needed.

[0077] The second step is to calcine the above-mentioned reaction precursor to obtain the zinc-phosphorus composite oxide shown in general formula (1).

[0078] The first step is to prepare a reaction precursor containing Zn, P, and M element added as needed.

[0079] The reaction precursor can be produced by mixing Zn compounds, phosphorus compounds, and M-containing compounds as needed.

[0080] Zn compounds are compounds containing Zn atoms. Examples of Zn compounds include zinc salts of organic carboxylic acids such as zinc gluconate, zinc citrate, zinc acetate, and zinc lactate, zinc salts of inorganic acids, zinc oxides, zinc hydroxides, zinc phosphates, and zinc pyrophosphates.

[0081] Phosphorus compounds are compounds containing phosphorus atoms. Phosphoric acid is preferred as a phosphorus compound. Additionally, compounds containing both Zn and P sources, such as zinc phosphates and zinc pyrophosphates, can function as both Zn and phosphorus compounds. Furthermore, zinc phosphates and zinc pyrophosphates can be aqueous or anhydrous.

[0082] The compound containing element M added as needed is a compound that contains element M. Examples of compounds containing element M include carbonates, oxides, hydroxides, halides, and carboxylates of M. Examples of carboxylates of M include gluconate, citrate, oxalate, acetate, and lactate.

[0083] From the viewpoint that the reaction precursors of the first step are inexpensive and easy to obtain with simple operation, and that the zinc-phosphorus composite oxides of the general formula (1) which are single phase on X-ray diffraction can be easily obtained by firing the obtained reaction precursors in the second step described later, it is preferred that the reaction precursors of the first step contain at least zinc pyrophosphate hydrate.

[0084] Furthermore, regarding the reaction precursor containing at least zinc pyrophosphate, in the case of manufacturing Zn2P2O7 of general formula (1) where y is 0, the reaction precursor contains only zinc pyrophosphate, while in the case of manufacturing zinc-phosphorus composite oxide of general formula (1) containing element M, the reaction precursor contains zinc pyrophosphate, phosphorus compound and element M compound.

[0085] In the first step, it is preferable to appropriately adjust the contents of zinc compound, phosphorus compound and M-containing compound so that the molar ratio of each atom of Zn, P and M in the reaction precursor becomes the composition of zinc-phosphorus composite oxide as shown in general formula (1).

[0086] Furthermore, when using zinc phosphate or zinc pyrophosphate as zinc compounds, it is preferable to also take into account the amount of phosphorus atoms in the zinc compound when preparing the reaction precursor.

[0087] In the first step, zinc compounds, phosphorus compounds, and compounds containing element M can be mixed as needed. This mixing process can be carried out wet or dry.

[0088] In the case of wet mixing, the reaction precursor can be obtained by completely drying and removing the solvent.

[0089] Furthermore, in the first process, the composition of the zinc-phosphorus composite oxide obtained by drying and removing the solvent after wet mixing is basically consistent with the atomic molar ratio of Zn, P, and M when each raw material is added.

[0090] The second step is to calcine the reaction precursor prepared in the first step to obtain the zinc-phosphorus composite oxide shown in general formula (1).

[0091] The firing temperature in the second step is preferably 300–900°C, more preferably 500–800°C. On the other hand, when the firing temperature in the second step is lower than the above range, there is a tendency for the formation of the zinc-phosphorus composite oxide shown in general formula (1) to become insufficient, and when it exceeds the above range, there is a tendency for it to become a solidified sintered body. There is no particular limitation on the firing time in the second step, and the firing is carried out sufficiently until the zinc-phosphorus composite oxide shown in general formula (1) is formed.

[0092] Regarding the generation of the zinc-phosphorus composite oxide shown in general formula (1), it can be confirmed, for example, by X-ray diffraction analysis whether a single-phase zinc-phosphorus composite oxide shown in general formula (1) has been obtained.

[0093] In the second process, in most cases, the reaction precursor can be almost completely converted into the zinc-phosphorus composite oxide shown in the above general formula (1) with a firing time of 0.5 hours or more, preferably 2 to 20 hours.

[0094] There are no special restrictions on the firing atmosphere in the second process; it can be carried out under any atmosphere, including inert gas atmosphere, vacuum atmosphere, oxidizing gas atmosphere, or atmospheric atmosphere.

[0095] In the second process, firing can be performed once or multiple times as needed. For example, to ensure uniform powder properties, the material that has been fired once can be pulverized and then fired again.

[0096] After firing, it can be cooled appropriately and then crushed, broken, or graded as needed.

[0097] The A source involved in step A is a compound containing the element A. Examples of A sources include carbonates, oxides, hydroxides, halides, and carboxylates of A. Examples of carboxylates of A include gluconic acid, citrate, oxalate, acetate, and lactate.

[0098] The P source involved in step A is a compound having P atoms. Phosphoric acid is preferred as the P source.

[0099] The A source and P source involved in step A can be phosphates or pyrophosphates that simultaneously contain A and P atoms. Furthermore, phosphates and pyrophosphates can be aqueous or anhydrous.

[0100] In step A, it is preferable to adjust the mixing amount of source A and source P appropriately so that the atomic molar ratio of A and P in the raw material mixture becomes the composition of the metal pyrophosphate salt shown in general formula (2).

[0101] Furthermore, in step A, it is preferable to adjust the mixing amounts of the zinc-phosphorus composite oxide, source A, and source P shown in general formula (1) so that, relative to 100 parts by mass of the zinc-phosphorus composite oxide shown in general formula (1) in the generated negative thermal expansion material, the pyrophosphate metal salt shown in general formula (2) is 0.1 to 20 parts by mass, preferably 0.2 to 15 parts by mass.

[0102] In step A, the zinc-phosphorus composite oxide, source A and source P shown in general formula (1) can be mixed in a wet or dry manner.

[0103] When performing wet mixing, it is preferable to remove the solvent completely by drying to obtain the raw material mixture.

[0104] Step B is the process of firing the raw material mixture prepared in step A to obtain a composite of zinc-phosphorus composite oxide as shown in general formula (1) and pyrophosphate metal salt as shown in general formula (2), which is the negative thermal expansion material of the present invention.

[0105] The firing temperature in step B is preferably 300–850°C, more preferably 350–800°C. On the other hand, if the firing temperature in step B is lower than the above range, there is a tendency for the formation of the pyrophosphate metal salt shown in general formula (2) to become insufficient, and if it exceeds the above range, there is a tendency for it to become a solidified sintered body. The firing time in step B is not particularly limited, and it is carried out until the pyrophosphate metal salt shown in general formula (2) is formed.

[0106] Regarding the formation of the metal pyrophosphate salt shown in general formula (2), for example, the formation of the metal pyrophosphate salt shown in general formula (2) can be confirmed by X-ray diffraction analysis to see whether the peak of the main peak is observed between 2θ = 29.66 and 29.73° when 2θ is between 29 and 30°.

[0107] In step B, in most cases, the negative thermal expansion material of the present invention can be obtained with a firing time of 0.5 hours or more, preferably 1 to 10 hours.

[0108] There are no special restrictions on the firing atmosphere in step B; it can be carried out under any atmosphere, including inert gas atmosphere, vacuum atmosphere, oxidizing gas atmosphere, or atmospheric atmosphere.

[0109] In step B, firing can be performed once or multiple times as needed. For example, to ensure uniform powder properties, the material that has been fired once can be pulverized and then fired again.

[0110] After firing, it can be cooled appropriately and then crushed, broken, graded, etc., as needed to obtain a negative thermal expansion material with a core-shell structure. It is a composite material having a core containing a zinc-phosphorus composite oxide as shown in general formula (1) and a shell containing a metal pyrophosphate salt as shown in general formula (2) covering all or part of the surface of the core.

[0111] Furthermore, regarding the method of obtaining a simple mixture of zinc-phosphorus composite oxide particles of general formula (1) and pyrophosphate metal salt particles of general formula (2) as a composite, one example is a method of mixing zinc-phosphorus composite oxide of general formula (1) and pyrophosphate metal salt of general formula (2) by mechanical means of applying strong shear force under dry or wet conditions.

[0112] In addition, regarding the method of manufacturing the above-mentioned c) having a core-shell structure, having a core containing a metal pyrophosphate salt of general formula (2) and a shell containing a zinc phosphorus composite oxide of general formula (1) covering all or part of the surface of the core, an example can be given: a method of firing a mixture containing a reaction precursor of metal pyrophosphate salt of general formula (2) which serves as the core and zinc phosphorus composite oxide of general formula (1) obtained in the first step above at 300 to 850°C.

[0113] In addition, regarding the method of manufacturing the above-mentioned d) composite containing the zinc phosphorus composite oxide particles of general formula (1) and the pyrophosphate metal salt particles of general formula (2), an example can be given: a method of heat-treating a homogeneous mixture of the zinc phosphorus composite oxide particles of general formula (1) and the pyrophosphate metal salt particles of general formula (2) at 300 to 850°C.

[0114] The average particle size of the negative thermal expansion material obtained by the manufacturing method of the present invention is preferably 0.1 to 100 μm, particularly preferably 0.2 to 80 μm, and even more preferably 0.2 to 20 μm, and the BET specific surface area is 0.05 to 50 m². 2 / g, particularly preferably 0.10-10mg 2 / g, more preferably 0.20-8m 2 / g. When considering the use of negative thermal expansion materials as fillers in resins or glass, operation becomes easier, and it is preferable that the average particle size and / or BET specific surface area of ​​the negative thermal expansion materials are within the above-mentioned range.

[0115] Furthermore, in order to improve the resin dispersibility and moisture resistance of the negative thermal expansion material according to the present invention, the surface of the particles can be surface-treated as needed. Additionally, in the manufacturing method of the negative thermal expansion material according to the present invention, in order to improve the resin dispersibility and moisture resistance of the negative thermal expansion material, the negative thermal expansion material obtained in step B can be surface-treated as needed.

[0116] As a surface treatment, examples include methods for coating the particle surface with silane coupling agents, titanate coupling agents, fatty acids or their derivatives, or inorganic compounds containing one or more elements selected from Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe, and Zr (see, for example, WO2020 / 095837, WO2020 / 261976, WO2019 / 087722, and Japanese Patent Application Publication No. 2020-147486). Furthermore, these methods can be appropriately combined for surface treatment.

[0117] The negative thermal expansion material obtained by the manufacturing method of the present invention has a coefficient of thermal expansion of -23 × 10⁻⁶ between 80 and 200 °C. -6 / K or less, preferably -20×10 -6 Below / K, there are no specific restrictions on the lower limit value, which is approximately -100×10 -6 / K or above, preferably -70×10 -6 / K or higher. In the negative thermal expansion material of the present invention, considering that the coefficient of thermal expansion can easily offset the positive expansion when combined with a positive thermal expansion material, it is particularly preferred to be -10×10 -6 ~-50×10 -6 / K.

[0118] Furthermore, in the negative thermal expansion material obtained by the manufacturing method of the negative thermal expansion material of the present invention, when Zn2P2O7 is used as the zinc-phosphorus composite oxide of general formula (1), it is preferable that the ratio (α2 / α1) of the coefficient of thermal expansion between 100 and 150°C to the coefficient of thermal expansion between 100 and 130°C, which represents the degree of volume reduction with temperature increase between 100 and 150°C, is 2.5 or less, preferably 0.5 to 2.5.

[0119] The negative thermal expansion material of the present invention is used in the form of powder or paste. When using the negative thermal expansion material of the present invention in the form of paste, the negative thermal expansion material of the present invention is mixed and dispersed in a solvent and / or a low-viscosity liquid resin, and used in the state of paste. Alternatively, the negative thermal expansion material of the present invention may be dispersed in a solvent and / or a low-viscosity liquid resin, and further contained, as needed, with binders, fluxes, dispersants, etc., and used in the state of paste.

[0120] The negative thermal expansion material of the present invention can be used in combination with various organic or inorganic compounds that are positive thermal expansion materials to form composite materials. The composite materials of the present invention comprise the negative thermal expansion material and the positive thermal expansion material of the present invention.

[0121] Organic compounds used as materials for positive thermal expansion are not particularly limited and can include: rubber, polyolefins, polycyclic olefins, polystyrene, ABS, polyacrylates, polyphenylene sulfide, phenolic resins, polyamide resins, polyimide resins, epoxy resins, silicone resins, polycarbonate resins, polyethylene resins, polypropylene resins, polyethylene terephthalate resins (PET resins), and polyvinyl chloride resins, etc. In addition, inorganic compounds used as materials for positive thermal expansion can include silica, silicates, graphite, sapphire, various glass materials, concrete materials, and various ceramic materials, etc.

[0122] Since the composite material of the present invention contains the negative thermal expansion material of the present invention with excellent negative thermal expansion characteristics, it is possible to achieve negative thermal expansion rate, zero thermal expansion rate or low thermal expansion rate depending on the mixing ratio with other compounds.

[0123] Example The present invention is illustrated below by way of examples, but the present invention is not limited thereto.

[0124] (X-ray diffraction device) In the embodiments, measurements were performed using an X-ray diffraction apparatus (Ultima IV manufactured by Rigaku Corporation) under the following measurement conditions.

[0125] X-ray source: Cu-Kα Tube voltage: 40kV Tube current: 40mA Scanning speed: 1° / sec Smoothing: Weighted Averaging Kα2 removal: strength ratio 0.5 <Zn2P2O7 Sample Preparation> Zinc pyrophosphate trihydrate (Zn₂P₂O₇•3H₂O, average particle size 1.2 μm) was calcined at 700 °C for 4 hours. X-ray diffraction analysis of the calcined powder showed that it was a single-phase α-Zn₂P₂O₇.

[0126] Furthermore, the average particle size of the obtained Zn₂P₂O₇ sample was 1.1 μm, and the BET specific surface area was 0.6 m². 2 / g.

[0127] The average particle size of the Zn2P2O7 sample was calculated by taking the average value of 50 randomly selected particles at 1000x magnification during scanning electron microscopy.

[0128] (Example 1) <Process A> The prepared Zn₂P₂O₇ sample (5.000 g), manganese carbonate (0.0943 g, average particle size 1.6 μm), 85% phosphoric acid (0.0946 g), and pure water (10 mL) were thoroughly pulverized and mixed in a mortar. The mixture was then dried at 130 °C.

[0129] <Process B> The obtained dried powder was calcined at 700℃ for 4 hours. X-ray diffraction analysis of the calcined powder revealed peaks originating from α-Zn₂P₂O₇. Figure 1 It was used as a sample of a material with negative thermal expansion.

[0130] (Example 2) <Process A> The prepared Zn₂P₂O₇ sample (5.000 g), manganese carbonate (0.0472 g, average particle size 1.6 μm), 85% phosphoric acid (0.0473 g), and pure water (10 mL) were thoroughly pulverized and mixed in a mortar. Then, the mixture was dried at 130 °C.

[0131] <Process B> The obtained dried powder was calcined at 700℃ for 4 hours. X-ray diffraction analysis of the calcined powder revealed peaks originating from α-Zn₂P₂O₇. This powder was then used as a negative thermal expansion material sample.

[0132] (Comparative Example 1) The Zn₂P₂O₇ sample prepared above was used as a negative thermal expansion material sample (Zn₂P₂O₇). The X-ray diffraction pattern is shown below. Figure 2 .

[0133] (See Example 1 for reference) 3.5516 g of zinc pyrophosphate trihydrate (Zn₂P₂O₇•3H₂O, average particle size 1.2 μm), 0.1198 g of manganese carbonate (average particle size 1.6 μm), 0.1201 g of 85% phosphoric acid, and 10 mL of pure water were thoroughly pulverized and mixed in a mortar. The mixture was then dried at 130 °C. The resulting dried powder was calcined at 700 °C for 4 hours. X-ray diffraction analysis of the calcined powder revealed peaks originating from α-Zn₂P₂O₇. This was used as a reference sample (Zn₂P₂O₇). 1.90 Mn 0.10 P2O7).

[0134] (Physical property evaluation) The average particle size, BET specific surface area, main peak at 2θ = 29–30°, and coefficient of thermal expansion of the samples obtained in the Examples, Comparative Examples, and Reference Examples were determined. The average particle size and coefficient of thermal expansion were measured using an X-ray diffraction apparatus as described below. The results are presented in Tables 1 and 2.

[0135] In addition, SEM images of the negative thermal expansion material samples obtained in Example 1 and Reference Example 1 are shown in [the figures]. Figure 3 and Figure 4 Furthermore, the X-ray diffraction patterns of the samples of Example 1 and Reference Example 1 measured using an X-ray diffraction apparatus, between 2θ = 29 and 30°, are shown below. Figure 5 and Figure 6 .

[0136] (Average particle size) The average particle size of the negative thermal expansion material sample was determined by averaging 50 randomly selected particles at 1000x magnification during scanning electron microscopy.

[0137] [Determination of the coefficient of thermal expansion] (Making of the molded object) Add 0.05g of propylene carbonate to 1.00g of the sample, pulverize and mix in a mortar for 3 minutes, weigh 0.15g, and fill the entire mixture into a φ6mm mold. Then, use a manual press to mold the powder body at a pressure of 0.5t. Heat the resulting powder body in an electric furnace to 700℃ over 3 hours and maintain the temperature for 4 hours to produce a ceramic body.

[0138] For the manufactured ceramic molded body, the coefficient of thermal expansion between 80 and 200°C and the degree of linear expansion accompanying temperature rise between 100 and 150°C are evaluated as described below.

[0139] (Determination of the coefficient of thermal expansion between 80 and 200℃) For the fabricated ceramic molded body, the coefficient of thermal expansion was determined using a thermomechanical measuring apparatus (NETZSCH JAPAN TMA4000SE). The measurement conditions were set as follows: nitrogen atmosphere, load 10g, temperature range 50℃~225℃, repeated twice. The coefficient of thermal expansion between 80~200℃ from the second repeated measurement was taken as the coefficient of thermal expansion of the negative thermal expansion material sample.

[0140] In addition, the relationship between the thermal shrinkage rate (%) and temperature (°C) of the negative thermal expansion material sample is expressed as follows: Figure 7 .

[0141] Furthermore, the coefficient of thermal expansion was also measured for ceramic molds obtained by sintering the aforementioned ceramic molds (made by heating to 700°C in 3 hours and holding for 4 hours) and then heating to 750°C in 3 hours and holding for 4 hours. The relationship between the thermal shrinkage rate (%) and temperature (°C) of the negative thermal expansion material sample at this time is expressed as follows: Figure 8 .

[0142] (Evaluation of the degree of volume reduction accompanying temperature increase between 100 and 150°C) For the fabricated ceramic molded bodies, the coefficient of thermal expansion was determined using a thermomechanical measuring apparatus (NETZSCH JAPAN TMA4000SE). The measurement was repeated twice under nitrogen atmosphere, with a load of 10 g and a temperature range of 50°C to 225°C. The degree of volume reduction with increasing temperature was evaluated by comparing the coefficient of thermal expansion (α1) between 100 and 130°C and (α2) between 100 and 150°C in the second repetition.

[0143] The smaller the ratio of α2 to α1, the more gradual the volume reduction occurs with increasing temperature.

[0144] [Table 1] [Table 2] (Note) "-" in the table indicates that it was not measured. In addition, in Comparative Example 1, the ceramic molded body prepared by heating the dried powder to 750°C for 3 hours and holding it for 4 hours had a linear expansion coefficient of -53 ppm / K at 80-200°C, a linear expansion coefficient (α1′) of -32 ppm / K at 100-130°C, and a linear expansion coefficient (α2′) of -119 ppm / K at 100-150°C, with α2′ / α1′ being 3.7.

[0145] (Example 3) <Process A> 5.000 g of the Zn₂P₂O₇ sample, 0.1457 g of copper pyrophosphate trihydrate (average particle size 0.5 μm), and 10 mL of pure water were thoroughly pulverized and mixed in a mortar. The mixture was then dried at 130 °C.

[0146] <Process B> The obtained dried powder was calcined at 700℃ for 4 hours. X-ray diffraction analysis of the calcined powder revealed peaks originating from α-Zn₂P₂O₇. This powder was then used as a negative thermal expansion material sample.

[0147] In addition, the average particle size, BET specific surface area, main peak at 2θ = 29–30° and coefficient of thermal expansion were measured in the same manner as in Examples 1 and 2.

[0148] In addition, ceramic molded bodies were prepared by heating to 700°C over 3 hours and holding for 4 hours. The relationship between the thermal shrinkage rate (%) and temperature (°C) of the negative thermal expansion material sample used to evaluate the molded bodies was recorded together with the data. Figure 7 .

[0149] In addition, ceramic molded bodies were prepared by heating to 750°C over 3 hours and holding for 4 hours. The relationship between the thermal shrinkage rate (%) and temperature (°C) of the negative thermal expansion material sample used to evaluate the molded body was recorded together with the data. Figure 8 .

[0150] [Table 3] [Table 4] From Table 2, Table 4 and Figure 7 It can be seen that the negative thermal expansion material sample obtained in the examples has excellent negative thermal expansion characteristics. Compared with the negative thermal expansion material sample of Comparative Example 1, the coefficient of thermal expansion (α2) between 100 and 150°C is smaller than the coefficient of thermal expansion (α1) between 100 and 130°C. In the temperature range of 100 to 150°C, the volume reduction is gradual as the temperature rises.

[0151] In addition, by Figure 8 It can be seen that for ceramic molded bodies prepared by heating to 750°C in 3 hours and holding for 4 hours, compared with the case of the negative thermal expansion material sample of the comparative example, the volume reduction of the embodiment is gradual with the temperature rise in the temperature range of 100 to 150°C.

Claims

1. A negative thermal expansion material, characterized in that: It is a complex of zinc-phosphorus oxide and metal pyrophosphate. The zinc-phosphorus composite oxide comprises the zinc-phosphorus composite oxide represented by the following general formula (1): Zn x M y P z1 ABOUT t1 (1) In formula (1), M represents one or more elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho; x represents 0.0 < x ≤ 2.0; y represents 0.0 ≤ y < 2.0; z1 represents 1.7 ≤ z1 ≤ 2.3; and t1 represents 6.00 ≤ t1 ≤ 8.00, where 1.7 ≤ x + y ≤ 2.

3. The pyrophosphate metal salt comprises the pyrophosphate metal salt represented by the following general formula (2): THE w P z2 THE t2 (2) In formula (2), A represents one or more metallic elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy and Ho, w represents 1.7≤w≤2.3, z2 represents 1.7≤z2≤2.3, and t2 represents 6.00≤t2≤8.

00.

2. The negative thermal expansion material as described in claim 1, characterized in that: The composite has a core-shell structure, the core comprising a zinc-phosphorus composite oxide as shown in general formula (1), and the shell comprising a metal pyrophosphate salt as shown in general formula (2).

3. The negative thermal expansion material as described in claim 1 or 2, characterized in that: The zinc-phosphorus composite oxide represented by the general formula (1) is Zn2P2O7.

4. The negative thermal expansion material as described in claim 1 or 2, characterized in that: The pyrophosphate metal salts represented by the general formula (2) are Mn2P2O7 and Cu2P2O7.

5. The negative thermal expansion material as described in claim 1 or 2, characterized in that: The coefficient of thermal expansion between 80 and 200℃ is -23 × 10⁻⁶. -6 / K and below.

6. The negative thermal expansion material as described in claim 3, characterized in that: The ratio of the coefficient of thermal expansion α2 between 100 and 150°C to the coefficient of thermal expansion α1 between 100 and 130°C, α2 / α1, is less than 2.

5.

7. The negative thermal expansion material as described in claim 1 or 2, characterized in that: When using Cu-Kα as an X-ray source for X-ray diffraction measurements, the peak of the main peak was observed between 2θ and 30°, and between 2θ and 29.66° and 29.73°.

8. The negative thermal expansion material as described in claim 1 or 2, characterized in that: The average particle size is 0.1–100 μm.

9. The negative thermal expansion material as described in claim 1 or 2, characterized in that: The specific surface area of ​​BET is 0.05–50 m². 2 / g.

10. A method for manufacturing a negative thermal expansion material, characterized in that: A mixture comprising zinc-phosphorus composite oxide particles as shown in general formula (1) and a source A and a source P that are raw materials for generating metal pyrophosphate salts as shown in general formula (2) is calcined. Zn x M y P z1 ABOUT t1 (1) In formula (1), M represents one or more elements selected from Mg, Ca, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Na, K, F, Cl, Br, I, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, S, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy, and Ho; x represents 0 < x ≤ 2.0; y represents 0 ≤ y ≤ 2.0; z1 represents 1.7 ≤ z1 ≤ 2.3; and t1 represents 6.0 ≤ t1 ≤ 8.0, where 1.7 ≤ x + y ≤ 2.

3. THE w P z2 THE t2 (2) In formula (2), A represents one or more metallic elements selected from Mg, Cu, Fe, Cr, Mn, Ni, V, Li, Al, B, Sr, Ba, Ti, Zr, Hf, Nb, Ta, Y, Yb, Si, W, Mo, Co, Bi, Te, Pb, Ag, Cd, In, Sn, Sb, Te, Ga, Ge, La, Ce, Nd, Sm, Eu, Tb, Dy and Ho, w represents 1.7≤w≤2.3, z2 represents 1.7≤z2≤2.3, and t2 represents 6.0≤t2≤8.

0.

11. The method for manufacturing a negative thermal expansion material as described in claim 10, characterized in that: The zinc-phosphorus composite oxide represented by general formula (1) is obtained by calcining a reaction precursor containing at least zinc pyrophosphate.

12. A composite material, characterized in that: It includes the negative thermal expansion material and the positive thermal expansion material as described in claim 1 or 2.

13. The composite material as described in claim 12, characterized in that: The positive thermal expansion material is selected from at least one of metals, alloys, glass, ceramics, rubber, and resins.

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