Negative thermal expansion material, method for producing same, and composite material

Abstract

Provided is a negative thermal expansion material having excellent negative thermal expansion properties and exhibiting a gradual volume decrease with increasing temperature compared with the conventional zinc-phosphorus complex oxide Zn2P2O7 in a temperature range of 100-150°C.　 The negative thermal expansion material is characterized by comprising a zinc-phosphorus complex oxide represented by general formula (1). (1): ZnxCayMpPzOt (In the formula, M represents one or more metal elements selected from among Mg, Zn, 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; 0<x<2.00; 0<y<2.00; 0≤p≤1.00; 1.70≤z≤2.30; and 6.00≤t≤8.00, provided that 1.70≤x+y+p≤2.30)

Description

Negative thermal expansion material, its manufacturing method and composite material

[0001] The present invention relates to a negative thermal expansion material that contracts in response to a temperature rise, a method for producing the same, and a composite material containing the negative thermal expansion material.

[0002] Many substances increase in length and volume due to thermal expansion when the temperature rises. However, there are also known materials that exhibit negative thermal expansion, meaning that their volume decreases when heated (hereinafter referred to as "negative thermal expansion materials").

[0003] It is known that materials that exhibit negative thermal expansion can be used in conjunction with other materials to reduce the change in thermal expansion of the material with changes in temperature.

[0004] Examples of materials that exhibit negative thermal expansion include β-eucryptite and zirconium tungstate (ZrW ２ O ８ ), zirconium tungstate phosphate (Zr ２ WO ４ (P.O. ４ ) ２ ), Zn ｘ Cd １－ｘ (CN) ２ , manganese nitride, bismuth-nickel-iron oxide, etc. are known.

[0005] The linear expansion coefficient of zirconium tungstate phosphate is −3.4 to −3.0 ppm / °C in the temperature range of 0 to 400°C, and it is known to have a large negative thermal expansion. By using this zirconium tungstate phosphate in combination with a material that exhibits positive thermal expansion (hereinafter sometimes referred to as a "positive thermal expansion material"), a material with low thermal expansion can be produced (see Patent Documents 1 and 2, etc.). It has also been proposed to use a polymer compound such as a resin, which is a positive thermal expansion material, in combination with a negative thermal expansion material (see Patent Document 3, etc.).

[0006] In addition, Patent Document 3 discloses that Zn ２ P ２ O ７and negative thermal expansion materials in which part of the Zn in the zinc phosphorus composite oxide is substituted with 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, and Bi, or part of the P is substituted with at least one element selected from Al, Si, V, Ge, and Sn, have been proposed.

[0007] JP 2005-35840 A JP 2015-10006 A International Publication No. 2022 / 114004 Pamphlet

[0008] The zinc-phosphorus composite oxide of Patent Document 3 has advantages such as a smaller linear expansion coefficient than zirconium tungstate phosphate, can be produced using cheaper raw materials, can be produced industrially advantageously, and has excellent water resistance.

[0009] However, Zn ２ P ２ O ７ The zinc-phosphorus composite oxide undergoes a rapid volume reduction with increasing temperature, particularly in the temperature range of 100 to 150° C. Therefore, in a composite material containing a negative thermal expansion material and a positive thermal expansion material, the positive thermal expansion material cannot keep up with the rapid volume reduction of the negative thermal expansion material, and as a result, it becomes difficult to achieve a zero or low thermal expansion coefficient in the composite material containing the negative thermal expansion material.

[0010] Therefore, the present invention has negative thermal expansion and is superior to conventional Zn in the temperature range of 100 to 150°C. ２ P ２ O ７ The object of the present invention is to provide a negative thermal expansion material that exhibits a gradual volume decrease with increasing temperature compared to zinc-phosphorus composite oxide.

[0011] The present inventors have ２ P ２ O ７While investigating methods for improving the negative thermal expansion properties of the zinc phosphorus composite oxide described above, the inventors discovered that by incorporating Ca as a solid solution into the zinc phosphorus composite oxide, the resulting negative thermal expansion material has excellent negative thermal expansion properties and exhibits a more gradual volume decrease with increasing temperature in the temperature range of 100 to 150°C compared to conventional zinc phosphorus composite oxides, and have completed the present invention.

[0012] That is, the present invention (1) provides a compound represented by the following general formula (1): Zn ｘ Ca ｙ M ｐ P ｚ O ｔ (1) (In the formula, M represents one or more metal elements selected from Mg, Zn, 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<2.00; y represents 0<y<2.00; p represents 0≦p≦1.00; z represents 1.70≦z≦2.30; and t represents 6.00≦t≦8.00, provided that 1.70≦x+y+p≦2.30.) The present invention provides a negative thermal expansion material comprising a zinc-phosphorus composite oxide represented by the formula:

[0013] In addition, the present invention (2) has a thermal expansion coefficient of −10×10 between 80 and 200° C. －６ The present invention provides a negative thermal expansion material according to (1), characterized in that the thermal expansion coefficient is 0.1 / K or less.

[0014] The present invention (3) also provides a negative thermal expansion material according to (1) or (2), characterized in that the ratio (α2 / α1) of the thermal expansion coefficient (α2) between 100 and 150°C to the thermal expansion coefficient (α1) between 100 and 130°C is 3.0 or less.

[0015] The present invention (4) also provides the negative thermal expansion material according to (1) or (2), characterized in that the average particle size is 0.1 to 100 μm.

[0016] In addition, the present invention (5) is a method for producing a granular material having a BET specific surface area of ​​0.05 to 50 m ２The present invention provides a negative thermal expansion material according to any one of (1) to (4), characterized in that the thermal expansion coefficient is / g.

[0017] The present invention (6) also provides a method for producing a negative thermal expansion material according to any one of the present inventions (1) to (5), comprising: a first step of preparing a raw material mixture containing a Zn source, a Ca source, and a P source; and a second step of firing the raw material mixture to obtain the negative thermal expansion material.

[0018] The present invention (7) also provides a method for producing a negative thermal expansion material according to (6), characterized in that the raw material mixture contains at least zinc pyrophosphate hydrate, phosphoric acid, and a Ca source.

[0019] The present invention (8) also provides a composite material characterized by containing a negative thermal expansion material according to any one of the present inventions (1) to (5) and a positive thermal expansion material.

[0020] The present invention (9) also provides the composite material according to (8), wherein the positive thermal expansion material is at least one selected from metals, alloys, glasses, ceramics, rubbers, and resins.

[0021] According to the present invention, the negative thermal expansion coefficient is excellent, and the temperature range of 100 to 150°C is higher than that of conventional Zn. ２ P ２ O ７ It is possible to provide a negative thermal expansion material that exhibits a gradual volume decrease with increasing temperature compared to the zinc-phosphorus composite oxide.

[0022] 1 is an X-ray diffraction diagram of a negative thermal expansion material sample obtained in Example 2. 2 is an X-ray diffraction diagram of a negative thermal expansion material sample obtained in Comparative Example 1. 3 is an SEM photograph of a negative thermal expansion material sample obtained in Example 2. 4 is a diagram showing the relationship between the thermal shrinkage rate (%) and temperature (°C) of the ceramic molded bodies of the Examples and Comparative Examples.

[0023] The present invention will be described below based on preferred embodiments. The negative thermal expansion material of the present invention is a material represented by the following general formula (1): Zn ｘ Ca ｙ M ｐ P ｚ O ｔ(1) (In the formula, M represents one or more metal elements selected from Mg, Zn, 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<2.00; y represents 0<y<2.00; p represents 0≦p≦1.00; z represents 1.70≦z≦2.30; and t represents 6.00≦t≦8.00, provided that 1.70≦x+y+p≦2.30.) The zinc-phosphorus composite oxide is characterized by being composed of the zinc-phosphorus composite oxide represented by the formula:

[0024] In general formula (1), M represents an element optionally contained for the purpose of further adjusting the negative thermal expansion. M represents one or more elements selected from Mg, Zn, 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 general formula (1), x is 0<x<2.00. Regarding the lower limit of x, in order to improve the negative thermal expansion properties, x is preferably greater than 1.00, more preferably 1.10 or greater, more preferably 1.20 or greater, more preferably 1.50 or greater, more preferably 1.80 or greater, and more preferably 1.90 or greater. Regarding the upper limit of x, in order to improve the negative thermal expansion properties, x is preferably 1.999 or less, more preferably 1.995 or less, more preferably 1.990 or less, more preferably 1.970 or less, and more preferably 1.950 or less. The range of x can be a range combining the upper and lower limits. In general formula (1), y is 0<y<2.00. Regarding the lower limit of y, in order to exhibit a gradual volume decrease with increasing temperature in the temperature range of 100 to 150°C and to achieve excellent negative thermal expansion properties, y is preferably 0.001 or greater, more preferably 0.005 or greater, more preferably 0.010 or greater, more preferably 0.050 or greater, and more preferably greater than 0.050. Furthermore, with regard to the lower limit of y, from the viewpoint of exhibiting a gradual volume decrease with increasing temperature in the temperature range of 100 to 150°C and also having excellent negative thermal expansion properties, y is preferably less than 1.00, more preferably 0.90 or less, more preferably 0.80 or less, more preferably 0.50 or less, more preferably 0.30 or less, and more preferably 0.25 or less. The range of y can be a range combining the upper and lower limits. Furthermore, with regard to x / y, preferably x / y>1.0. In general formula (1), p satisfies 0≦p≦1.00. p satisfies 0≦p≦0.80. In general formula (1), z satisfies 1.70≦z≦2.30. z satisfies 1.80≦z≦2.20 in terms of further improving negative thermal expansion properties.In the general formula (1), t is 6.00≦t≦8.00. t is preferably 6.20≦t≦7.20, since the negative thermal expansion characteristics are further improved. However, x+y+p in the general formula (1) is 1.70≦x+y+p≦2.30. x+y+p is preferably 1.80≦x+y+p≦2.20, since the negative thermal expansion characteristics are further improved.

[0025] 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 m ２ / g, particularly preferably 0.10 to 10m ２ / g, more preferably 0.20 to 8 m ２ / g. When the BET specific surface area of ​​the negative thermal expansion material is within the above range, the negative thermal expansion material is easy to handle when used as a filler for resin, glass, etc. In the present invention, the BET specific surface area of ​​the negative thermal expansion material is a value measured by the BET single-point method using a fully automatic specific surface area measuring device Macsorb (manufactured by Mountec Co., Ltd.).

[0026] 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, and particularly preferably 0.2 to 80 μm, as determined by scanning electron microscopy. Having an average particle size within this range facilitates handling when used as a filler for resins, glass, etc. In the present invention, the average particle size of the negative thermal expansion material was determined by taking the arithmetic mean value of the particle sizes of 50 particles randomly selected at 1000x magnification during scanning electron microscopy. In this context, the particle size of each particle refers to the longest length (maximum length) of the line segments intersecting the two-dimensional projection image of the particle.

[0027] The particle shape of the negative thermal expansion material of the present invention is not particularly limited, and may be, for example, spherical, granular, plate-like, scale-like, whisker-like, rod-like, filament-like, or crushed.

[0028] The thermal expansion coefficient of the negative thermal expansion material of the present invention between 80 and 200°C is not limited as long as it is less than 0. However, the thermal expansion coefficient of the negative thermal expansion material of the present invention between 80 and 200°C is preferably less than -10 x 10 －６ / K or less, preferably -20×10－６ / K or less, and the lower limit is not particularly limited, but is generally −100×10 －６ / K or more, preferably -80 × 10 －６ In the negative thermal expansion material of the present invention, when combined with a positive thermal expansion material, the thermal expansion coefficient is more likely to offset the positive expansion. Therefore, the thermal expansion coefficient between 0 and 200°C is particularly preferably -10 x 10 －６ ~-100 x 10 －６ / K.

[0029] In the present invention, the thermal expansion coefficient between 80 and 200°C is determined by the following procedure. First, 0.05 g of propylene carbonate is added to 1.00 g of sample and pulverized and mixed in a mortar for 3 minutes. Then, 0.15 g is weighed out and the entire amount is filled into a φ6 mm mold. Next, a powder compact is produced by molding at a pressure of 0.5 tons using a hand press. The obtained powder compact is heated to 750°C in an electric furnace over 3 hours and held there for 4 hours to produce a ceramic compact. The thermal expansion coefficient of the produced ceramic compact is then measured using a thermomechanical measuring device (e.g., TMA4000SE manufactured by NETZSCH JAPAN). The measurement conditions are a nitrogen atmosphere, a load of 10 g, and a temperature range of 50°C to 225°C. The measurement is repeated twice within the temperature range of 50°C to 225°C, and the thermal expansion coefficient between 80 and 200°C from the second measurement is taken as the thermal expansion coefficient of the negative thermal expansion material.

[0030] Furthermore, the negative thermal expansion material according to the present invention has a volume reduction rate that is greater than that of conventional zinc-phosphorus composite oxides (Zn) at temperatures between 100 and 150°C. ２ P ２ O ７ ) is characterized by a gentler slope than that of conventional zinc-phosphorus composite oxides (Zn). ２ P ２ O ７), the ratio (α2 / α1) of the thermal expansion coefficient (α1) between 100 and 130°C to the thermal expansion coefficient (α2) between 100 and 150°C of the negative thermal expansion material of the present invention is 3.0 or less, preferably 0.5 to 3.0. A smaller ratio of α2 to α1 indicates a gradual volumetric decrease with increasing temperature in the temperature range of 100 to 150°C. Furthermore, the negative thermal expansion material of the present invention has an absolute difference of 40 or less between the thermal expansion coefficient (α1) between 100 and 130°C and the thermal expansion coefficient (α2) between 100 and 150°C, preferably 10 to 35, and more preferably 15 to 35. A smaller difference in the absolute values ​​of α1 and α2 indicates a gradual volumetric decrease with increasing temperature in the temperature range of 100 to 150°C.

[0031] In the present invention, the degree of volume loss with temperature increase between 100 and 150°C is determined by the following procedure. First, 0.05 g of propylene carbonate is added to 1.00 g of sample and pulverized and mixed in a mortar for 3 minutes. Then, 0.15 g is weighed out and the entire amount is filled into a φ6 mm mold. Next, a powder compact is produced by molding at a pressure of 0.5 tons using a hand press. The obtained powder compact is heated to 750°C in an electric furnace over 3 hours and held there for 4 hours to produce a ceramic compact. Next, the thermal expansion coefficient of the produced ceramic compact is measured using a thermomechanical measurement device (TMA4000SE manufactured by NETZSCH JAPAN). The measurement conditions are a nitrogen atmosphere, a load of 10 g, and a temperature range of 50°C to 225°C, with the measurement repeated twice. The degree of volume reduction with temperature increase is evaluated by calculating the ratio of the thermal expansion coefficient (α2) between 100 and 150°C to the thermal expansion coefficient (α1) between 100 and 130°C during the second cycle and the difference in absolute values ​​between α1 and α2.

[0032] The method for producing the negative thermal expansion material of the present invention is not particularly limited, but it can be produced industrially advantageously by carrying out the following first and second steps.

[0033] The method for producing a negative thermal expansion material of the present invention is characterized by comprising: a first step of preparing a raw material mixture containing a Zn source, a Ca source, and a P source; and a second step of sintering the raw material mixture to obtain a negative thermal expansion material.

[0034] The first step is to prepare a raw material mixture containing a Zn source, a Ca source, and a P source.

[0035] The Zn source in the first step is a compound having a Zn atom, and examples of the Zn source include zinc salts of organic carboxylic acids such as zinc gluconate, zinc citrate, zinc acetate, and zinc lactate, zinc salts of mineral acids, zinc oxide, zinc hydroxide, zinc phosphate, and zinc pyrophosphate.

[0036] The Ca source in the first step is a compound containing a Ca atom. Examples of the Ca source include calcium carbonate, oxide, hydroxide, halide, and carboxylate. Examples of calcium carboxylate include calcium gluconate, citrate, oxalate, acetate, and lactate.

[0037] The P source in the first step is a compound having a P atom. The P source is preferably phosphoric acid.

[0038] In the first step, in addition to the Zn source, Ca source, and P source, an M source may also be added as needed to prepare a raw material mixture containing the Zn source, Ca source, P source, and M source. M is one or more elements selected from Mg, Zn, 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. The M source in the first step is a compound containing an M atom. Examples of the M source include carbonates, oxides, hydroxides, halides, and carboxylates of M. Examples of the carboxylate of M include gluconate, citrate, oxalate, acetate, lactate, and the like.

[0039] It is preferable that the raw material mixture in the first step contains at least zinc pyrophosphate hydrate, phosphoric acid, and a Ca source, because it is easy to obtain a raw material mixture in which the raw materials are uniformly dispersed through an inexpensive and simple operation, and it is also easy to obtain a zinc-phosphorus composite oxide represented by general formula (1) that is single-phase in terms of X-ray diffraction by firing the obtained raw material mixture in the second step described below.

[0040] In the first step, it is preferable to appropriately adjust the amounts of the Zn source, Ca source, P source, and M source mixed so that the atomic molar ratio of Zn, Ca, P, and M in the raw material mixture satisfies the composition of the zinc-phosphorus composite oxide represented by the general formula (1). When zinc phosphate or zinc pyrophosphate is used as the Zn source, it is preferable to prepare the raw material mixture taking into consideration the amount of P atoms in the Zn source.

[0041] In the first step, a mixing treatment of a Zn source, a Ca source, a P source and an M source used as needed can be carried out by a wet method or a dry method.

[0042] When wet mixing is performed, it is preferable to obtain a raw material mixture by drying the entire amount to remove the solvent.

[0043] Alternatively, in the first step, a raw material mixture can be obtained by dissolving the Zn source, Ca source, P source, and an optional M source in an aqueous solvent, followed by removing the aqueous solvent. In this case, the Zn source, Ca source, P source, and optional M source can be soluble in an aqueous solvent. Examples of Zn sources soluble in an aqueous solvent include zinc salts of organic carboxylic acids and zinc salts of mineral acids. Examples of Ca sources soluble in an aqueous solvent include calcium salts, carbonates, and hydroxides of organic carboxylic acids. Examples of P sources soluble in an aqueous solvent include phosphoric acid. Examples of M sources soluble in an aqueous solvent include salts of organic carboxylic acids and salts of mineral acids of M.

[0044] In the first step, the composition of the zinc-phosphorus composite oxide represented by the general formula (1) obtained by drying the entire amount after the wet mixing treatment to remove the solvent is approximately equal to the atomic molar ratios of Zn, Ca, P, and M in the Zn source, Ca source, P source, and M source when the respective raw materials are charged.

[0045] The second step is a step of firing the raw material mixture prepared in the first step to obtain the negative thermal expansion material of the present invention.

[0046] The firing temperature in the second step is preferably 300 to 900°C, more preferably 500 to 800°C. On the other hand, if the firing temperature in the second step is below the above range, the production of the zinc-phosphorus composite oxide represented by the general formula (1) tends to be insufficient, and if it exceeds the above range, a solidified sintered body tends to be formed. The firing time in the second step is not particularly limited, and firing is carried out for a sufficient time until the negative thermal expansion material of the present invention is produced.

[0047] The production of the negative thermal expansion material of the present invention can be confirmed, for example, by determining whether a single-phase zinc-phosphorus composite oxide represented by general formula (1) is obtained by X-ray diffraction analysis.

[0048] In the second step, in many cases, the firing time is 0.5 hours or more, preferably 2 to 20 hours, and almost all of the raw material mixture becomes a negative thermal expansion material made of the zinc-phosphorus composite oxide represented by the general formula (1).

[0049] The firing atmosphere in the second step is not particularly limited, and may be any of an inert gas atmosphere, a vacuum atmosphere, an oxidizing gas atmosphere, and the air.

[0050] In the second step, the calcination may be carried out once or multiple times as desired. For example, in order to make the powder characteristics uniform, the calcined product may be pulverized and the pulverized product may be further calcined.

[0051] After firing, the material is cooled appropriately, and if necessary, crushed, crushed, classified, etc. to obtain the desired negative thermal expansion material.

[0052] The negative thermal expansion material made of zinc-phosphorus composite oxide represented by general formula (1) obtained by the method for producing a negative thermal expansion material of the present invention has an average particle size of preferably 0.1 to 100 μm, particularly preferably 0.2 to 80 μm, and even more preferably 0.2 to 20 μm, and a BET specific surface area of ​​0.05 to 50 m ２ / g, particularly preferably 0.10 to 10m ２ / g, more preferably 0.1 to 5 m２ It is preferable that the average particle size and / or BET specific surface area of ​​the negative thermal expansion material be within the above ranges, since this makes the negative thermal expansion material easy to handle when used as a filler for resin, glass, etc.

[0053] Furthermore, the particle surfaces of the negative thermal expansion material according to the present invention may be subjected to a surface treatment if necessary in order to improve the resin dispersibility and moisture resistance of the negative thermal expansion material. Furthermore, in the method for producing a negative thermal expansion material according to the present invention, the negative thermal expansion material obtained by carrying out the second step may be subjected to a surface treatment if necessary in order to improve the resin dispersibility and moisture resistance of the negative thermal expansion material.

[0054] Examples of surface treatments include methods of coating particle surfaces with inorganic compounds containing one or more elements selected from silane coupling agents, titanate coupling agents, fatty acids or derivatives thereof, Zn, Si, Al, Ba, Ca, Mg, Ti, V, Sn, Co, Fe, and Zr (see, for example, WO2020 / 095837, WO2020 / 261976, WO2019 / 087722, and JP-A-2020-147486). Surface treatments may also be performed by appropriately combining these.

[0055] The thermal expansion coefficient of the negative thermal expansion material obtained by the method for producing a negative thermal expansion material of the present invention between 80 and 200°C is -10 x 10 －６ / K or less, preferably -20×10 －６ / K or less, and the lower limit is not particularly limited, but is generally −100×10 －６ / K or more, preferably -80 × 10 －６ When the negative thermal expansion material of the present invention is combined with a positive thermal expansion material, the thermal expansion coefficient is particularly preferably −10×10 －６ ~-100 x 10 －６ / K.

[0056] Furthermore, the negative thermal expansion material obtained by the method for producing a negative thermal expansion material of the present invention has a ratio (α2 / α1) of the thermal expansion coefficient (α2) between 100 and 150°C to the thermal expansion coefficient (α1) between 100 and 130°C, which indicates the degree of volume reduction with temperature increase between 100 and 150°C, of ​​3.0 or less, preferably 0.5 to 3.0.

[0057] The negative thermal expansion material of the present invention is used as a powder or paste. When the negative thermal expansion material of the present invention is used as a 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 form of a 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 if necessary, a binder, a flux material, a dispersant, etc. may be added to use in the form of a paste.

[0058] The negative thermal expansion material of the present invention is used in combination with various organic or inorganic compounds as a positive thermal expansion material to form a composite material. The composite material of the present invention contains the negative thermal expansion material of the present invention and a positive thermal expansion material.

[0059] Organic compounds used as positive thermal expansion materials include, but are not limited to, rubber, polyolefin, polycycloolefin, polystyrene, ABS, polyacrylate, polyphenylene sulfide, phenolic resin, polyamide resin, polyimide resin, epoxy resin, silicone resin, polycarbonate resin, polyethylene resin, polypropylene resin, polyethylene terephthalate resin (PET resin), polyvinyl chloride resin, etc. Inorganic compounds used as positive thermal expansion materials include silicon dioxide, silicates, graphite, sapphire, various glass materials, concrete materials, various ceramic materials, etc.

[0060] Since the composite material of the present invention contains the negative thermal expansion material of the present invention, which has excellent negative thermal expansion properties, it is possible to achieve a negative thermal expansion coefficient, zero thermal expansion coefficient, or low thermal expansion coefficient depending on the blending ratio with other compounds.

[0061] The present invention will be described below with reference to examples, but the present invention is not limited to these. (X-ray Diffraction Apparatus) In the examples, an X-ray diffractometer (Ultima IV manufactured by Rigaku Corporation) was used to carry out measurements under the following measurement conditions: Radiation source: Cu-Kα Tube voltage: 40 kV Tube current: 40 mA Scanning speed: 4° / sec

[0062] Example 1 Zinc pyrophosphate trihydrate (Zn ２ P ２ O ７ ・3H ２ 3.498 g of calcium hydroxide (average particle size 1.2 μm), 0.037 g of calcium hydroxide (average particle size 2.1 μm), 0.0576 g of 85% phosphoric acid, and 10 mL of pure water were thoroughly ground and mixed in a mortar. The entire mixture was then dried at 130°C. The resulting dried powder was fired at 700°C for 4 hours. X-ray diffraction analysis of the fired powder revealed a single-phase α-Zn ２ P ２ O ７ This was a negative thermal expansion material sample (Zn １．９５ Ca ０．０５ P ２ O ７ )

[0063] Example 2 Zinc pyrophosphate trihydrate (Zn ２ P ２ O ７ ・3H ２ 3.408 g of calcium hydroxide (average particle size 1.2 μm), 0.074 g of calcium hydroxide (average particle size 2.1 μm), 0.115 g of 85% phosphoric acid, and 10 mL of pure water were thoroughly ground and mixed in a mortar. The entire mixture was then dried at 130°C. The resulting dried powder was fired at 700°C for 4 hours. X-ray diffraction analysis of the fired powder revealed a single-phase α-Zn ２ P ２ O ７ This was a negative thermal expansion material sample (Zn １．９０ Ca ０．１０ P ２ O ７ )

[0064] (Example 3) Zinc pyrophosphate trihydrate (Zn ２ P ２ O ７ ・3H ２3.229 g of calcium hydroxide (average particle size 1.2 μm), 0.148 g of calcium hydroxide (average particle size 2.1 μm), 0.231 g of 85% phosphoric acid, and 10 mL of pure water were thoroughly ground and mixed in a mortar. The mixture was then dried at 130°C. The resulting dried powder was fired at 700°C for 4 hours. X-ray diffraction analysis of the fired powder revealed a single-phase α-Zn ２ P ２ O ７ This was a negative thermal expansion material sample (Zn １．８０ Ca ０．２０ P ２ O ７ )

[0065] (Comparative Example 1) Zinc pyrophosphate trihydrate (Zn ２ P ２ O ７ ・3H ２ 3.400 g of ZnO and 10 mL of pure water were thoroughly ground and mixed in a mortar. The mixture was then dried at 130°C. The resulting dried powder was fired at 700°C for 4 hours. X-ray diffraction analysis of the fired powder revealed a single-phase α-Zn ２ P ２ O ７ This was a negative thermal expansion material sample (Zn ２ P ２ O ７ )

[0066] (Physical property evaluation) The average particle size, BET specific surface area, and thermal expansion coefficient were measured for the negative thermal expansion material samples obtained in the examples and comparative examples. The average particle size and thermal expansion coefficient were measured as follows. The results are shown in Table 1. An SEM photograph of the negative thermal expansion material sample obtained in Example 2 is shown in Figure 3.

[0067] (Average Particle Diameter) The average particle diameter of the negative thermal expansion material sample was determined by averaging the diameters of 50 particles randomly selected at a magnification of 1000 times under a scanning electron microscope.

[0068] [Measurement of Thermal Expansion Coefficient] (Preparation of Molded Body) 1.00 g of sample was mixed with 0.05 g of propylene carbonate in a mortar and ground for 3 minutes. Then, 0.15 g was weighed out and filled into a 6 mm diameter mold. A powder molded body was then produced by molding at 0.5 tonnes of pressure using a hand press. The resulting powder molded body was heated to 750°C in an electric furnace over 3 hours and held there for 4 hours to produce a ceramic molded body. The produced ceramic molded body was evaluated for its thermal expansion coefficient between 80 and 200°C and its degree of linear expansion with temperature increase between 100 and 150°C, as described below. (Measurement of Thermal Expansion Coefficient between 80 and 200°C) The thermal expansion coefficient of the produced ceramic molded body was measured using a thermomechanical measuring device (TMA4000SE, manufactured by NETZSCH JAPAN). The measurement conditions were a nitrogen atmosphere, a load of 10 g, and a temperature range of 50°C to 225°C, and the measurement was repeated twice. The thermal expansion coefficient between 80°C and 200°C in the second repeated measurement was taken as the thermal expansion coefficient of the negative thermal expansion material sample. The relationship between the thermal shrinkage rate (%) and temperature (°C) of the negative thermal expansion material sample is shown in Figure 4.

[0069] (Evaluation of the degree of volume reduction with temperature increase between 100 and 150°C) The thermal expansion coefficient of the produced ceramic molded body was measured using a thermomechanical measuring device (TMA4000SE manufactured by NETZSCH JAPAN). The measurement conditions were a nitrogen atmosphere, a load of 10 g, and a temperature range of 50°C to 225°C, and the measurement was repeated twice. The degree of volume reduction with temperature increase was evaluated by comparing the thermal expansion coefficient (α1) between 100 and 130°C in the second repeat with the thermal expansion coefficient (α2) between 100 and 150°C. A smaller ratio of α2 to α1 indicates a gradual volume reduction with temperature increase.

[0070]

[0071] From Table 1 and FIG. 4, it can be seen that the negative thermal expansion material samples obtained in the examples have a smaller ratio of the thermal expansion coefficient (α2) between 100 and 150°C to the thermal expansion coefficient (α1) between 100 and 130°C, and a smaller difference in the absolute values ​​of (α1) and (α2), compared to the negative thermal expansion material sample of Comparative Example 1, and that the volume decreases gradually with increasing temperature in the temperature range of 100 to 150°C.

Claims

1. The following general formula (1): Zn ｘ Ca ｙ M ｐ P ｚ O ｔ (1) (In the formula, M represents one or more elements selected from Mg, Zn, 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<2.00, y represents 0<y<2.00, p represents 0≦p≦1.00, z represents 1.70≦z≦2.30, and t represents 6.00≦t≦8.00, provided that 1.70≦x+y+p≦2.30.) A negative thermal expansion material comprising a zinc-phosphorus composite oxide represented by the formula:

2. The thermal expansion coefficient between 80 and 200°C is -10 x 10 －６ 2. The negative thermal expansion material according to claim 1, wherein the thermal expansion coefficient is 0.1 to 0.5 K.

3. A negative thermal expansion material as described in claim 1 or 2, characterized in that the ratio (α2 / α1) of the thermal expansion coefficient (α2) between 100 and 150°C to the thermal expansion coefficient (α1) between 100 and 130°C is 3.0 or less.

4. The negative thermal expansion material according to claim 1 or 2, characterized in that the average particle size is 0.1 to 100 μm.

5. BET specific surface area: 0.05 to 50 m ２ 3. The negative thermal expansion material according to claim 1, wherein the thermal expansion coefficient is 0.01 to 0.

5.

6. A method for producing a negative thermal expansion material according to claim 1, comprising: a first step of preparing a raw material mixture containing a Zn source, a Ca source, and a P source; and a second step of sintering the raw material mixture to obtain a negative thermal expansion material.

7. The method for producing a negative thermal expansion material according to claim 6, characterized in that the raw material mixture contains at least zinc pyrophosphate hydrate, phosphoric acid and a Ca source.

8. A composite material comprising the negative thermal expansion material according to claim 1 or 2 and a positive thermal expansion material.

9. The composite material according to claim 8, wherein the positive thermal expansion material is at least one material selected from the group consisting of metals, alloys, glass, ceramics, rubber and resins.