Zero-expansion material and method of making same

Abstract

The application provides a zero-expansion material with a chemical formula of Pb2CoMoO6 and using a Cu target K α1 X-ray powder diffraction pattern at room temperature expressed by a 2θ angle has diffraction peaks at 21.90°, 22.40°, 31.22°, 31.54° and 38.78°, and the measurement error of the 2θ angle is ±0.005°. The application further provides a method for preparing the zero-expansion material, which comprises the following steps: (1) grinding and mixing PbO, CoO and MoO3 in a protective gas environment to obtain a mixture; (2) after the mixture is sealed and wrapped, performing a heating and pressurizing treatment; (3) optionally, cooling and depressurizing the treatment product in the step (2). The application uses a high-temperature and high-pressure synthesis method to prepare a stable zero-expansion material Pb2CoMoO6 with zero-expansion performance in a wide temperature range of 120-300K containing room temperature. The zero-expansion material Pb2CoMoO6 has the advantages of small volume thermal expansion coefficient, zero-expansion performance in a wide temperature range of 120-300K containing room temperature and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of materials. Specifically, the present application relates to zero expansion materials and a preparation method thereof BACKGROUND

[0002] Thermal expansion behavior of materials has always been a hot and frontier issue in the field of materials science research, and is also an important factor that cannot be ignored in daily life and industrial production. In the early days, major accidents caused by neglecting the thermal expansion properties of materials or devices occurred frequently, and in recent years the development of high-precision devices also puts forward new requirements for the thermal expansion properties of materials.

[0003] It is generally believed that as the temperature rises (decreases), the volume of the material will expand (shrink) accordingly, i.e. thermal expansion and contraction. This thermal expansion and contraction characteristic comes from the anharmonic vibration between atoms inside the material. Negative thermal expansion materials exhibit exactly the opposite characteristics, i.e. the volume of the material shrinks (expands) as the temperature rises (decreases), and its thermal expansion coefficient is negative. More specifically, zero expansion materials have a thermal expansion coefficient very close to zero. It can be considered that the volume of zero expansion materials does not change as the temperature rises or decreases, so zero expansion materials have more profound physical connotations and broad application prospects.

[0004] Although zero expansion materials have been extensively studied in recent years, the known zero expansion materials are still very limited. And most of the existing zero expansion materials are obtained by compounding or solid solution means, so it is necessary to find a single-phase zero expansion material. In addition, in addition to the thermal expansion coefficient, another indicator for measuring the pros and cons of the zero expansion performance of a material is whether its zero expansion temperature interval can meet the needs of practical applications.

[0005] Some known zero expansion materials only have zero expansion characteristics at a lower temperature or in a very narrow temperature interval. For example: the classic zero expansion material Invar alloy Fe 0.65 Ni 0.35 only has zero expansion characteristics at 278-303K. Nanocrystalline Mn 3- x Cu 0.5 Ge 0.5 N only has zero expansion characteristics in the temperature interval of 12-230K. Zero expansion materials in the temperature interval near room temperature are even rarer.

[0006] Pb2CoMoO6 is a B-site Co 2+ ion and Mo 6+Ion-ordered perovskite materials derived from rock salt. Pb₂CoMoO₆ prepared under different temperatures and pressures exhibits different crystal structures. Taketoshi Fujita et al. reported that Pb₂CoMoO₆ prepared at 3.2 GPa and 1123 K has a tetragonal structure with the following cell parameters: (T. Fujita et al., Mater. Res. Bull. 1970, 5, 759). KPBurdina et al. reported that Pb₂CoMoO₆ prepared under conditions of 3.8 GPa and 1073 K had a tetragonal structure with the following cell parameters: (KP Burdina et al., AN SSSR, ser.fiz., 1975, 39, 1095).

[0007] There is an urgent need for a material that has zero expansion properties over a wide temperature range, including room temperature. Summary of the Invention

[0008] Therefore, an object of the present invention is to provide a zero-expansion material that exhibits zero expansion properties over a wide temperature range of 120-300 K, including room temperature. Another object of the present invention is to provide a method for preparing the zero-expansion material of the present invention.

[0009] The above-mentioned objective of the present invention is achieved through the following technical solution.

[0010] In the context of this invention, the term "room temperature" refers to its conventional meaning in the art, approximately 300K.

[0011] On one hand, the present invention provides a zero-expansion material with the chemical formula Pb₂CoMoO₆, and uses a Cu target K α1 The diffraction pattern of the X-ray powder at 300K, expressed in 2θ angles, shows diffraction peaks at 21.90°, 22.40°, 31.22°, 31.54°, and 38.78°, with a 2θ angle measurement error of ±0.005°.

[0012] Preferably, in the zero-expansion material of the present invention, the space group of the zero-expansion material at room temperature is orthogonal Pnma, and the lattice constants a, b, and c are respectively... and

[0013] Preferably, in the zero-expansion material described in this invention, a Cu target K is used. α1X-ray powder diffraction pattern at room temperature expressed in 2θ angle has diffraction peaks at 44.72°, 45.78°, 55.84°, 56.44°, 65.94°, the measurement error of 2θ angle is ±0.005°.

[0014] Preferably, in the zero expansion material according to the present application, the volume thermal expansion coefficient of the zero expansion material is 1.21×10-6-1.21×10-5 in the temperature range of 120-300K. -6 K -1 .

[0015] In another aspect, the present application provides a method for preparing the zero expansion material according to the present application, comprising the following steps:

[0016] (1) grinding and mixing PbO, CoO and MoO3 in a protective gas environment to obtain a mixture;

[0017] (2) after the mixture is sealed and wrapped, performing a heating and pressurizing treatment;

[0018] (3) optionally, cooling and depressurizing the treatment product in step (2).

[0019] The inventors of the present application unexpectedly found that by the high temperature and high pressure synthesis method according to the present application, a new crystal form of Pb2CoMoO6 can be prepared, and the new crystal form has zero expansion performance in a wide temperature range of 120-300K including room temperature.

[0020] Preferably, in the method according to the present application, the molar ratio of PbO, CoO and MoO3 in step (1) is PbO:CoO:MoO3=2:1:1.

[0021] Preferably, in the method according to the present application, the protective gas is one or more of nitrogen, helium and argon.

[0022] Preferably, in the method according to the present application, the grinding in step (1) is performed by grinding in an agate mortar for 15 minutes to 2 hours.

[0023] Preferably, in the method according to the present application, the sealing and wrapping in step (2) is performed by using a gold capsule or a platinum-gold capsule.

[0024] Preferably, in the method according to the present application, the gold capsule or the platinum-gold capsule is cylindrical.

[0025] Preferably, in the method according to the present application, the gold capsule or the platinum-gold capsule has a diameter of 2-10mm, a height of 2-10mm and a thickness of 0.1-1mm.

[0026] Preferably, in the method of the present application, the treatment in step (2) is carried out at a temperature of 1173-1473K, a pressure of 5-10 GPa, and a time of 10 minutes or more, more preferably 10-60 minutes.

[0027] Preferably, in the method of the present application, the treatment in step (2) is carried out in a cubic anvil press or a 6-8 type two-stage push press.

[0028] Preferably, in the method of the present application, the cooling in step (3) refers to cooling the product to room temperature in 30 seconds or less or in 1-10 hours.

[0029] Preferably, in the method of the present application, the pressure reduction in step (3) refers to reducing the product to ambient pressure in 5-24 hours.

[0030] The present application has the following beneficial effects:

[0031] The present application uses a high-temperature and high-pressure synthesis method to prepare a stable zero-expansion material Pb2CoMoO6 with zero-expansion properties in a wide temperature range of 120-300K including room temperature. The zero-expansion material Pb2CoMoO6 provided by the present application has a small volume thermal expansion coefficient and zero-expansion properties in a wide temperature range of 120-300K including room temperature. The zero-expansion material Pb2CoMoO6 of the present application has potential application value in future high-precision electronic devices and thermoelectric materials. BRIEF DESCRIPTION OF DRAWINGS

[0032] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings, in which:

[0033] Figure 1 XRD pattern of the zero-expansion material Pb2CoMoO6 of Example 1 of the present application at 300K;

[0034] Figure 2 Temperature-dependent XRD pattern of the zero-expansion material Pb2CoMoO6 of Example 1 of the present application;

[0035] Figure 3 Temperature-dependent lattice constant curve of the zero-expansion material Pb2CoMoO6 of Example 1 of the present application;

[0036] Figure 4 Temperature-dependent volume curve of the zero-expansion material Pb2CoMoO6 of Example 1 of the present application. DETAILED DESCRIPTION

[0037] The application will be further described in conjunction with the specific embodiments below, and the examples given are only for the purpose of illustrating the application, but not for limiting the scope of the application.

[0038] Example 1

[0039] PbO (purity > 99.9%), CoO (purity > 99.9%), and MoO3 (purity > 99.9%) were mixed in a molar ratio of 2:1:1, and were ground in a corundum mortar for 30 minutes in an argon-filled glove box to make them fully mixed and uniform, to obtain a mixture. The mixture was filled into a gold capsule with a diameter of 3 mm, a height of 5 mm, and a thickness of 0.1 mm, and was sealed. The obtained gold capsule was placed in a cubic press. The raw materials in the gold capsule were allowed to react under a pressure of 6 GPa and a temperature of 1273 K for 10 minutes, to obtain a reaction product. The reaction product was cooled to room temperature in 30 seconds, and the pressure was slowly released for 5 hours. Finally, the reaction product was taken out of the gold capsule, to obtain Pb2CoMoO6.

[0040] Performance measurement

[0041] 1. XRD test

[0042] A SmartLab X-ray diffractometer produced by Japan Rigaku Company was used to characterize the structure of the zero expansion material. The target for generating X-rays was a copper target, Cu-K α1 The wavelength was 0.15046 nm, and the test was performed under normal pressure, with a diffraction angle 2θ ranging from 10 to 100°.

[0043] Figure 1 XRD pattern of Pb2CoMoO6 prepared in Example 1 of the application at 300 K. Through Figure 1 the positions and intensities of the diffraction peaks in the pattern, it can be concluded that Pb2CoMoO6 prepared in Example 1 of the application is of an orthorhombic crystal system, with a space group of Pnma, and the lattice constants a, b, and c are 0.546 nm, 0.546 nm, and 1.123 nm, respectively. and The zero expansion material Pb2CoMoO6 of the application uses a Cu target K α1 diffraction, and its X-ray powder diffraction pattern at 300 K expressed in terms of 2θ angle has diffraction peaks at 21.90°, 22.40°, 31.22°, 31.54°, 38.78°, 44.72°, 45.78°, 55.84°, 56.44°, and 65.94°, with a measurement error of ±0.005° in terms of 2θ angle.

[0044] Figure 2 Temperature-dependent XRD pattern of Pb2CoMoO6 prepared in Example 1 of the application. The temperature test range was 120-500 K. Through Figure 2The positions and intensities of each diffraction peak can be obtained, and Pb2CoMoO6 undergoes a first-order structural phase transition as the temperature increases, and the space group changes from Pnma of the orthorhombic system to Fm-3m of the cubic system.

[0045] 2. Rietveld refinement of XRD patterns

[0046] The lattice constants and volumes of the zero-expansion material were obtained by Rietveld refinement of the XRD pattern of Pb2CoMoO6 of Example 1 using the GSAS program.

[0047] Figure 3 The curve of the lattice constant of Pb2CoMoO6 prepared in Example 1 of the present application versus temperature. The lattice constant of Pb2CoMoO6 prepared in Example 1 of the present application versus temperature was obtained by Rietveld refinement of the XRD pattern of Pb2CoMoO6 using the GSAS program. Figure 3 The change of the lattice constant with temperature can be seen from the change of the lattice constant of the orthorhombic system Pb2CoMoO6 with temperature, and the lattice constant a of the orthorhombic system Pb2CoMoO6 increases first and then decreases with the increase of temperature, and reaches a peak at 300K. P The lattice constant c decreases with the increase of temperature, and the lattice constant b increases with the increase of temperature. The lattice constant a of the high-temperature cubic system Pb2CoMoO6 increases with the increase of temperature. P P The lattice constant c decreases with the increase of temperature, and the lattice constant b increases with the increase of temperature. The lattice constant a of the high-temperature cubic system Pb2CoMoO6 increases with the increase of temperature. F

[0048] Figure 4 The curve of the volume of Pb2CoMoO6 prepared in Example 1 of the present application versus temperature. The volume of Pb2CoMoO6 prepared in Example 1 of the present application versus temperature was obtained by Rietveld refinement of the XRD pattern of Pb2CoMoO6 using the GSAS program. Figure 4 The change of the lattice constant with temperature can be seen from the change of the lattice constant of the orthorhombic system Pb2CoMoO6 with temperature, and the lattice constant a of the orthorhombic system Pb2CoMoO6 increases first and then decreases with the increase of temperature, and reaches a peak at 300K. -6 K -1 , Pb2CoMoO6 exhibits obvious zero-expansion performance in the wide temperature range of 120-300K including room temperature. In the temperature range of 300-380K, Pb2CoMoO6 exhibits negative thermal expansion characteristics. In the temperature range of 380-410K, Pb2CoMoO6 exhibits a huge volume shrinkage, and the volume shrinkage amount is -0.23%.

[0049] Example 2

[0050] ​​PbO (purity > 99.9%), CoO (purity > 99.9%), MoO3 (purity > 99.9%) were mixed in a molar ratio of 2:1:1, and ground in a corundum mortar for 1 hour in an argon-filled glove box to mix them sufficiently and uniformly, to obtain a mixture. The mixture was filled into a gold capsule with a diameter of 3 mm, a height of 4.5 mm, and a thickness of 0.1 mm, and sealed. The obtained gold capsule was placed in a cubic press. The raw materials in the gold capsule were allowed to react under conditions of a pressure of 5 GPa and a temperature of 1323 K for 30 minutes, to obtain a reaction product. The reaction product was cooled to room temperature in 30 seconds, and the pressure was slowly released over 6 hours. Finally, the reaction product was taken out of the gold capsule, to obtain Pb2CoMoO6.

[0051] The room-temperature zero expansion material Pb2CoMoO6 prepared in this example had the same structure as in Example 1.

[0052] Example 3

[0053] PbO (purity > 99.9%), CoO (purity > 99.9%), MoO3 (purity > 99.9%) were mixed in a molar ratio of 2:1:1, and ground in a corundum mortar for 2 hours in an argon-filled glove box to mix them sufficiently and uniformly, to obtain a mixture. The mixture was filled into a platinum capsule with a diameter of 3 mm, a height of 5.5 mm, and a thickness of 0.1 mm, and sealed. The obtained platinum capsule was placed in a cubic press. The raw materials in the platinum capsule were allowed to react under conditions of a pressure of 9 GPa and a temperature of 1373 K for 1 hour, to obtain a reaction product. The reaction product was cooled to room temperature in 30 seconds, and the pressure was slowly released over 8 hours. Finally, the reaction product was taken out of the platinum capsule, to obtain Pb2CoMoO6.

[0054] The room-temperature zero expansion material Pb2CoMoO6 prepared in this example had the same structure as in Example 1.

Claims

1. A zero-expansion material having the chemical formula Pb2CoMoO6 and using a Cu target K α1 diffraction, the X-ray powder diffraction pattern at room temperature expressed in terms of 2θ angle has diffraction peaks at 21.90°, 22.40°, 31.22°, 31.54°, 38.78°, 44.72°, 45.78°, 55.84°, 56.44°, 65.94°, with a measurement error of ±0.005° in the 2θ angle; The zero-expansion material is prepared by a method comprising the following steps: (1) grinding and mixing PbO, CoO and MoO3 in a protective gas environment to obtain a mixture; (2) after sealing the mixture, performing a heating and pressurizing treatment; (3) optionally, cooling and depressurizing the product of step (2); The treatment in step (2) is performed under the following conditions: temperature is 1173-1473 K, pressure is 5-10 GPa, and time is more than 10 minutes.

2. The zero expansion material of claim 1, wherein, The space group of the zero-expansion material at room temperature is orthorhombic Pnma, and the lattice constants a, b and c are 11.4618 Å, 7.9085 Å and 5.7112 Å, respectively.

3. The zero expansion material of claim 1, wherein, The volume thermal expansion coefficient of the zero-expansion material is 1.21 x 10 -6 K -1 .

4. The zero expansion material of claim 1, wherein, The molar ratio of PbO, CoO and MoO3 in step (1) is PbO:CoO:MoO3=2:1:

1.

5. The zero expansion material of claim 1, wherein, The protective gas is one or more of nitrogen, helium and argon.

6. The zero expansion material of claim 1, wherein, The grinding in step (1) is performed by grinding in an agate mortar for 15 minutes to 2 hours.

7. The zero expansion material of claim 1, wherein, The sealing in step (2) is performed by using a gold capsule or a platinum-gold capsule.

8. The zero expansion material of claim 7, wherein, The gold capsule or the platinum-gold capsule is cylindrical.

9. The zero expansion material of claim 8, wherein, The diameter of the gold capsule or the platinum-gold capsule is 2-10 mm, the height is 2-10 mm, and the thickness is 0.1-1 mm.

10. The zero expansion material of claim 1, wherein, The treatment in step (2) is performed for 10-60 minutes.

11. The zero expansion material of claim 1, wherein, The treatment in step (2) is performed in a hexagonal top press or a 6-8 type secondary push press.

12. The zero expansion material of claim 1, wherein, The cooling in step (3) refers to cooling the product to room temperature within less than or equal to 30 seconds or within 1-10 hours.

13. The zero expansion material of claim 1, wherein, The depressurization in step (3) refers to depressurizing the product to ambient pressure within 5-24 hours.

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