A negative thermal expansion coefficient material TaM IV (PO4)3 and a preparation method thereof

Abstract

This invention belongs to the field of thermal expansion materials, and discloses a material with a negative coefficient of thermal expansion, TaM. IV (PO4)3 and its preparation method. M IV =Zr or Hf. (1) According to the target product TaM IV (PO4)3 stoichiometric molar ratio Ta∶M IV ∶P=1∶1∶3, weigh out raw materials Ta2O5 and M IV O2, NH4H2PO4, then add Ta2O5, M IV The total mass of O2, NH4H2PO4, and V2O5 is 3~12 wt.% and ground until uniformly mixed. The resulting mixed powder is sintered at 500~700℃ for 6~10 h; (2) The sintered product obtained in step (1) is ground into powder, then pressed into tablets and sintered at 1200~1300℃ for 6~24 h. After cooling to room temperature, the target product TaM is obtained. IV (PO4)3. This invention discovers a new NZP material, TaM. IV (PO4)3, through thermal expansion tests on these materials, it was found that the present invention TaM IV (PO4)3 series materials have negative thermal expansion properties, and their synthesis process is simple, reliable, and highly reproducible.

Description

Technical Field

[0001] This invention belongs to the field of thermal expansion materials, specifically relating to a material with a negative coefficient of thermal expansion, TaM. IV (PO4)3 and its preparation method. Background Technology

[0002] Traditional materials typically expand when heated and contract when cooled. However, in certain applications, especially those requiring high stability and precision, this thermal expansion behavior can cause problems. For example, in the manufacture of optical components, thermal expansion can lead to changes in the optical path, degrading device performance. In the aerospace field, extreme temperature changes can damage equipment such as satellites and telescopes. Therefore, a material or technology is needed that can achieve negative thermal expansion under temperature changes to address these challenges. A class of materials with anomalous thermal expansion properties, whose dimensions decrease with increasing temperature, is called negative thermal expansion (NTE) materials. Since the discovery of ZrW₂O₈, the development of NTE materials has become an increasingly interesting area in science and technology. Combining NTE ceramics with positive thermal expansion materials to prepare zero or low thermal expansion materials is of great significance. Furthermore, these materials play an important role in improving the performance of precision devices, such as thermal stability, thermal shock resistance, thermal conductivity, radiation resistance, and structural stability.

[0003] Since the beginning of the 21st century, aerospace, precision instruments, and microelectronics have experienced rapid development. However, the thermal stress caused by the mismatch in thermal expansion coefficients has, to some extent, constrained the development of these fields. Currently, traditional materials, including metals, plastics, and ceramics, expand when heated. Although some complex mechanical designs have been proposed to compensate for the thermal expansion of these materials, these solutions are often complex, expensive, and difficult to implement. Therefore, it is necessary to develop a new material or technology that can overcome the adverse effects of traditional materials under temperature changes. Combining negative thermal expansion materials with commonly used materials is an effective method for preparing low thermal expansion materials, but residual thermal stress exists at the phase interfaces of different phases in composite materials, which affects the performance and lifespan of the materials. Preparing high-performance single-phase low thermal expansion materials is a more direct and effective means to solve the above problems. To fundamentally solve the series of problems caused by thermal expansion, two solutions can be chosen: one is to combine negative and positive thermal expansion materials to design near-zero expansion materials, and the other is to directly synthesize near-zero expansion materials. In recent years, the sodium zirconium phosphate (NZP) family has attracted widespread attention due to its very low coefficient of thermal expansion, high thermal and chemical stability, fast ionic conductivity, and flexibility in ion substitution. NZP ceramics have potential applications in telescope technology, the automotive industry, gas sensors, and aerospace. The excellent properties of the NZP family are mainly attributed to its flexible crystal structure. Its crystal structure consists of PO4 tetrahedra and ZrO6 octahedra sharing a common vertex, forming a stable three-dimensional framework structure. Many voids exist within this three-dimensional framework, which can be occupied by ions such as lithium, sodium, potassium, rubidium, cesium, calcium, strontium, and barium. The occupancy of these voids by different ions has a significant impact on the material's thermal expansion properties. Many materials in the NZP family exhibit negative or near-zero thermal expansion, such as CsZr2(PO4)3(α-ZrO2)2(PO4 ... av =(-0.22×10 -6 K -1 ), Sr 0.5 Hf2(PO4)3 (α av =1.66×10 -6 K -1 NZP series materials are not only easy to synthesize, but also have a wide temperature range, making them promising for applications. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the present invention aims to provide a material with a negative thermal expansion coefficient, TaM. IV (PO4)3 and its preparation method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] TaM, a material with a negative coefficient of thermal expansionIV (PO4)3, M IV =Zr or Hf.

[0007] Preferably, the negative thermal expansion material is TaZr(PO4)3 or TaHf(PO4)3, and the space group is hexagonal.

[0008] The negative thermal expansion coefficient material TaM IV The preparation method of (PO4)3 is as follows:

[0009] (1) According to the target product TaM IV The stoichiometric molar ratio of (PO4)3, Ta:M IV ∶P=1∶1∶3, weigh out raw materials Ta2O5 and M IV O2, NH4H2PO4, then add Ta2O5, M IV The total mass of O2, NH4H2PO4 and V2O5 is 3~12 wt.% and ground until uniformly mixed. The resulting mixed powder is sintered at 500~700 ℃ for 6~10 h.

[0010] (2) Grind the sintered product obtained in step (1) into powder, then press it into tablets and sinter it at 1200~1300℃ for 6~24 h. After cooling to room temperature, the target product TaM is obtained. IV (PO4)3.

[0011] Preferably, in step (1), the amount of V2O5 added accounts for 8~12 wt.% of the total mass of the three raw materials Ta2O5, HfO2 and NH4H2PO4.

[0012] Preferably, in step (1), wet grinding is used, and ethanol is added during grinding, the amount added being enough to wet Ta2O5, NH4H2PO4, and M. IV Based on O2 and V2O5.

[0013] Preferably, in steps (1) and (2), the temperature is increased to the sintering temperature at a heating rate of 1~5 °C / min.

[0014] The present invention involves sintering in two stages. One purpose is to release ammonia from NH4H2PO4, and the other is to make the synthesized sample more compact. V2O5 is a sintering aid. Adding V2O5 can suppress the formation of TaPO5 impurities. Furthermore, V2O5 will volatilize violently above 700℃, and the product will not contain V2O5.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) A new NZP material, TaM, was discovered. IV(PO4)3, through thermal expansion tests on these materials, it was found that the present invention TaM IV (PO4)3 series materials have negative thermal expansion properties, and their synthesis process is simple, reliable, and highly reproducible;

[0017] (2) TaM IV (PO4)3 series materials can be combined with positive thermal expansion materials to produce zero thermal expansion materials, which are expected to be applied in high-tech fields such as biomedical materials, aerospace equipment, and precision instruments. Attached Figure Description

[0018] Figure 1 XRD patterns of TaZr(PO4)3 and TaHf(PO4)3 prepared in Examples 1-2 compared with standard PDF cards.

[0019] Figure 2 XRD patterns of TaHf(PO4)3 prepared in Comparative Examples 1-3 and Examples 2-3 compared with standard PDF cards.

[0020] Figure 3 Curves showing the relative lengths of TaZr(PO4)3 and TaHf(PO4)3 prepared in Examples 1 and 2 as a function of temperature. Detailed Implementation

[0021] To make the present invention clearer and more explicit, the present invention will be further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0022] Example 1

[0023] The preparation method of TaZr(PO4)3 negative thermal expansion material includes the following steps: Selecting analytically pure tantalum pentoxide (Ta2O5), zirconium dioxide (ZrO2), and ammonium dihydrogen phosphate (NH4H2PO4) as raw materials, mixing Ta2O5, ZrO2, and NH4H2PO4 in a molar ratio of Ta∶Zr∶P = 1∶1∶3, then adding vanadium pentoxide (V2O5) accounting for 8 wt.% of the total mass of Ta2O5, ZrO2, and NH4H2PO4, followed by wetting with anhydrous ethanol and grinding in an agate mortar for 2 h. The resulting mixed powder is heated to 600 °C in a muffle furnace at a heating rate of 5 °C / min and sintered for 6 h. The sintered product is ground for 30 min and pressed into sheets with a diameter of 8 mm and a height of 5 mm. These sheets are then heated to 1300 °C in a muffle furnace at a heating rate of 5 °C / min and sintered for 6 h. h, naturally cooled to room temperature in the air, yielding TaZr(PO4)3.

[0024] Example 2

[0025] The preparation method of TaHf(PO4)3 negative thermal expansion material includes the following steps: Selecting analytically pure tantalum pentoxide (Ta2O5), hafnium dioxide (HfO2), and ammonium dihydrogen phosphate (NH4H2PO4) as raw materials, mixing Ta2O5, HfO2, and NH4H2PO4 in a molar ratio of Ta:Hf:P = 1:1:3, then adding vanadium pentoxide (V2O5) accounting for 8 wt.% of the total mass of Ta2O5, HfO2, and NH4H2PO4, followed by wetting with anhydrous ethanol and grinding in an agate mortar for 2 h. The resulting mixed powder is heated to 600 ℃ in a muffle furnace at a heating rate of 5 ℃ / min and sintered for 6 h. The sintered product is ground for 30 min and pressed into sheets with a diameter of 8 mm and a height of 5 mm. The sheets are then heated to 1200 ℃ in a muffle furnace at a heating rate of 5 ℃ / min and sintered for 6 h. h, naturally cooled to room temperature in the air, yielding TaHf(PO4)3.

[0026] Example 3

[0027] The preparation method of TaHf(PO4)3 negative thermal expansion material differs from that of Example 2 in that the amount of vanadium pentoxide (V2O5) added accounts for 12 wt.% of the total mass of the three raw materials Ta2O5, HfO2 and NH4H2PO4; all other aspects are the same as in Example 2.

[0028] Compare with Example 1

[0029] The preparation method of TaHf(PO4)3 negative thermal expansion material differs from that of Example 2 in that: the amount of vanadium pentoxide (V2O5) added accounts for 0 wt.% of the total mass of the three raw materials Ta2O5, HfO2 and NH4H2PO4; all other aspects are the same as in Example 2.

[0030] Compare with Example 2

[0031] The preparation method of TaHf(PO4)3 negative thermal expansion material differs from that of Example 2 in that: the amount of vanadium pentoxide (V2O5) added accounts for 4 wt.% of the total mass of the three raw materials Ta2O5, HfO2 and NH4H2PO4; all other aspects are the same as in Example 2.

[0032] Compare with Example 3

[0033] The preparation method of TaHf(PO4)3 negative thermal expansion material differs from that of Example 2 in that: the amount of vanadium pentoxide (V2O5) added accounts for 16 wt.% of the total mass of the three raw materials Ta2O5, HfO2 and NH4H2PO4; all other aspects are the same as in Example 2.

[0034] Product characterization and performance testing

[0035] The XRD patterns of TaZr(PO4)3 and TaHf(PO4)3 prepared in Examples 1 and 2 are compared with those of the standard PDF card as shown below. Figure 1 As shown, the diffraction peaks of TaZr(PO4)3 and TaHf(PO4)3 are consistent with those of PDF card 04-017-4646 (TaTi(PO4)3), indicating that TaZr(PO4)3 and TaHf(PO4)3 were successfully synthesized. Rietveld refinement reveals that the TaZr(PO4)3 prepared in Example 1 has lattice parameters a=b=8.758 Å and c=22.502 Å at room temperature, with space group R-3c, belonging to the hexagonal crystal system; the TaHf(PO4)3 prepared in Example 2 has lattice parameters a=b=8.734 Å and c=22.426 Å at room temperature, with space group R-3c, also belonging to the hexagonal crystal system.

[0036] The XRD patterns of TaHf(PO4)3 prepared in Examples 1-3 and Examples 2-3 compared with the standard PDF card are shown below. Figure 2 As shown, TaHf(PO4)3 (0 wt.% V2O5) was prepared in Control Example 1, TaHf(PO4)3 (4 wt.% V2O5) was prepared in Control Example 2, TaHf(PO4)3 (8 wt.% V2O5) was prepared in Example 2, TaHf(PO4)3 (12 wt.% V2O5) was prepared in Example 3, and TaHf(PO4)3 (16 wt.% V2O5) was prepared in Control Example 3. As can be seen, high-intensity TaPO5 impurity peaks appear in TaHf(PO4)3 (0 wt.% V2O5) and TaHf(PO4)3 (4 wt.% V2O5). Furthermore, the intensity of the TaPO5 peaks gradually decreases with increasing V2O5 content. When the V2O5 content is 8 wt.%, TaPO5 almost completely disappears. When the V2O5 content is 12 wt.%, the diffraction peaks are basically consistent with those at 8 wt.%. When the V2O5 content is 16 wt.%, many impurities appear. This indicates that V2O5, as a sintering aid, can effectively suppress the formation of TaPO5 impurities within a reasonable addition range. The absence of detected V2O5 peaks indicates that the V2O5 has completely volatilized. The optimal addition amount of V2O5 is between 8% and 12%, as excessive V2O5 will produce impurities.

[0037] The curves showing the relative lengths of TaZr(PO4)3 and TaHf(PO4)3 prepared in Examples 1 and 2 as a function of temperature are shown below. Figure 3 As shown. The calculated thermal expansion coefficient of TaZr(PO4)3 is -2.02 × 10⁻⁶. -6 K -1 (300~670K); The coefficient of thermal expansion of TaHf(PO4)3 is -2.22×10⁻⁶.-6 K -1 (300~670K).

[0038] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A material with negative thermal expansion coefficient TaM IV (PO4)3, characterized in that: M IV = Hf.

2. The negative thermal expansion material TaM IV (PO4)3 as claimed in claim 1, characterized in that: The negative thermal expansion coefficient material is TaHf(PO4)3, and the space group is hexagonal. ​ 3. A negative thermal expansion material TaM according to claim 1 or 2 IV A method for producing a negative thermal expansion material TaM (PO4)3, characterized by, The preparation steps are as follows: (1) According to the stoichiometric molar ratio Ta:M:P=1:1:3 of the target product TaM(PO4)3, weigh the raw materials Ta2O5, M IV O2, NH4H2PO4, and then add 8~12 wt.% of V2O5 based on the total mass of Ta2O5, M IV O2 and NH4H2PO4, grind until mixed uniformly, and sinter the obtained mixed powder at 500~700 ℃ for 6~10 h; IV O2 and NH4H2PO4, grind until mixed uniformly, and sinter the obtained mixed powder at 500~700 ℃ for 6~10 h; IV O2 and NH4H2PO4, grind until mixed uniformly, and sinter the obtained mixed powder at 500~700 ℃ for 6~10 h; (2), grinding the sintered product obtained in step (1) into powder, then tabletting and sintering at 1200-1300 °C for 6-24 h, and after cooling to room temperature, obtaining the target product TaM IV (PO4)3.

4. The negative thermal expansion material TaM of claim 3 IV A method for producing a material of negative thermal expansion coefficient TaM(PO4)3, characterized by: In step (1), wet grinding is used, and ethanol is added during grinding. The amount of ethanol added is such that Ta2O5, NH4H2PO4, M IV O2, and V2O5are moistened.

5. A negative thermal expansion material TTaM of claim 3 IV A method for producing a material of formula TTaM(PO4)3, characterized in that: In steps (1) and (2), the temperature is raised to the sintering temperature at a temperature raising rate of 1-5 ℃ / min.

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