HIGH-ENTROPY RARE EARTH-TOUGHENED TANTALATE CERAMIC AND PREPARATION METHOD THEREFOR

Abstract

The present disclosure provides a high-entropy rare earth-toughened tantalate ceramic. The ceramic is prepared by sintering Ta.sub.2O.sub.5 powder and x types of different RE.sub.2O.sub.3 powder, 4≤x≤9, and the molar ratio of the RE.sub.2O.sub.3 powders is 1. RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder having the molar ratio of RE to Ta being 1:1 are weighed, a solvent is added for mixing, and ball milling is performed by a ball mill to obtain mixed powder M; the powder M is dried at a temperature of 650-850° C. for 1.5-2 h to obtain dried powder; the powder is sieved to obtain powder N, the powder N is placed in a mold for first pressing to obtain a rough blank, and the rough blank is then pressed for the second time to obtain a compact blank; the compact blank is sintered to obtain the high-entropy rare earth-toughened tantalate ceramic.

Claims

1. A high-entropy rare earth-toughened tantalate ceramic, which is prepared by sintering Ta.sub.2O.sub.5 powder and x types of different RE.sub.2O.sub.3 powders, wherein 4≤x≤9, and the molar ratio of the RE.sub.2O.sub.3 powders is equal to 1.

2. The high-entropy rare earth-toughened tantalate ceramic according to claim 1, wherein the RE.sub.2O.sub.3 is selected from Y.sub.2O.sub.3, Pm.sub.2O.sub.3, Gd.sub.2O.sub.3, Tb.sub.2O.sub.3, Dy.sub.2O.sub.3, Ho.sub.2O.sub.3, Er.sub.2O.sub.3, Tm.sub.2O.sub.3 and Lu.sub.2O.sub.3.

3. A method for preparing the high-entropy rare earth-toughened tantalate ceramic of claim 2, comprising the following operations: operation (1): weighing the RE.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder according to a molar ratio of RE to Ta being 1:1, adding solvent for mixing, and performing ball milling to obtain mixed powder M; operation (2): drying the powder M obtained in operation (1) at a temperature of 650-850° C. for 1.5-2 h to obtain dried powder; operation (3): sieving the powder obtained in operation (2) to obtain powder N, pressing the powder N to obtain a compact blank; operation (4): sintering the compact blank obtained in operation (3) to obtain a high-entropy rare earth-toughened tantalate ceramic, the sintering temperature being 1600-1750° C., and the sintering time being 10-15 h.

4. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 3, wherein in operation (1), the ball milling speed is 400-500 r/min, and the ball milling time is 180-240 min.

5. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 3, wherein a mesh of 300-400 mesh is utilized for sieving in operation (3).

6. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 3, wherein in operation (3), the pressure of a first pressing is 6-10 MPa, and the pressing time of the first pressing is 6-10 min.

7. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 3, wherein in operation (3), the pressure of a second pressing is 350-450 MPa, and the pressing time of the second pressing is 10-30 min.

8. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 3, wherein in operation (1), the purity of the RE.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder is not less than 99.99%.

9. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 8, wherein the solvent in operation (1) is ethanol or distilled water.

10. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 9, wherein in operation (1), the molar ratio of the sum of the RE.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder to the solvent is (3:1)-(5:1).

11. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 4, wherein in operation (1), the purity of the RE.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder is not less than 99.99%.

12. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 5, wherein in operation (1), the purity of the RE.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder is not less than 99.99%.

13. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 6, wherein in operation (1), the purity of the RE.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder is not less than 99.99%.

14. The method for preparing the high-entropy rare earth-toughened tantalate ceramic according to claim 7, wherein in operation (1), the purity of the RE.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder is not less than 99.99%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 shows the X-ray diffraction pattern (XRD pattern) of the (Y.sub.1/4Gd.sub.1/4Dy.sub.1/4Er.sub.1/4)TaO.sub.4 high-entropy rare earth-toughened tantalate ceramic prepared in Embodiment 1.

[0036] FIG. 2 is a diagram showing the toughness test of (Y.sub.1/9Gd.sub.1/9Dy.sub.1/9Er.sub.1/9Lu.sub.1/9Tm.sub.1/9Ho.sub.1/9Tb.sub.1/9Pm.sub.1/9)TaO.sub.4 high-entropy rare earth-toughened tantalate ceramic prepared in Embodiment 6.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The present disclosure will be described in more detail by using the embodiments below:

[0038] A high-entropy rare earth-toughened tantalate ceramic, which is prepared by sintering Ta.sub.2O.sub.5 powder and x types of different RE.sub.2O.sub.3 powder, 4≤x≤9, and the molar ratio of the RE.sub.2O.sub.3 powders is 1; the RE.sub.2O.sub.3 powders are selected from Y.sub.2O.sub.3, Pm.sub.2O.sub.3, Gd.sub.2O.sub.3, Tb.sub.2O.sub.3, Dy.sub.2O.sub.3, Ho.sub.2O.sub.3, Er.sub.2O.sub.3, Tm.sub.2O.sub.3 or Lu.sub.2O.sub.3.

[0039] A method for preparing the high-entropy rare earth-toughened tantalate ceramic, including the following operations:

[0040] Operation (1): weighing RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder according to the molar ratio of RE to Ta being 1:1, adding distilled water or ethanol solvent for mixing, the molar ratio of the sum of RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder to the solvent being (3:1)-(5:1), and performing ball milling by a ball mill to obtain mixed powder M. The ball mill is a variable frequency planetary ball mill (model: XQM), the speed of the ball mill is 400-500 r/min, the milling time is 180-240 min, and the purity of the raw materials RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder is not less than 99.9%.

[0041] Operation (2): drying the powder M obtained in operation (1) at a temperature of 650-850° C. for 1.5-2 h to obtain dried powder.

[0042] Operation (3): sieving the powder obtained in operation (2) to obtain powder N, the sieving mesh being 300-400 mesh; placing the powder N in a mold for the first pressing to obtain a rough blank; pressing the rough blank for the second time with a cold isostatic press (model: 21955-2) to obtain a compact blank; the pressure of the first pressing is 6-10 MPa, and the pressing time is 6-10 min; the pressure of the second pressing is 350-450 MPa, and the pressing time is 10-30 min.

[0043] Operation (4): sintering the compact blank in operation (3) to obtain a high-entropy rare earth-toughened tantalate ceramic, the sintering temperature being 1600-1750° C., and the sintering time being 10-15 h; during high temperature sintering, the heating rates are as follows: heating at 5° C./min to 700° C., holding for 30 min; heating at 4° C./min to 1200° C., holding for 30 min; and heating at 1-3° C./min to 1600-1750° C.

[0044] The high-entropy rare earth-toughened tantalate ceramic with hardness of 5.61-6.56 GPa and toughness of 2.73-3.54 MPa.Math.m.sup.12 is obtained by the above method. To fully illustrate the high hardness and high toughness of the high-entropy rare earth tantalate ceramic prepared by the above method, six groups of Embodiments are selected for illustration.

[0045] Table 1 shows the specific parameters of Embodiments 1-6 of the present disclosure (a slash in the table indicates the absence of a corresponding ingredient):

TABLE-US-00001 Embodiment 1 2 3 4 5 6 RE.sub.2O.sub.3 Y.sub.2O.sub.3 0.475 0.367 0.300 0.254 0.222 0.199 (g) Pm.sub.2O.sub.3 — — — — — 0.298 Gd.sub.2O.sub.3 0.761 0.587 0.481 0.408 0.356 0.319 Tb.sub.2O.sub.3 — — — — 0.360 0.322 Dy.sub.2O.sub.3 0.785 0.605 0.495 0.421 0.367 0.328 Ho.sub.2O.sub.3 — — — 0.426 0.372 0.333 Er.sub.2O.sub.3 0.804 0.619 0.508 0.431 0.376 0.336 Tm.sub.2O.sub.3 — — 0.512 0.435 0.380 0.339 Lu.sub.2O.sub.3 — 0.646 0.528 0.448 0.392 0.350 Ta.sub.2O.sub.5(g) 5.525 5.525 5.525 5.525 5.525 5.525 Ball Speed 450 450 450 400 450 500 milling (r/min) Time (min) 200 200 180 200 200 240 Drying Temperature (° C.) 650 650 650 750 650 850 Time (h) 1.5 1.5 1.5 1.5 2 2 Sieving Sieving 300 300 300 400 400 300 mesh First Pressure of 8 8 6 8 10 8 pressing the pressing (MPa) Pressing 8 8 10 8 6 8 time (min) Second Pressure of 400 400 350 400 450 400 pressing the pressing (MPa) Pressing 15 15 30 15 10 15 time (min) Sintering Sintering 1700 1700 1700 1600 1700 1750 temperature (° C.) Sintering 10 10 10 15 10 10 time (h)

[0046] Three groups of Comparative Examples and the high-entropy rare earth-toughened tantalate ceramics obtained in Embodiments 1-6 are listed for comparative experiments:

[0047] Comparative Example 1: Comparative Example 1 differs from Embodiment 1 in that the operation (2) is not performed in Comparative Example 1.

[0048] Comparative Example 2: Comparative Example 2 differs from Embodiment 1 in that in operation (4) of Comparative Example 2, the sintering temperature is 1100-1300° C., and the sintering time is 3-5 h.

[0049] Comparative Example 3: Comparative Example 3 differs from Embodiment 1 in that only the rare earth oxide Y.sub.2O.sub.3 is added to obtain the YTaO.sub.4 ceramic in Comparative Example 3.

[0050] The ceramics of Embodiments 1-6 and Comparative Examples 1-3 are tested:

[0051] 1. Xrd Characterization:

[0052] The ceramic materials obtained in Embodiments 1-6 and Comparative Examples 1-3 are examined by X-ray diffractometer. Taking the (Y.sub.1/4Gd.sub.1/4Dy.sub.1/4Er.sub.1/4)TaO.sub.4 high-entropy ceramic obtained in Embodiment 1 as an example, the XRD pattern is shown in FIG. 1. As can be seen from the XRD test result in FIG. 1, the diffraction peaks of the (Y.sub.1/4Gd.sub.1/4Dy.sub.1/4Er.sub.1/4)TaO.sub.4 ceramic sample correspond to the standard peaks of the standard PDF card JCPDS: No. 24-1415, and there isn't any second-phase diffraction peak, indicating that the crystal structure of the prepared ceramic material is single phase and no impurity phase is produced.

[0053] Regarding Comparative Examples 1-2, some impurity phases are found by the XRD diffraction experiments. Comparative Example 1 does not have the pre-drying operation, therefore, on the one hand, there is still a certain amount of solvent or moisture in the powder M, and on the other hand, the absence of pre-deactivation treatment on the powder results in high surface activation energy of the powder M and lowered its reaction temperature, which means that tantalum oxide would react with a single species of rare earth oxide at low temperature to form a large number of second phases. Regarding Comparative Example 2, since both the sintering temperature and the sintering time have been reduced, the reaction temperature for producing a single-phase high-entropy ceramic has not been reached, thus forming impurity phases dominated by the second phase.

[0054] 2. Hardness and Toughness Testing

[0055] The hardness of the ceramics obtained in Embodiments 1-6 and Comparative Examples 1-3 is measured with a Vickers hardness tester. The fracture toughness of the material is calculated based on the diagonal length of the indentation and the crack length of the four corners. The test results are shown in Table 2 below. Taking the (Y.sub.1/9Gd.sub.1/9Dy.sub.1/9Er.sub.1/9Lu.sub.1/9Tm.sub.1/9Ho.sub.1/9Tb.sub.1/9Pm.sub.1/9)TaO.sub.4 high-entropy ceramic obtained in Embodiment 6 as an example, the toughness diagram is shown in FIG. 2.

[0056] The formula related is Vickers hardness:

[00001]$\mathrm{HV}=\frac{F}{S}=\frac{2F\sin \left(\theta /2\right)}{d^2}=1.854\frac{F}{d^2}$

(Unit: GPa), where HV represents the Vickers hardness of high-entropy ceramics, and F and d represent the test load and the diagonal length of the indentation, respectively. Fracture toughness: K.sub.IC=0.0725*(P/a.sup.3/2) (unit: Mpa.Math.m.sup.1/2), where P represents the test load, and a represents the average crack length.

[0057] Table 2 shows the results of hardness and toughness tests of Embodiments 1-6 and Comparative Examples 1-3.

TABLE-US-00002 Vickers hardness Fracture toughness (GPa) (MPa .Math. m.sup.1/2) Embodiment 1 5.61 2.73 Embodiment 2 5.83 2.76 Embodiment 3 6.07 3.01 Embodiment 4 6.29 3.22 Embodiment 5 6.42 3.45 Embodiment 6 6.56 3.54 Embodiment 1 5.57 2.54 Embodiment 2 5.3 2.34 Embodiment 3 5.15 2.37

[0058] As can be seen from the experimental results in Table 2:

[0059] (1) The more types of rare earth oxides added, the higher the hardness and toughness of the obtained rare earth-toughened ceramic materials; in this embodiment, when there are 9 types of rare earth oxides added (x=9), the hardness of the ceramic materials reaches 6.56 GPa, and the toughness of the ceramic materials reaches 3.54 Mpa.Math.m.sup.1/2.

[0060] (2) Compared with traditional rare earth tantalates, the high-entropy rare earth tantalate prepared by the present disclosure has higher hardness and toughness. Taking the (Y.sub.1/9Gd.sub.1/9Dy.sub.1/9Er.sub.1/9Lu.sub.1/9Tm.sub.1/9Ho.sub.1/9Tb.sub.1/9Pm.sub.1/9)TaO.sub.4 ceramic obtained in Embodiment 6 as an example, the hardness is 6.56 GPa and the toughness is 3.54 Mpa.Math.m.sup.1/2. As for Comparative Example 3, the hardness of YTaO.sub.4 ceramics is 5.15 GPa, and the toughness is 2.37 MPa.Math.m.sup.1/2. The results indicate that compared with the single rare earth tantalate ceramic (YTaO.sub.4 ceramic in Comparative Example 3), the hardness of the high-entropy ceramic obtained in Embodiment 6 is improved by 27.4%, and the toughness is improved by 49%.

[0061] The descriptions above are merely embodiments of the present disclosure, and common knowledge such as specific structures and features that are well-known in the schemes will not be described in detail herein. It should be noted that for those skilled in the art, variations and improvements may be made without departing from the structure of the present disclosure, these variations and improvements are within the scope of the present disclosure, and will not affect the implementation effect or practicality of the present disclosure. The protection scope of the present disclosure is subject to the protection scope defined in claims. The specific embodiments of the present disclosure may be used to interpret the content of the claims.