HIGH-ENTROPY HALF-HEUSLER THERMOELECTRIC MATERIAL WITH LOW LATTICE THERMAL CONDUCTIVITY AND PREPARATION METHOD THEREOF

Abstract

The present invention provides a high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity and a preparation method thereof. The general formula of the high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity is Zr.sub.xHf.sub.1-xNi.sub.yPd.sub.1-ySn, where x is equal to 0.6 to 0.8, and y is equal to 0.8 to 0.9. The preparation method of the high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity comprises the following steps: preparing and mixing materials according to the general formula of Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn, putting the mixed raw materials in a levitation melting for melting, grinding the obtained ingot into powder and drying it, and sintering the powder by using spark plasma sintering into a bulk high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity. The high-entropy Half-Heusler thermoelectric material of the present invention has a relatively low lattice thermal conductivity and a relatively high ZT value.

Claims

1. A high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity, wherein the general formula is Zr.sub.xHf.sub.1-xNi.sub.yPd.sub.1-ySn, wherein x is equal to 0.6 to 0.8, and y is equal to 0.8 to 0.9.

2. A preparation method of a high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity, comprising the following steps: preparing and mixing materials according to the general formula of Zr.sub.xHf.sub.1-xNi.sub.yPd.sub.1-ySn, in which x is equal to 0.6 to 0.8 and y is equal to 0.8 to 0.9, putting a mixture in a levitation melting furnace for melting, grinding the obtained ingot into powder and drying the powder, and sintering the powder by spark plasma sintering into a bulk high-entropy Half-Heusler thermoelectric alloy sample with a low lattice thermal conductivity.

3. The preparation method of a high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity according to claim 2, comprising the following steps: (1) preparing and mixing materials according to the general formula of Zr.sub.xHf.sub.1-xNi.sub.yPd.sub.1-ySn in a glovebox; (2) putting the mixed raw materials in a levitation melting furnace for melting under an argon atmosphere: raising the temperature to 1600-1800 C., and then holding the temperature for 1-5 min; (3) ball-milling the obtained ingot into powder with the diameter of 0.5-2 m; (4) drying the obtained powder; and (5) sintering the powder by spark plasma sintering, wherein the sintering temperature is 800-1000 C., the sintering pressure is 80-100 MPa, and the holding time is 5-20 min.

4. The preparation method of a high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity according to claim 3, wherein the pressure of the argon atmosphere in the step (2) is 10.sup.4-10.sup.5 Pa.

5. The preparation method of a high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity according to claim 3, wherein the melting in the step (2) is repeatedly performed 3-6 times.

6. The preparation method of a high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity according to claim 3, wherein the ball-milling in the step (3) comprises the following steps: firstly roughly grinding the ingot into powder with the diameter of 0.1-1 mm by using a mortar and pestle, and then wet ball-grinding under an argon atmosphere, wherein the ball-milling medium is absolute ethyl alcohol, and the mass ratio between balls and powder is 10:1 to 20:1, the rotating speed is 200-600 r/min, and the ball-milling time is 5-20 h.

7. The preparation method of a high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity according to claim 3, wherein the drying in step (4) comprises the step of naturally drying the powder for 12-48 h after suction filtration in the glovebox.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 shows XRD patterns of bulk samples with different compositions after spark plasma sintering.

[0022] FIG. 2 shows the total thermal conductivity of the pristine ZrNiSn and the Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn high-entropy Half-Heusler thermoelectric alloy.

[0023] FIG. 3 shows the lattice thermal conductivity of the pristine ZrNiSn and the Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn high-entropy Half-Heusler thermoelectric alloy.

DETAILED DESCRIPTION OF THE DRAWINGS

[0024] The description of the present invention is further described in conjunction with the following embodiments.

Embodiment 1

[0025] The embodiment discloses a high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity, and it is melted according to the nominal composition of Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn, where the atomic percent of each element is as follows: Zr, 23.3%; Hf, 10%; Ni, 28.3%; Pd, 5%; and Sn, 33.3%.

[0026] The further improvement of the present invention lies in that:

[0027] The grain size of the obtained Half-Heusler thermoelectric material is 0.5-2 m.

[0028] The preparation method of the high-entropy Half-Heusler thermoelectric material with a low lattice thermal conductivity includes the following steps:

[0029] (1) preparing materials according to the nominal composition of Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn in a glovebox;

[0030] (2) melting: mixed raw materials are melted in a levitation melting furnace under an argon atmosphere (10.sup.4-10.sup.5 Pa), after raising the temperature to 1600-1800 C., then holding the temperature for 3 min. The obtained ingot is repeatedly melted four times in order to keep the homogeneous microstructure;

[0031] (3) ball-milling: the ingot is firstly roughly grinded into powder with the diameter of 0.1-1 mm by using a mortar and pestle; and then wet ball-milling is carried out under an argon atmosphere, where the ball-milling medium is absolute ethyl alcohol, and the mass ratio between balls and powder is 15:1, the rotating speed is 500 r/min, and the ball-milling time is 10 h;

[0032] (4) drying: the powder is naturally dried for 24 h after suction filtration in a glovebox; and

[0033] (5) sintering: the prepared powder is sintered into a bulk sample by spark plasma sintering, where the sintering temperature is 900 C., the sintering pressure is 100 MPa, and the holding time is 15 min.

[0034] Experimental Result

[0035] FIG. 1 shows the XRD patterns of bulk samples with different compositions after spark plasma sintering. All the XRD patterns of the pristine ZrNiSn and Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn high-entropy Half-Heusler thermoelectric samples with x0.06 are indexed as a single phase;

[0036] FIG. 2 shows the total thermal conductivity of the pristine ZrNiSn and Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn high-entropy Half-Heusler thermoelectric alloy. A low total thermal conductivity of 4.09 mW/mK.sup.2 is achieved at 923K, which is reduced by 17% compared with that of the pristine ZrNiSn.

[0037] FIG. 3 shows the lattice thermal conductivity of the pristine ZrNiSn and Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn high-entropy Half-Heusler thermoelectric alloy. The lattice thermal conductivity of the high-entropy Half-Heusler alloy is reduced to 2.76 mW/mK.sup.2 at 923 K, which is compared with that of the pristine ZrNiSn.

[0038] In the embodiment, a high-entropy alloy design idea is introduced into the preparation of the Half-Heusler thermoelectric alloy, so that the lattice thermal conductivity of the Half-Heusler thermoelectric alloy is remarkably reduced by an obvious lattice distortion field generated by a high-entropy effect, and it will provide more opportunities for the industrial applications of moderate and high-temperature Half-Heusler thermoelectric materials. Through the present invention, a single-phase Zr.sub.0.7Hf.sub.0.3Ni.sub.0.85Pd.sub.0.15Sn high-entropy Half-Heusler thermoelectric alloy is successfully prepared, and a low total thermal conductivity of 4.09 mW/mK.sup.2 and a low lattice thermal conductivity of 2.76 mW/mK.sup.2 are achieved at 923K.

Embodiment 2

[0039] The further improvement of the present invention lies in that: The preparation method of a high-entropy Heusler alloy with a low lattice thermal conductivity includes the following steps:

[0040] (1) preparing materials according to the nominal composition of Zr.sub.0.6Hf.sub.0.4Ni.sub.0.8Pd.sub.0.2Sn in a glovebox;

[0041] (2) melting: mixed raw materials are melted in a levitation melting furnace under an argon atmosphere (10.sup.4-10.sup.5 Pa), after raising the temperature to 1600-1800 C., then holding the temperature for 4 min, The obtained ingot is repeatedly melted four times in order to keep the homogeneous microstructure; (3) ball-milling: the ingot is firstly roughly grinded into powder with the diameter of 0.1-1 mm by using a mortar and pestle; and then wet ball-milling is carried out under an argon atmosphere, where the ball-milling medium is absolute ethyl alcohol, and the mass ratio between balls and powder is 20:1, the rotating speed is 600 r/min, and the ball-milling time is 8 h;

[0042] (4) drying: the powder is naturally dried for 20 h after suction filtration in a glovebox; and

[0043] (5) sintering: the prepared powder is sintered into a bulk sample by spark plasma sintering, where the sintering temperature is 850 C., the sintering pressure is 90 MPa, and the holding time is 20 min.

[0044] Finally, it should be noted that the foregoing embodiments are merely intended for describing the technical solutions of the present invention, but not for limiting the present invention. Although the present invention is described in detail with reference to the foregoing embodiments, persons of ordinary skill in the art should understand that they may still make modifications to the technical solutions described in the foregoing embodiments or make equivalent replacements to some or all technical features thereof, without departing from the scope of the technical solutions of the embodiments of the present invention.