Method for obtaining two-dimensional metal oxide material with high thermoelectric performance

Abstract

The invention discloses a method for obtaining a two-dimensional metal oxide material with high thermoelectric performance. A method for replacing transition metal atoms in a single-layer transition metal oxide with silver clusters is adopted to obtain a single-layer silver oxide two-dimensional material corresponding to the silver clusters. The method is suitable for replacing various transition metal oxides XO2 (X = Ti, Zr, Hf and Ir). The first principle calculation shows that the single-layer silver oxide material obtained through silver cluster substitution has good stability and good practicability. The material with an electron energy gap of 1.44 electron volts is suitable for being used as a thermoelectric material. Research on electron and phonon transport characteristics shows that the single-layer silver oxide has high conductivity and extremely low phonon thermal conductivity (at room temperature, the phonon thermal conductivity is only 0.16 watt / meter Kelvin), and the single-layer silver oxide is an ideal thermoelectric material.

Description

Technical Field

[0001] New material design and application invention. Background Art

[0002] With the rapid development of the field of two-dimensional materials, transition metal oxides (TMOs) XO2 (X = Ti, Zr, Hf, Ir) two-dimensional materials have gradually become a research hotspot due to their excellent stability, unique physical and chemical properties, and great application potential in field effect transistors (FETs) and optoelectronics. 2 It is reported to be an ideal dielectric layer for FET and heterojunction. 2 With low hole effective mass, they can be used as gate oxides in high-performance electronic devices. However, their insulating properties limit their application in thermoelectrics. Single-layer TMOs usually have a large energy gap (e.g. single-layer TiO 2 , ZrO2 and HfO 2 The reported energy gaps are 3.29 eV, 7.51 eV, and 6.73 eV, respectively) and strong phonon heat transport, which suppress the TE conversion efficiency of monolayer TMOs. Therefore, it is necessary to further design monolayer TMOs with semiconductor properties.

[0003] Recent studies have shown that the properties of metal clusters with a certain number of valence electrons in crystals are very similar to those of the corresponding simple atoms. For example, a single layer of Ag with [Ag6]4+ clusters 6 Cl 4 and monolayer Ag 6 S 2 With good stability, Mariana Derzsi et al. observed that monolayer Ag 6 Cl 4 All the characteristics of Ag+ in [Ag6]4+. Importantly, Ag clusters have been successfully synthesized and have received widespread attention. Zhang et al. successfully obtained stable Ag6 clusters using Ti16-oxygen clusters with cavities, and proved that Ag6 clusters easily form coordination bonds with O atoms. From the perspective of TE applications, Ag-Ag metal bonds can provide more free electrons leading to high conductivity, and the complex structure of [Ag6]4+ clusters can cause more tortuous phonon scattering paths. Therefore, 2D transition metal oxides designed using [Ag6]4+ clusters as primitives are likely to have strong electron transport and weak phonon transport properties, thereby having high thermoelectric performance. Summary of the invention

[0004] The present invention proposes to replace the transition metal atoms in the monolayer TMOs with [Ag6]4+ clusters to obtain silver oxide with high thermoelectric performance of the corresponding structure. 6 O2 We first analyzed and designed a single-layer Ag 6 O 2 The crystal structure of the single layer Ag was calculated using the obtained crystal structure. 6 O 2 The formation energy of the designed single-layer Ag 6 O 2 Electronic structure and stability calculations show that: Ag monolayer 6 O 2 It has good stability and a narrow band gap of 1.14 eV, making it suitable as a thermoelectric material. Calculations of the electron and phonon transport properties show that: 6 O 2 It has high electrical conductivity and extremely low phonon thermal conductivity (at 300 K, the phonon thermal conductivity is only 0.16 W·m -1 ·K -1 ), at 300 K, 500 K and 700 K, the single layer Ag in n-type doped environment 6 O 2 The ZT values ​​of these materials are 1.44, 2.64 and 3.77 respectively, which makes them an ideal thermoelectric material. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 .Single layer Ag 6 O 2 Schematic diagram of the crystal structure: (a) top view; (b) side view.

[0006] Figure 2 .Single layer Ag 6 O 2 The electronic and phonon dispersion relations of the ionosphere. (a) Band structure (left) and electronic density of states (right); (b) Phonon spectrum (left) and phonon density of states (right).

[0007] Figure 3 .Single layer Ag 6 O 2 Crystal equilibrium structure diagram at 700 K and the curve of free energy change with time within 4 ps.

[0008] Figure 4 . Single layer Ag 6 O 2 The conductivity of the n-type doped type is shown in Figure 2. (a) The conductivity of the n-type doped type varies with the electron concentration; (b) The conductivity of the p-type doped type varies with the hole concentration.

[0009] Figure 5 . Single layer Ag at 3 different temperatures: 300 K, 500 K, and 700 K 6O 2 The Seebeck coefficient S of the n-type doping type. (a) The curve of the Seebeck coefficient of the n-type doping type changing with the electron concentration; (b) The curve of the Seebeck coefficient of the p-type doping type changing with the hole concentration.

[0010] Figure 6 . N-type and P-type single-layer Ag 6 O 2 Power factor changes with doping concentration.

[0011] Figure 7 . Single layer Ag 6 O 2 Phonon transport parameters. (a) Comparison of phonon thermal conductivity obtained by RTA and Iterative methods at different temperatures; (b) Phonon lifetime at different frequencies; (c) Phonon group velocity at different frequencies; (d) Contribution of phonons at different frequencies to thermal conductivity.

[0012] Figure 8 . Single layer Ag at 3 different temperatures: 300 K, 500 K, and 700 K 6 O 2 Thermoelectric figure of merit of the method proposed in the present invention. (a) Thermoelectric figure of merit of n-type doping type varies with electron concentration; (b) Thermoelectric figure of merit of p-type doping type varies with hole concentration.

[0013] Silver oxide Ag obtained by cluster replacement in the present invention 6 O 2 The formation energy is -2.35 eV and it is easy to synthesize.

[0014] Transition metal oxides usually have a large energy gap and are not suitable as thermoelectric materials. The single-layer metal oxide Ag obtained by cluster replacement in the present invention 6 O 2 The electron energy gap is 1.14 eV, which is very suitable as a thermoelectric material (such as Figure 2 as shown).

[0015] The silver oxide Ag obtained by the present invention 6 O 2 Each [Ag6]4+ cluster of the two-dimensional material is connected to 6 O atoms, and each O is connected to 3 Ag atoms. The free energy change shows that it has excellent stability at 300-700K (see Figure 1 and Figure 3 ).

[0016] Excellent thermoelectric materials require low thermal conductivity. The silver oxide Ag obtained by the present invention 6 O 2Two-dimensional materials have extremely low phonon thermal conductivity, which is only 0.16 W·m at 300 K. -1 ·K -1 , suitable as thermoelectric materials (such as Figure 7 as shown).

[0017] Single-layer Ag in n-type doped environment at 300 K, 500 K, and 700 K 6 O 2 The ZT values ​​are 1.44, 2.64 and 3.77 respectively (e.g. Figure 8 as shown).

Claims

1. The single-layer silver oxide two-dimensional material obtained by silver cluster substitution has good synthesizability. First-principles calculations show that the single-layer Ag 6 O 2 The formation energy is -2.35 eV. Each [Ag6]4+ cluster is connected to 6 O atoms, each O is connected to 3 Ag atoms, with the Ag-Ag bond length being 2.78 Å and the Ag-O bond length being 2.09 Å (Figure 1).

2. Single layer Ag 6 O 2 The electronic energy gap is 1.14 eV (Figure 2). The valence band maximum (VBM) and conduction band minimum (CBM) are located at the high symmetry points M and Γ in the Brillouin zone, respectively.

3. Single layer Ag 6 O 2 The cohesive energy is -1.65 eV / atom, and the free energy change is very small (see Figure 3), indicating that the material has good stability.

4. At a temperature of 300 K and a carrier concentration of 1×10 11 cm -2 Under the condition of n-type doped single layer Ag 6 O 2 The electrical conductivity is about 1115 S·m -1 (Figure 4).

5. At 300 K, P-type doped single layer Ag 6 O 2 The maximum Seebeck coefficient reaches 726.92 μV·K -1 (Figure 5).

6. At 300 K, n-type single-layer Ag 6 O 2 The maximum power factor PF is 1.37 mW·m −1 ·K −2 (Figure 6).

7. Single-layer Ag in n-type doped environment at 300 K, 500 K, and 700 K 6 O 2 The ZT values ​​of the samples were 1.44, 2.64 and 3.77, respectively (Fig. 7).

Images