Structural Features, Anisotropic Thermal Expansion, and Thermoelectric Performance in Bulk Black Phosphorus Synthesized under High Pressure

Abstract

Black phosphorus (BP) allotrope has an orthorhombic crystal structure with a narrow bandgap of 0.35 eV. This material is promising for 2D technology since it can be exfoliated down to one single layer: the well-known phosphorene. In this work, bulk BP was synthesized under high-pressure conditions at high temperatures. A detailed structural investigation using neutron and synchrotron X-ray diffraction revealed the occurrence of anisotropic strain effects on the BP lattice; the combination of both sets of diffraction data allowed visualization of the lone electron pair 3s 2 . Temperature-dependent neutron diffraction data collected at low temperature showed that the a axis (zigzag) exhibits a quasi-temperature-independent thermal expansion in the temperature interval from 20 up to 150 K. These results may be a key to address the anomalous behavior in electrical resistivity near 150 K. Thermoelectric properties were also provided; low thermal conductivity from 14 down to 6 Wm −1 K −1 in the range 323−673 K was recorded in our polycrystalline BP, which is below the reported values for singlecrystals in literature.

SnSe:Kx intermetallic thermoelectric polycrystals prepared by arc-melting

“…Tin selenide, SnSe, is a semiconductor with a quasi-2D laminar crystal structure resembling that of black phosphorous, also a potential thermoelectric [54]. In 2014, single crystals of SnSe were found to be the best thermoelectric up then with zT * 2.6 [55].…”

Anisotropic Behavior of Thermoelectric Power in Zigzag and Armchair 2D Phosphorene

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] According to these works, few-layer BP can reach Seebeck coefficient up to 2000 μV K À1 depending on doping level. [13] Measurements of TEP in bulk BP by Flores et al are reported to be 330 μV K À1 at T ¼ 300 K. [13] The Seebeck coefficient at the higher temperature range reported by Zeng et al shows the decreasing trend beyond a peak [14] and similar results are shown by Rodrigues et al [18] These results are comparable with the theoretical predictions. [12,19] Wang et al measured orientation-dependent Seebeck coefficient and reported the anisotropy in bulk BP.…”

Electrical and galvanomagnetic properties of black phosphorus single crystals

“…1990 [2,6,[20][21][22][23][24] and after 2014 [1, 3-5, 7-19, 25-33] when interest to b-P arose again due to the production of b-P single crystals having a higher structural perfection. There are multiple literary data on the electrical resistivity and Hall effect of bulk b-P single crystals over a wide range of temperatures and magnetic fields [20][21][22][23][24][25][26][27][28] and at different pressures. These data show that the room temperature electrical resistivity ρ 300 and the Hall mobility µ 300 of bulk b-P specimens exhibit a large scatter, i.e., 0.02-60 Ohm and 30-4000 cm 2 /(V • s), respectively.…”

“…This wide scatter of these parameters is primarily caused by the difference in the structural perfection of tested crystals. Studies of ρ(Т) for bulk b-P specimens over a wide temperature range (2-725 K) [20][21][22][23][24][25][26][27][28]33] showed a quite complex pattern of the temperature dependences of their electrical resistivity ρ(Т). It was also shown [20][21][22][23][24][25][26][27][28]33] that with an increase in temperature ρ(Т) of b-P crystals initially decreases reaching a minimum at approx.…”

“…Studies of ρ(Т) for bulk b-P specimens over a wide temperature range (2-725 K) [20][21][22][23][24][25][26][27][28]33] showed a quite complex pattern of the temperature dependences of their electrical resistivity ρ(Т). It was also shown [20][21][22][23][24][25][26][27][28]33] that with an increase in temperature ρ(Т) of b-P crystals initially decreases reaching a minimum at approx. 60-100 K, reaches a maximum at 250-500 K and then starts to decline again.…”