Thermoelectric Performance Enhancement of the Cost-Effective Phosphide ZnCu₂P₈

Abstract

A facile bulk ball milling synthesis for the abundant and inexpensive compound ZnCu 2 P 8 was developed. Stoichiometries of Zn 1−x Cu 2+x P 8 (x = −0.25, 0, 0.1, 0.25) were synthesized and characterized through X-ray diffraction, EDS, diffuse reflectance, and high-temperature transport properties. The series exhibits low thermal conductivities near 1.0 W m −1 K −1 at 673 K and an enhancement of zT up to 0.25, a 150% increase compared to the parent phase. The measured thermoelectric properties are within the range of the best performing phosphides; however, a more in-depth study on the control of the phosphorus stoichiometry is required to realize full thermoelectric potential.

Exceptional Thermoelectric Performance Enabled by High Carrier Mobility and Intrinsically Low Lattice Thermal Conductivity in Phosphide Cd3P2

“…Combined with the significant enhancement of electrical conductivity, the PFs are consequently enhanced in the whole temperature range with increasing carrier density as presented in Figure e. The maximum of the PFs occur at 673 K for all samples, and the highest value of 1.3 mW m –1 K –2 is achieved in sample HP923-P 1.94 with a maximum carrier density, which is superior to the existing TE phosphides. ,− …”

“…The temperature dependence of the total thermal conductivity ( κ tot ) is presented in Figure a. κ tot is lower than 1.1 W m –1 K –1 in the whole temperature range indicating a relatively low value among phosphides. ,− For all samples, κ tot first decreases with the elevating temperature and subsequently increases due to the bipolar effect. Consequently, by subtracting the electronic component κ e from κ tot , the sum of lattice and bipolar thermal conductivities ( κ L + κ bi < 1.0 W m –1 K –1 ) is depicted in Figure b.…”

“…However, phosphides have been ignored in most TE explorations because of potentially high lattice thermal conductivity stemmed from their light mass and strong covalent bonds. 16 Nevertheless, materials with intrinsically low thermal conductivity still exist in some complex phosphides, such as Ba 8 Au 16 P 30 and Ba 2 Si 3 P 6 , in which the lattice thermal conductivities are as low as 0.20 and 0.56 W m −1 K −1 at 300 K, respectively, 17,18 implying the potentialities of TE study for phosphides. Complex lattice in phosphides, generally, impede the high mobility of the carrier, leading to the absence of strong attractiveness.…”

“…At present, the investigation on TE materials mainly focuses on IV–VI, − I–III–VI, − and VIII–V , compounds, in which most compounds exhibit excellent TE performance with peak zT over 1.0. However, phosphides have been ignored in most TE explorations because of potentially high lattice thermal conductivity stemmed from their light mass and strong covalent bonds . Nevertheless, materials with intrinsically low thermal conductivity still exist in some complex phosphides, such as Ba 8 Au 16 P 30 and Ba 2 Si 3 P 6 , in which the lattice thermal conductivities are as low as 0.20 and 0.56 W m –1 K –1 at 300 K, respectively, , implying the potentialities of TE study for phosphides.…”

New sustainable ternary copper phosphide thermoelectrics

“…Metal phosphides are currently attracting wider interest as potential thermoelectric materials, 3 inspired by the success of Zintl phases based on Sb, 4 and the realisation that despite the low atomic mass of P, complex crystal structures can still have low lat, while small electronegativity differences support good electrical properties. Recently investigated phosphides include cage-like tetrahedrite Ag6Ge10P12 with zT = 0.7 at 750 K, 5,6 layered CaZn2P2 and YbCuZnP2 materials with zT = 0.6 at 973 K for YbCuZnP2, [7][8][9] the clathrate Ba8Cu14Ge6P26 with zT = 0.6, 10 Zn1-xCu2P8 with zT = 0.25 at 673 K, 11 and tetragonal Cd3P2 with zT = 0.9 at 673 K. 12,13 We have recently reported a related ternary silver phosphide, CaAg1-xP (x = 0.1), containing cornerand edge-sharing AgP5 square pyramids, achieving a highest zT = 0.4 at 800 K. 14 MgCuP and CaCuP were first synthesised in the 1970s but have not been investigated for their properties. 15,16 The crystal structures of MgCuP and CaCuP are illustrated in Fig.…”