Anomalous Thermal Conductivity of Cd3As2 and the Cd3As2−Zn3As2 Alloys

Abstract

The room-temperature lattice thermal conductivity of Zn3As2 is 0.012 W/cm·°C; that of Cd3As2 is 0.014 W/cm·°C or less. Anomalously low thermal conductivities (as much as 30% below calculated values) are found for samples of Cd3As2 and Cd-rich alloys of Cd3As2 with Zn3As2 where the electrical conductivity is high (>103 Ω−1 cm−1). Thermal conductivities for Cd3As2 samples fall into two groups: Samples doped with an element which is expected to enter the anion sublattice have normal thermal conductivities, while undoped samples or those doped with an element which should enter the cation sublattice tend to have anomalously low thermal conductivities. High electron mobilities and general lack of correlation of carrier concentration with thermal conductivity indicate that the anomaly is not in the electronic component of thermal conductivity. Instead, doping experiments, as well as the temperature dependencies of thermal conductivities indicate that the anomaly is entirely in the lattice component and is due to a lattice defect in the anion sublattice, probably an As vacancy. Although the lattice thermal conductivity of some samples of Cd3As2 appears to be only 0.003–0.004 W/cm·°C, their electron mobility is 104 cm2/V·sec. To explain the apparently enormous phonon scattering cross-section of the lattice defect, it is suggested that the phonon scattering may involve the transitions of localized electrons from one type of As site (vacancy) to another (there are three different types of As sites in Cd3As2).

Negative magnetoresistance due to conductivity fluctuations in films of the topological semimetal Cd3As2

“…The phase diagram for Cd 3 As 2 shows a line compound that opens up to a phase field towards the Cd-rich side, i.e., Cd 3 As 2−δ , at higher temperatures [24]. This leads to higher concentrations of As vacancies, which are the source of unintentional n-type doping in Cd 3 As 2 [25]. The Hall mobility (Table I) increased with film thickness either due to a reduction in scattering from the interface with the buffer layer or annihilation of extended defects with increasing thickness.…”

Structural properties and growth mechanism of Cd3As2 nanowires

“…As vacancies) lead to an unusually high phonon scattering rate decreasing the thermal conductivity and increasing the thermoelectric figure of merit. 6,7 A high electron mobility and large figure of merit are beneficial for applications of Cd 3 As 2 in thermoelectric devices.…”

IBRAGIM IBISHEVICH IBRAGIMOV (on his sixtieth birthday)

“…The exact shape of the curve is not certain as the lack of a suitable temperature bath did not allow many values of thermal conductivity around the minimum to be obtained. The increase in thermal conductivity as the temperature is reduced below 1 0 0 "~ can be attributed to a decrease in the lattice component of the thermal conductivity, which is inversely proportional to temperature, Spitzer et al (1966) obtained a lattice component which was independent of temperature above 2 3 0 "~, and it is likely that conduction has ceased to be by lattice waves at such temperatures (Drabble and Goldsmid 1961, p. 184).…”