Reduction of Thermal Conductivity for Icosahedral Al-Cu-Fe Quasicrystal through Heavy Element Substitution

Icosahedral Al-Cu-Fe quasicrystal (QC) shows moderate electrical conductivity and low thermal conductivity, and both p- and n-type conduction can be controlled by tuning the sample composition, making it potentially suited for thermoelectric materials. In this work, we investigated the effect of introducing chemical disorder through heavy element substitution on the thermal conductivity of Al-Cu-Fe QC. We substituted Au and Pt elements for Cu up to 3 at% in a composition of Al63Cu25Fe12, i.e., Al63Cu25−x(Au,Pt)xFe12 (x = 0, 1, 2, 3). The substitutions of Au and Pt for Cu reduced the phonon thermal conductivity at 300 K (κph,300K) by up to 17%. The reduction of κph,300K is attributed to a decrease in the specific heat and phonon relaxation time through heavy element substitution. We found that increasing the Pt content reduced the specific heat at high temperatures, which may be caused by the locked state of phasons. The observed glass-like low values of κph,300K (0.9–1.1 W m−1 K−1 at 300 K) for Al63Cu25−x(Au,Pt)xFe12 are close to the lower limit calculated using the Cahill model.

Влияние мультиплетных уровней Sm-=SUP=-3+-=/SUP=- и Eu-=SUP=-3+-=/SUP=- на теплоемкость мультиферроика BiFeO-=SUB=-3-=/SUB=-

The temperature dependence of the heat capacity of the multiferroics BiFeO3, Bi0.90Sm0.10FeO3, and Bi0.90Eu0.10FeO3 has been studied. It was found that the substitution of europium and samarium ions for bismuth ions in bismuth ferrite leads to the appearance of an additional heat capacity component due to transitions of 4f - electrons of rare earth ions to higher levels of the multiplet. A connection is established between the decrease in phonon thermal conductivity and the Schottky effect for the specific heat.

Phonon thermal conductivity of the stanene/hBN van der Waals heterostructure

We found that the phonon thermal conductivity (PTC) of bare hBN and stanene could be engineered by assembling them in the form of a vertical heterostructure.