Motivated by excellent thermoelectric performance in the well-known Yb-based Zintl compounds Yb₁₄MnSb₁₁ and YbZn_2−xMn_xSb₂, this study investigates the thermoelectric properties of Yb₉Mn_4.2Sb₉. Unlike most transition metal containing Zintl phases, Yb₉Mn_4.2Sb₉ contains a partially occupied Mn site and thus does not have a valence-precise stoichiometry. Samples were synthesized by direct ball milling of the elements, followed by hot pressing. Consistent with previous reports, X-ray diffraction and wavelength dispersive spectroscopy confirmed a narrow composition range near Yb₉Mn_4.2Sb₉. High temperature measurements of the electronic properties of Yb₉Mn_4.2Sb₉ indicate that it is a degenerate p-type semiconductor with a band gap sufficiently large for high temperature thermoelectric applications. Hall measurements reveal that Yb₉Mn_4.2Sb₉ has a high extrinsic carrier concentration (∼10²⁰ h⁺ cm⁻³), which is due to the deviation from the theoretical “Zintl composition” of Yb₉Mn_4.5Sb₉. The measured carrier concentration coincides with the optimum concentration predicted using a single parabolic band model. Measurements of the thermal diffusivity and heat capacity reveal an extremely low, temperature-independent lattice thermal conductivity in this compound (κ_L < 0.4 W mK⁻¹), which is due to both the large unit cell size (44 atoms per primitive cell) and substantial disorder on the Mn site. This favorable combination of optimized electronic properties and low lattice thermal conductivity leads to a promising figure of merit at high temperature (zT = 0.7 at 950 K).

Intermetallic compounds with the equiatomic composition CeTX that crystallize with the orthorhombic TiNiSi-type structure can be synthesized with electron-rich transition metals (T) and X = Zn, Al, Ga, Si, Ge, Sn, As, Sb, and Bi. The present review focusses on the crystal chemistry and chemical bonding of these CeTX phases and on their physical properties, ¹¹⁹Sn and ¹²¹Sb Mössbauer spectra, high-pressure effects, hydrogenation reactions and the formation of solid solutions in order to elucidate structure–property relationships. This paper is the final one of a series of four reviews on equiatomic intermetallic cerium compounds [Part I: Z. Naturforsch. 2015, 70b, 289; Part II: Z. Naturforsch. 2015, 70b, 695; Part III: Z. Naturforsch. 2016, 71b, 165].

The physical properties of the first In analog of the PuMGa(5) (M = Co, Rh) family of superconductors, PuCoIn(5), are reported. With its unit cell volume being 28% larger than that of PuCoGa(5), the characteristic spin-fluctuation energy scale of PuCoIn(5) is three to four times smaller than that of PuCoGa(5), which suggests that the Pu 5f electrons are in a more localized state relative to PuCoGa(5). This raises the possibility that the high superconducting transition temperature T(c) = 18.5 K of PuCoGa(5) stems from the proximity to a valence instability, while the superconductivity at T(c) = 2.5 K of PuCoIn(5) is mediated by antiferromagnetic spin fluctuations associated with a quantum critical point.

The structure–property relationships of CeTXintermetallics with structures other than the ZrNiAl and TiNiSi type are systematically reviewed. These CeTXphases form with electron-poor and electron-rich transition metals (T) andX= Mg, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, and Bi. The review focusses on the crystal chemistry, the chemical bonding peculiarities, and the magnetic and transport properties. Furthermore¹¹⁹Sn Mössbauer spectroscopic data, high-pressure studies, hydrogenation reactions and the formation of solid solutions are reviewed. This paper is the third of a series of four reviews on equiatomic intermetallic cerium compounds [Part I: R. Pöttgen, B. Chevalier,Z. Naturforsch.2015,70b, 289; Part II: R. Pöttgen, B. Chevalier,Z. Naturforsch.2015,70b, 695].

The reason for the capacity fading of LiFePO₄ in lithium recovery is explored. And two approaches, reducing the content of oxygen and carbon coating, are put forward, and the mechanism of them are studied.