Tuning the Intermediate Valence Behavior in the Zintl Compound Yb14ZnSb11 by Incorporation of RE3+ [Yb14-xRExZnSb11 (0.2 ≤ x ≤ 0.7), RE = Sc, Y, La, Lu and Gd].

The solid solutions of Yb14-xRExZnSb11 (RE = Sc, Y, La, Lu, and Gd; 0.2 ≤ x ≤ 0.7) were prepared to probe the intermediate valency of Yb in Yb14ZnSb11. The substitution of Yb with RE3+ elements should reduce or remove the intermediate valency of the remaining Yb ions. Large crystals are grown from Sn-flux, and the structure and magnetic susceptibility are presented. All compounds crystallize in the Ca14AlSb11 structure type and the RE3+ ions show Yb site substitution preferences that correlate with size. Two compositions of Yb14-xYxZnSb11 were investigated [x = 0.38(3), 0.45(3)] by temperature-dependent magnetic susceptibility and the broad feature in magnetic susceptibility measurements at 85 K in pristine Yb14ZnSb11 attributed to valence fluctuation decreases and is absent for x = 0.45(3). In compounds with nonmagnetic RE3+ substitutions (Sc, Y, La, and Lu), temperature-dependent magnetic susceptibility shows a transition from intermediate valency fluctuation toward temperature-independent (Y, La, and Lu) or Curie-Weiss behavior and possibly low temperature heavy Fermion behavior (Sc). In the example of the magnetic rare earth substitution, RE = Gd, the Curie-Weiss-dependent magnetic moment of Gd3+ is consistent with x. Hall resistivity of Yb14-xYxZnSb11 showed that the carrier concentration decreases with x and the signature of the low-T intermediate valence state seen for x = 0 is suppressed for x = 0.38 and gone for x = 0.45.

Crystal structure characterization and electronic structure of a rare-earth-containing Zintl phase in the Yb-Al-Sb family: Yb3AlSb3.

A rare-earth-containing compound, ytterbium aluminium antimonide, Yb3AlSb3 (Ca3AlAs3-type structure), has been successfully synthesized within the Yb-Al-Sb system through flux methods. According to the Zintl formalism, this structure is nominally made up of (Yb2+)3[(Al1-)(1b - Sb2-)2(2b - Sb1-)], where 1b and 2b indicate 1-bonded and 2-bonded, respectively, and Al is treated as part of the covalent anionic network. The crystal structure features infinite corner-sharing AlSb4 tetrahedra, [AlSb2Sb2/2]6-, with Yb2+ cations residing between the tetrahedra to provide charge balance. Herein, the synthetic conditions, the crystal structure determined from single-crystal X-ray diffraction data, and electronic structure calculations are reported.