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Title: Achieving zT > 1 in Inexpensive Zintl Phase Ca 9 Zn 4+ x Sb 9 by Phase Boundary Mapping
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Functional Materials
Page Range / eLocation ID:
Medium: X
Sponsoring Org:
National Science Foundation
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  1. null (Ed.)
  2. Abstract

    C(1)‐vinylation of [closo‐1‐CB9H10](A) and [closo‐1‐CB11H12](B) with 4‐benzyloxystyryl iodide followed by hydrogenation of the double bond and reductive deprotection of the phenol functionality led to C(1)‐(4‐hydroxyphenethyl) derivatives. The phenol functionality was protected as the acetate. The esters were then treated with PhI(OAc)2and the resulting isomers were separated kinetically (for derivatives of anionA) or by chromatography (for derivatives of anionB) giving the difunctionalized building blocks in overall yields of 9 % and 50 %, respectively. A similar series of reactions was performed starting with anionsAandBand 4‐methoxystyryl bromide and iodide. Significant differences in the reactivity of derivatives of the two carborane anions were rationalized with DFT computational results. Application of the difunctionalized carboranes as building blocks was demonstrated through preparation of two ionic liquid crystals. The extensive synthetic work is accompanied by single crystal XRD analysis of six derivatives.

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  3. We constructed the magnetic field-temperature phase diagrams of new quasi-two-dimensional isosceles triangular lattice antiferromagnets (TLAF) Ca 3 MNb 2 O 9 (M=Co, Ni) from dc and ac magnetic susceptibilities, specific heat, dielectric constant, and electric polarization measurements on single crystalline samples. Ca 3 CoNb 2 O 9 with effective spin-1/2 Co 2+ ions undergoes a two-step antiferromagnetic phase transition at T N1 = 1.3 K and T N2 = 1.5 K and enters a stripe ordered state at zero magnetic field. With increasing field, successive magnetic phase transitions, reminiscent of the up-up-down ( uud ) and the oblique phases, are observed. The dielectric constant of Ca 3 CoNb 2 O 9 shows anomalies related to the magnetic phase transitions, but clear evidence of ferroelectricity is absent. Meanwhile, Ca 3 NiNb 2 O 9 with spin-1 Ni 2+ ions also shows a two-step antiferromagnetic transition at T N1 = 3.8 K and T N2 = 4.2 K at zero field. For Ca 3 NiNb 2 O 9 , the electric polarization in the magnetic ordered phases was clearly observed from the pyroelectric current measurements, which indicates its coexistence of magnetic ordering and ferroelectricity. 
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