Synthesis, Crystal and Electronic Structures, and Properties of the New Pnictide Semiconductors A₂CdPn₂ (A = Ca, Sr, Ba, Eu; Pn = P, As)

Citations Over TimeTop 17% of 2011 papers

Abstract

A series of ternary Zintl phases, Ca(2)CdP(2), Ca(2)CdAs(2), Sr(2)CdAs(2), Ba(2)CdAs(2), and Eu(2)CdAs(2), have been synthesized through high temperature metal flux reactions, and their structures have been characterized by single-crystal X-ray diffraction. They belong to the Yb(2)CdSb(2) structure type and crystallize in the orthorhombic space group Cmc2(1) (No. 36, Z = 4) with cell dimensions of a = 4.2066(5), 4.3163(5), 4.4459(7), 4.5922(5), 4.4418(9) Å; b = 16.120(2), 16.5063(19), 16.904(3), 17.4047(18), 16.847(4) Å; c = 7.0639(9), 7.1418(8), 7.5885(11), 8.0526(8), 7.4985(16) Å for Ca(2)CdP(2) (R1 = 0.0152, wR2 = 0.0278), Ca(2)CdAs(2) (R1 = 0.0165, wR2 = 0.0290), Sr(2)CdAs(2) (R1 = 0.0238, wR2 = 0.0404), Ba(2)CdAs(2) (R1 = 0.0184, wR2 = 0.0361), and Eu(2)CdAs(2) (R1 = 0.0203, wR2 = 0.0404), respectively. Among these, Ca(2)CdAs(2) was found to form with another closely related structure, depending on the experimental conditions--monoclinic space group Cm (No. 8, Z = 10) with lattice constants a = 21.5152(3) Å, b = 4.30050(10) Å, c = 14.3761(2) Å and β = 110.0170(10)° (R1 = 0.0461, wR2 = 0.0747). UV/vis optical absorption spectra for both forms of Ca(2)CdAs(2) show band gaps on the order of 1.0 eV, suggesting semiconducting properties, which have also been confirmed through electronic band structure calculations based on the density-functional theory. Results from differential scanning calorimetry measurements probing the thermal stability and phase transitions in the two Ca(2)CdAs(2) polymorphs are discussed. Magnetic susceptibility measurements for Eu(2)CdAs(2), indicating divalent Eu(2+) cations, are presented as well.

Related Papers

• → Polymorphism and History of 2-Dimethylsufuranylidene-1,3-indanedione (YLID)(2008)14 cited
• → Another orthorhombic crystal modification of n-hexatriacontane and its vibrational spectra(1980)41 cited
• → First principles calculations of electronic structures for orthorhombic and monoclinic Cu₄SnS₄(2013)7 cited
• → Crystal and molecular structures of the monoclinic and orthorhombic modifications ofo-bromophenylazocarbamide(1971)3 cited
• → ChemInform Abstract: Controlled Synthesis of the Monoclinic and Orthorhombic Polymorphs of Sr₂SiO₄ Activated with Ce3+ or Eu2+.(2016)