BaAg2-xAs2 belongs to the abundant intermetallic ThCr2Si2 crystal structure type, a large group of about 700 layered ternary compounds. It crystallizes in the tetragonal I4/mmm space group and has a notable transition metal deficiency. Motivating this study is the similarity in transport properties of BaAg2-xAs2 and previously reported ThCr2Si2 type materials that have interesting superconductive, thermoelectric, and magnetic behaviors. In this current work, the synthesis of polycrystalline bulk powder and large single crystals of BaAg2-xAs2 was developed which allows for control of the Ag vacancy concentration. Characterization of the electrical resistivity, thermal conductivity, and Seebeck coefficient indicate a possible low-temperature structural transition, emphasized by a kink in the temperature-dependent properties. The kink feature in the resistivity can be modulated as a result of varying the silver vacancy concentration. Differential scanning calorimetry experiments show the crystallization temperature of the phase varies with silver deficiency degree and is highly dependent on the concentration of Ba-Ag-As reactants in bismuth flux. Further increase of the structural complexity can be achieved by the introduction of main group elements, Ga or In triels. The novel Ba4Ag2.3In1.7As8 and Ba4AgGa5As8 compounds were synthesized as a result of initially targeting BaAgTrAs2 compositions. Ba4Ag2.3In1.7As8 crystallizes in the monoclinic P21/m spacegroup and Ba4AgGa5As8 crystallizes in the non-centrosymmetric orthorhombic Iba2 space group. Ba4Ag2.3In1.7As8 (~BaAg0.5In0.5As2) is a layered material, similar to the tetragonal LaCuSb2 structure, with the cation layered in between edge-sharing (Ag,In)As4/2 tetrahedra and a layer composed of 1D cis-trans chains of As atoms. Ba4AgGa5As8 is a 3D material with the cation located in the voids of the 3D framework composed of distorted corner and edge-sharing (Ga,Ag)As4/2 tetrahedra. Crystal growth and bulk powder synthesis of Ba4Ag2.3In1.7As8 has been optimized. Resistivity property characterization indicated the metallic nature of the Ba4Ag2.3In1.7As8 material.

Synthesis, structure, and properties of novel Ba-M-As phases (M = Ag, Ag/Ga, Ag/In)

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