Phase Formation Studies of Lead(II) Copper(II) Oxotellurates: The Crystal Structures of Dimorphic PbCuTeO₅, PbCuTe₂O₆, and [Pb₂Cu₂(Te₄O₁₁)](NO₃)₂

Abstract

Two modifications of the oxotellurate(VI) PbCuTeO 5 were isolated as single crystals from product mixtures obtained from solid state reactions, whereas single crystals of the oxotellurates(IV) PbCuTe 2 O 6 and [Pb 2 Cu 2 (Te 4 O 11 )](NO 3 ) 2 were grown under hydrothermal conditions. The crystal structures of all compounds comprise of characteristic coordination polyhedra, viz. nearly square [CuO 4 ] plaquettes for divalent copper, octahedral [TeO 6 ] units for hexavalent tellurium, trigonal-pyramidal [TeO 3 ] and bisphenoidal [TeO 4 ] groups for tetravalent tellurium, and distorted [PbO x ] polyhedra for divalent lead. * Prof. Dr. M. Weil E-Mail: Matthias.Weil@tuwien.ac.at [a] ARTICLE Experimental Section Crystal Growth StudiesPbCuTeO 5 : PbCuTeO 5 was obtained via solid state reactions of Cu(NO 3 ) 2 ·2.5H 2 O (0.232 g), Pb(NO 3 ) 2 (0.334 g), and H 6 TeO 6 (0.229 g) (molar ratio 1:1:1). The starting materials were weigthed, homogenously mixed by grinding, and transferred into ceramic crucibles. The open cruicibles were placed in a furnace under the following temperature/time conditions under atmospheric conditions: t 1 = 300 min [25 Ǟ 800°C], t 2 = 3000 min [800°C] and t 3 = 1000 min [800 Ǟ 25°C]. The solid product was evaluated under a polarizing microscope to choose turquoise crystals of PbCuTeO 5 with unspecific forms for the diffraction experiments. Two different modifications of PbCuTeO 5 [monoclinic (1), triclinic (2)] could be identified by singlecrystal X-ray diffraction. According to the results of X-ray powder diffraction measurements of the bulk material, Pb 2 TeO 5 (mineral name ottoite) [6,19] was identified as the major phase and monoclinic PbCuTeO 5 as a side product.

Structural Studies on Synthetic A2−x[M2(TeO3)3]·nH2O Phases (A = Na, K, Rb, Cs; M = Mn, Co, Ni, Cu, Zn) with Zemannite-type Structures

“…As observed frequently for hydrothermal experiments (Weil & Shirkhanlou 2017;Weil et al 2019), phase mixtures were obtained in nearly all batches. The amounts of intended products, the nature of by-products and unit-cell parameters refined from powder diffraction data are listed in Table 3.…”

Crystal growth, characterization and phase transition of PbCuTe$_2$O$_6$

“…The information on structural and bulk properties of single crystals of PCTO remains inconclusive. For example, the sub-mm single crystals synthesised using the hydrothermal method report a larger lattice parameter(12.60 Å, P4 3 32) [13,14]. In addition, all single crystals also indicate a phase transition at T ∼1 K [8,15].…”

The alkali metal copper(II) oxidotellurates(IV) Li2Cu2Te3O9, Li2Cu3Te4O12, Rb2Cu3Te6O16 and Cs2Cu3Te6O16 – four new structure types

“…[9] To possibly expand our knowledge on cation-modified oxidotellurate(IV) phases, we focused on copper(II) oxidotellurates(IV) because such phases can bear interesting magnetic properties. For example, copper-(II) oxidotellurates modified by addition of Pb II [10] are reported to exhibit a three-dimensional spin liquid behavior. [11][12][13] For the current study we have selected alkali metals for cation modification.…”