14.10.2008

Na₃Ga₃Te₂O₁₂: Synthesis, single crystal structure and characterization

^aDepartment of Chemistry and Center for Materials Chemistry, University of Houston, 136 Fleming Building, Houston, TX 77204-5003, USA

Received 5 November 2007;

revised 13 December 2007;

accepted 8 January 2008.

Available online 25 January 2008.

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Abstract

Colorless, polyhedral single crystals of Na₃Ga₃Te₂O₁₂ have been synthesized for the first time by supercritical hydrothermal techniques using NaOH, Ga₂O₃, TlNO₃ and TeO₂ as reagents. Na₃Ga₃Te₂O₁₂ was characterized by single-crystal and powder X-ray diffractions, IR, Raman, UV–vis diffuse reflectance spectroscopies and thermogravimetric analysis. Na₃Te₂Ga₃O₁₂ crystallizes in the cubic space group Ia-3d (No. 230) with a = 12.3604(14) Å, V = 1888.4(4) Å³, and Z = 8. Na₃Ga₃Te₂O₁₂ exhibits a garnet structure-type with the Te⁶⁺ and Ga³⁺ cations occupying the octahedral and tetrahedral sites, respectively.

Graphical abstract

Keywords: Supercritical hydrothermal synthesis; Tellurium; Garnet; Three-dimensional structure

Article Outline

1. Introduction
2. Experimental 2.1. Synthesis 2.2. Crystallographic determination 2.3. Spectroscopic characterization 2.4. Thermogravimetric analysis 2.5. SEM imaging
3. Results and discussion 3.1. Structure 3.2. Infrared and Raman spectroscopies 3.3. UV–vis diffuse reflectance spectroscopy 3.4. Thermogravimetric analysis
Acknowledgements
Appendix. Supporting information
References

Fig. 1. Ball-and-stick diagrams showing (a) the Te–O–Ga–O building unit (16-membered ring) viewed on the ab-plane and (b) one layer of Na₃Ga₃Te₂O₁₂ viewed on the bc-plane.

Fig. 2. Polyhedral (Te⁶⁺/Ga³⁺) representation of Na₃Ga₃Te₂O₁₂ viewed down the [11−1] direction. The Na⁺ atoms have been omitted for clarity.

Fig. 3. Scanning electron micrographs of some Na₃Ga₃Te₂O₁₂ crystals.

Table 1.

Crystal data for Na₃Ga₃Te₂O₁₂

^a R(F) = ∑||F_o| − |F_c||/Σ|F_o|.
^b R_w(F_o²) = [∑w(F_o² − F_c²)²/Σw(F_o²)²]^1/2.

Table 2.

Atomic coordinates for Na₃Ga₃Te₂O₁₂

^a U_eq is defined as one third of the trace of the orthogonalized U_ij tensor.

Table 4.

Comparison of lattice constants (a, Å) among similar A₃B₃M₂O₁₂ garnets (M = Te⁶⁺, W⁶⁺)

^a Data from (presumably) powder X-ray diffraction; no standard deviation provided.