Phase Stability, Structures and Properties of the (Bi2)m(Bi2Te3)n Natural Superlattices

Abstract

The phase stability of the (Bi2)m(Bi2Te3)n natural superlattices has been investigated through the low temperature solid state synthesis of a number of new binary BixTe1-x compositions. Powder X-ray diffraction revealed that an infinitely adaptive series forms for 0.44 < x < 0.70, while an unusual 2-phase region with continuously changing compositions is observed for 0.41 < x < 0.43. For x > 0.70, mixtures of elemental Bi and an almost constant composition (Bi2)m(Bi2Te3)n phase are observed. Rietveld analysis of synchrotron X-ray powder diffraction data collected on Bi2Te (m = 2, n = 1) revealed substantial interchange of Bi and Te between the Bi2 and Bi2Te3 blocks, demonstrating that the block compositions are variable. All investigated phase pure compositions are degenerate semiconductors with low residual resistivity ratios and moderate positive magnetoresistances (R/R0 = 1.05 in 9 T). The maximum Seebeck coefficient is +80 muV K-1 for x = 0.63, leading to an estimated thermoelectric figure of merit, zT = 0.2 at 250 K.

arXiv commentaccepted to a special issue on thermoelectric materials in the Journal of Solid State Chemistry

References in corpus (4)

• A topological Dirac insulator in a quantum spin Hall phase : Experimental observation of first strong topological insulator
• The development of ferromagnetism in the doped topological insulator Bi2-xMnxTe3
• The structures and thermoelectric properties of the infinitely adaptive series (Bi2)m(Bi2Te3)n
• Ferromagnetism below 10 K in Mn doped BiTe

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• Decoding Thermal Stability: In situ Insights into Phase Controlled Phosphine-free Colloidal Bi-Te Nanosheets