Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phase Stability, Structures and Properties of the (Bi2)m(Bi2Te3)n
  Natural Superlattices   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.

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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ex
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The categories of this paper are: astro-ph
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The categories of this paper are: plasm-ph