Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Controlled synthesis of the antiperovskite oxide superconductor
  Sr$_{3-x}$SnO   A large variety of perovskite oxide superconductors are known, including some
of the most prominent high-temperature and unconventional superconductors.
However, superconductivity among the oxidation state inverted material class,
the antiperovskite oxides, was reported just recently for the first time. In
this superconductor, Sr$_{3-x}$SnO, the unconventional ionic state Sn$^{4-}$ is
realized and possible unconventional superconductivity due to a band inversion
has been discussed. Here, we discuss an improved facile synthesis method,
making it possible to control the strontium deficiency in Sr$_{3-x}$SnO.
Additionally, a synthesis method above the melting point of Sr$_{3}$SnO is
presented. We show temperature dependence of magnetization and electrical
resistivity for superconducting strontium deficient Sr$_{3-x}$SnO
($T_{\mathrm{c}}$ ~ 5 K) and for Sr$_{3}$SnO without a superconducting
transition down to 0.15 K. Further, we reveal a significant effect of strontium
raw material purity on the superconductivity and achieve 40% increased
superconducting volume fraction (~100%) compared to the highest value reported
so far. More detailed characterisation utilising powder X-ray diffraction and
energy-dispersive X-ray spectroscopy show that a minor cubic phase, previously
suggested to be a Sr$_{3-x}$SnO, is SrO. The improved characterization and
controlled synthesis reported herein enable detailed investigations on the
superconducting nature and its dependency on the strontium deficiency in
Sr$_{3-x}$SnO.

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The categories of this paper are: astro-ph
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ph
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The categories of this paper are: math