Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phase-separation control of K$_x$Fe$_{2-y}$Se$_2$ superconductor through
  rapid-quenching process   K$_x$Fe$_{2-y}$Se$_2$ exhibits an iron-vacancy ordering at $T_{\rm s}
{\sim}270{\deg}$C and separates into two phases: a minor superconducting
(iron-vacancy-disordered) phase and a major non-superconducting
(iron-vacancy-ordered) phase. The microstructural and superconducting
properties of this intermixture can be tuned by an appropriate control of the
quenching process through $T_{\rm s}$. A faster quenching rate leads to a finer
microstructure and a suppression of formation of the non-superconducting phase
by up to 50%. Nevertheless, such a faster cooling rate does induce a monotonic
reduction in the superconducting transition temperature (from 30.7 K down to
26.0 K) and, simultaneously, a decrease in the iron content within the
superconducting phase such that the compositional ratio changed from
K$_{0.35}$Fe$_{1.83}$Se$_2$ to K$_{0.58}$Fe$_{1.71}$Se$_2$.

28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc