Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structural position and oxidation state of nickel in SrTiO3   The properties of Ni-doped strontium titanate are studied using X-ray
diffraction and XAFS spectroscopy. It is shown that regardless of the
preparation conditions, the SrTi1-xNixO3 solid solution and the NiTiO3 phase
are the most stable phases which can coexist. According to the EXAFS data, in
the single-phase sample of SrTi0.97Ni0.03O3, the Ni atoms substitute for the Ti
ones and are on-center. The distortion of the oxygen octahedra is not observed.
The XANES spectra analysis shows that the oxidation state of nickel in NiTiO3
is 2+, and in the SrTi1-xNixO3 solid solution it is close to 4+. It is shown
that the strongest light absorption in doped samples is associated with the
presence of tetravalent nickel in the SrTi1-xNixO3 solid solution. This doping
seems the most promising one for solar energy converters that exploit the bulk
photovoltaic effect.

2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc