Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structural and Optical Studies on Manganese doped, Modified Sodium
  Potassium Lithium Niobate Lead-free Piezoelectric Ceramics   Structural and Optical properties of the (Na0.5 K0.5)y Li 1-y NbO3 (y = 0.934
& 0.936) ceramics have been explored in terms of the X-Ray diffraction patters,
Rietveld analysis, UV-Vis spectroscopy, and Kubelka-Munk functions. Rietveld
analysis of both these structures reveals them to be tetragonal with space
group P4mm. It is found that increase in Li doping increases the optical band
gap. Presence of additional hardening dopant MnO2 is found to have a uniform
behavior for both these composition. With increasing MnO2 concentration, the
band gap decreases indicative of increase in B-site cation and O-p orbitals.
Different valences of the Mn ions and relative difference in the ionic radii of
the Mn ions and Nb ion are most likely the reason for these optical properties.

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The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: econ
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex