Micro far-infrared dielectric response of lanthanide orthotantalates for applications in microwave circuitry.
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2017
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Lanthanide orthotantalates LnTaO4 (Ln ¼ La, Nd, Dy and Lu) were synthesized by solid-state reactions at
1300 C leading to well crystallized single-phase materials. XRD and infrared spectroscopic investigations
showed that the samples exhibited three different monoclinic crystal structures depending on the
lanthanide ion: P21/c (for La), I2/a (for Nd) and P2/a (for Dy and Lu). For LaTaO4, 21 polar modes could be
depicted from the unpolarized infrared reflectivity spectrum, while group theory tools foreseen 33
infrared-active modes e the absent mode are likely hidden by accidental degeneracy. The smaller lanthanides
(Nd, Dy and Lu) exhibited all the 15 predicted infrared-active bands, in perfect agreement with
group-theory calculations, despite the mixing of polarization symmetry due to the polycrystalline nature
of the samples. The intrinsic (infrared) dielectric properties were determined for all samples indicating
that these orthotantalate ceramics could be candidates for microwave (MW) circuitry applications.
LaTaO4 ceramics exhibited the best MWdielectric response among the investigated LnTaO4 ( 3 r ¼ 21.2 and
estimated Qu f z 77 THz), followed by DyTaO4 ( 3 r ¼ 19.9 and Qu f z 75 THz), NdTaO4 ( 3 r ¼ 18.7 and
Qu f z 55 THz), and LuTaO4 ( 3 r ¼ 16.2 and Qu f z 60 THz).
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Ceramics, Microwave, Rare earth, Infrared reflectivity
Citação
DIAS, A.; SIQUEIRA, K. P. F.; MOREIRA, R. L. Micro far-infrared dielectric response of lanthanide orthotantalates for applications in microwave circuitry. Journal of Alloys and Compounds, v. 693, p. 1243-1249, fev. 2017. Disponível em: <http://www.sciencedirect.com/science/article/pii/S0925838816331863> Acesso em: 15 set. 2017