Micro far-infrared dielectric response of lanthanide orthotantalates for applications in microwave circuitry

JOURNAL OF ALLOYS AND COMPOUNDS

卷:693

Article

Dias, Anderson¹  Siqueira, Kisla P. F.¹  Moreira, Roberto L.² 

[1] Univ Fed Ouro Preto, Dept Quim, Campus Morro Cruzeiro,ICEB 2,Sala 67, BR-35400000 Ouro Preto, MG, Brazil

[2] Univ Fed Minas Gerais, ICEx, Dept Fis, CP 702, BR-30123970 Belo Horizonte, MG, Brazil

关键词: Ceramics;    Infrared reflectivity;    Rare earth;    Microwave;    Dielectric resonators;    Orthotantalates;   

DOI  :  10.1016/j.jallcom.2016.10.077

来源: Elsevier

【 摘 要 】

Lanthanide orthotantalates LnTaO(4) (Ln - La, Nd, Dy and Lu) were synthesized by solid-state reactions at 1300 degrees 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: P2(1)/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 MW dielectric response among the investigated LnTaO(4) (epsilon(r) = 21.2 and estimated Q(u) x f approximate to 77 THz), followed by DyTaO4 (epsilon(r) = 19.9 and Q(u) x f approximate to 75 THz), NdTaO4 (epsilon(r) = 18.7 and Q(u) x f approximate to 55 THz), and LuTaO4 (epsilon(r) - 16.2 and Q(u) x f approximate to 60 THz). (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

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