Structural ordering and dielectric properties of Ba3CaNb2O9-based microwave ceramics

Ceramics International, 42(2016)18087–18093

10 de setembro de 2016 CDMF Artigo, Meio Ambiente 0

EDS-elemental-mapping-for — Fig.: EDS elemental mapping for Ba (a),Ca (b),Nb (c)O (d), and their colors uper position (e) toward the SEM micrograph on the left of the 32h BCaNO ceramic (scale bars 1mm).

Writers: RODRIGUES, J. E. F. S.; CASTRO, P. J.; PIZANI, P. S.; CORRER, Wagner Rafael; HERNANDES, Antônio Carlos.

Keywords: Ba(Ca_1/3Nb_2/3)O₃; 1:2 ordered perovskite; Cation ordering; Microwave dielectric properties; Dielectric resonator

Abstract: Ba₃CaNb₂O₉ is a 1:2 ordered perovskite which presents a trigonal cell within the D_3d³ space group. Dense ceramics of Ba₃CaNb₂O₉ were prepared by the solid-state reaction route, and their microwave dielectric features were evaluated as a function of the sintering time. From Raman spectroscopy, by using group-theory calculations, we were able to recognize the coexistence of the 1:1 and 1:2 ordering types in all samples, in which increasing the sintering time tends to reduce the 1:1 domain, leading to an enhancement of the unloaded quality factor. We concluded that this domain acts as a lattice vibration damping, consequently raising the dielectric loss at microwave frequencies. The best microwave dielectric parameters were determined in ceramics sintered at 1500 °C for 32h: ε′ ~ 43; Q_u×f_r = 15,752 GHz; τ_f ~ 278 ppm °C⁻¹.

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