Abstract
Bismuth germanate (Bi12GeO20) ceramics were produced using modified Pechini route, and the synthesis parameters, crystalline phases, microstructure, and sintering conditions were investigated.Bi12GeO20powders with submicrometric particle sizes were investigated for calcination temperatures from 400 to 600°C, with soaking times of 1 h and 5 h. Controlling the synthesis parameters, dense ceramics with two different grain sizes of 3.4 ± 0.5 µm and 5.7 ± 0.8 µm could be produced after sintering at 750°C/1 h. The electric and dielectric properties of these ceramics were determined by impedance spectroscopy (IS). From the results, it was concluded that the dielectric permittivity measured at high frequencies is insensitive to the grain size, while the AC dark conductivity presents a noticeable dependency on this feature. This behaviour was discussed on the basis of a Maxwell-Wagner interfacial relaxation, whose intensity depends directly on the volume fraction of grain boundaries in the sample.
Highlights
Bismuth germanate (Bi12GeO20) belongs to a class of materials known as sillenites with general formula Bi12MO20, where M represents a tetravalent ion or a combination of ions yielding average charge 4+ [1, 2]
In this work impedance spectroscopy (IS) was utilized to determine the AC conductivity and dielectric permittivity of the bismuth germanate ceramics obtained by modified Pechini method, comparing the obtained parameters with those reported in the literature and investigating the influence of the grain size on these properties [9, 17,18,19,20]
For the samples calcined at 450∘C/1 h, single phase was obtained after sintering the ceramic bodies
Summary
Bismuth germanate (Bi12GeO20) belongs to a class of materials known as sillenites with general formula Bi12MO20, where M represents a tetravalent ion or a combination of ions yielding average charge 4+ [1, 2]. Pechini process has emerged as a powerful method to obtain nanocrystalline powders in several compositions. This synthesis route allows the formation of a polymeric net (resin) containing the metallic ions homogeneously distributed. In this work impedance spectroscopy (IS) was utilized to determine the AC conductivity and dielectric permittivity of the bismuth germanate ceramics obtained by modified Pechini method, comparing the obtained parameters with those reported in the literature and investigating the influence of the grain size on these properties [9, 17,18,19,20]. Structural and microstructure characterization of the powders and dense ceramics are presented and discussed
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