Influence of the Preparation Method on the Structural, Morphological and Dielectric Properties of FeNbO4 Ceramics

Abstract

In this work, iron niobate (FeNbO4) was prepared via two processes based on the sol-gel method: colloidal gel and polymeric gel. The obtained powders were submitted to heat treatments at different temperatures based on the results obtained via differential thermal analysis. The structures of the prepared samples were characterized via X-ray diffraction and the morphology was characterized via scanning electron microscopy. The dielectric measurements were performed in the radiofrequency region using the impedance spectroscopy technique and in the microwave range using the resonant cavity method. The influence of the preparation method was noticeable in the structural, morphological and dielectric properties of the studied samples. The polymeric gel method promoted the formation of monoclinic and orthorhombic iron niobate at lower temperatures. The differences in the samples’ morphology were also remarkable, both in the size and shape of the grains. The dielectric characterization revealed that the dielectric constant and the dielectric losses had the same order of magnitude and similar trends. A relaxation mechanism was identified in all the samples.

Dielectric, pyroelectric, and ferroelectric studies in (1 − x)AgNbO3–xFeNbO4 lead-free ceramics

“…The FE-SEM images indicate that as x increased from 0 to 0.1, FN was formed as a secondary phase with angular grains consistent with the XRD results. In addition, the grain boundary is clearly visible and there is heterogeneity in the grain size distribution The microstructure of the FN phase in the (1 − x )AgNbO 3 – x FeNbO 4 system is similar to the microstructure obtained in the research by Devesa et al 47 The mapping images of the ANF( x ) ceramics are shown in Fig. 7.…”

“…in the grain size distribution The microstructure of the FN phase in the (1 − x)AgNbO 3 -xFeNbO 4 system is similar to the microstructure obtained in the research by Devesa et al 47 The mapping images of the ANF(x) ceramics are shown in Fig. 7.…”

“…where w 1 , w 2 and w 3 are the mass fractions. 47 D 1 , D 2 , and D 3 are the theoretical densities of AN (6.784 g cm −3 ), 60 monoclinic FN (5.44 g cm −3 ), 41 and Ag (10.57 g cm −3 ). 61…”

“…have received a lot of attention due to their excellent electrical, magnetic, and chemical properties. 47…”

“…have received a lot of attention due to their excellent electrical, magnetic, and chemical properties. 47 Therefore, the present work reports the effects of the monoclinic (wolframite-type) FN in (1 − x)AgNbO 3 -xFeNbO 4 (0 ≤ x ≤ 0.10) solid solutions on the crystal structure, dielectric properties, phase transitions, and ferroelectric and pyroelectric properties. This study aims to manipulate the AFE/FE phase boundary to fabricate lead-free pyroelectric ceramics as well as to provide additional knowledge about (1 − x)AgNbO 3 -xFeNbO 4 ceramics and assess their performance in pyroelectric applications.…”