Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems

Herein we report the synthesis and characterisation of novel pyrochlores in the Bi2O3-Fe2O3-M2O5 (M = Nb, Ta and Sb) ternary systems. Bi-containing pyrochlores are of great research interest to its low firing and interesting electrical properties. The subsolidus cubic pyrochlore phases with the prop...

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Main Author:	Jusoh, Farah Aishah
Format:	Thesis
Language:	English English
Published:	2020
Subjects:	Anions Ternary system
Online Access:	http://psasir.upm.edu.my/id/eprint/112613/1/FS%202020%2053%20-%20IR.pdf
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spelling	my-upm-ir.1126132024-09-30T03:02:53Z Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems 2020-12 Jusoh, Farah Aishah Herein we report the synthesis and characterisation of novel pyrochlores in the Bi2O3-Fe2O3-M2O5 (M = Nb, Ta and Sb) ternary systems. Bi-containing pyrochlores are of great research interest to its low firing and interesting electrical properties. The subsolidus cubic pyrochlore phases with the proposed formula of Bi3.36Fe2.08+xM2.56-xO14.56-x (M = Nb, Ta and Sb) were prepared via conventional solid-state method in the temperature range 925 to 975 ˚C over 2 days. The solid solution mechanism was proposed to be a one-to-one replacement of M5+ by Fe3+ with considerable oxygen non-stoichiometry in the pyrochlore structure. The solid solution limits, as confirmed by x-ray diffraction (XRD) analysis, were (-0.24 ≤ x ≤ 0.48), (-0.32 ≤ x ≤ 0.48) and (0 ≤ x ≤ 0.64) for the Nb-, Ta- and Sb-analogues, respectively. These prepared samples crystallised in a cubic structure with a space group of Fd3m (No. 277). The refined lattice parameters, a = b = c of these pyrochlores showed no significant difference with increasing Fe3+ content and their values were found to be in the range 10.5065 (4)-10.5079 (5) Å, 10.4979 (8)-10.5033 (1) Å and 10.4284 (8)-10.4513 (8) Å for the Nb-, Ta- and Sb-analogues, respectively. The crystallite sizes calculated using both Scherrer and Williamson-Hall methods were found to be in the range 46.3-78.1 nm. Meanwhile, the surface morphologies of these pyrochlores showed a broad distribution of the grain size. All samples are confirmed to have correct chemical stoichiometries by inductively coupled plasma optical emission spectroscopy (ICP-OES). The thermal analyses showed all samples were thermally stable as neither phase transition nor weight loss was observed. On the other hand, five phonon modes due to the metal-oxygen bonds were found in the Fourier transform infrared spectroscopy (FT-IR) spectra of Bismuth Iron Niobate (BFN) and Bismuth Iron Tantalate (BFT) series; whilst, only three infrared-active phonon modes were detected in the Bismuth Iron Antimonate (BFS) solid solution. All the pyrochlores exhibited moderate dielectric constants in the range ~23-150 and low dielectric losses, in the order of 10-1 at 1 MHz and ~30 ˚C. The Arrhenius conductivity plots of these Nb-, Ta- and Sb- pyrochlore series showed a linear and reversible characteristic over the heat-cool cycle. In addition, the specific capacitances of all samples were determined by cyclic voltammetry (CV) and galvanostatic charge-discharged (GCD). The calculated specific capacitances by both methods indicated an insignificant variation among samples within the series as the values were less influenced by the Fe content. Anions Ternary system 2020-12 Thesis http://psasir.upm.edu.my/id/eprint/112613/ http://psasir.upm.edu.my/id/eprint/112613/1/FS%202020%2053%20-%20IR.pdf text en public masters Universiti Putra Malaysia Anions Ternary system Tan, Kar Ban English
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English English
advisor	Tan, Kar Ban
topic	Anions Ternary system
spellingShingle	Anions Ternary system Jusoh, Farah Aishah Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems
description	Herein we report the synthesis and characterisation of novel pyrochlores in the Bi2O3-Fe2O3-M2O5 (M = Nb, Ta and Sb) ternary systems. Bi-containing pyrochlores are of great research interest to its low firing and interesting electrical properties. The subsolidus cubic pyrochlore phases with the proposed formula of Bi3.36Fe2.08+xM2.56-xO14.56-x (M = Nb, Ta and Sb) were prepared via conventional solid-state method in the temperature range 925 to 975 ˚C over 2 days. The solid solution mechanism was proposed to be a one-to-one replacement of M5+ by Fe3+ with considerable oxygen non-stoichiometry in the pyrochlore structure. The solid solution limits, as confirmed by x-ray diffraction (XRD) analysis, were (-0.24 ≤ x ≤ 0.48), (-0.32 ≤ x ≤ 0.48) and (0 ≤ x ≤ 0.64) for the Nb-, Ta- and Sb-analogues, respectively. These prepared samples crystallised in a cubic structure with a space group of Fd3m (No. 277). The refined lattice parameters, a = b = c of these pyrochlores showed no significant difference with increasing Fe3+ content and their values were found to be in the range 10.5065 (4)-10.5079 (5) Å, 10.4979 (8)-10.5033 (1) Å and 10.4284 (8)-10.4513 (8) Å for the Nb-, Ta- and Sb-analogues, respectively. The crystallite sizes calculated using both Scherrer and Williamson-Hall methods were found to be in the range 46.3-78.1 nm. Meanwhile, the surface morphologies of these pyrochlores showed a broad distribution of the grain size. All samples are confirmed to have correct chemical stoichiometries by inductively coupled plasma optical emission spectroscopy (ICP-OES). The thermal analyses showed all samples were thermally stable as neither phase transition nor weight loss was observed. On the other hand, five phonon modes due to the metal-oxygen bonds were found in the Fourier transform infrared spectroscopy (FT-IR) spectra of Bismuth Iron Niobate (BFN) and Bismuth Iron Tantalate (BFT) series; whilst, only three infrared-active phonon modes were detected in the Bismuth Iron Antimonate (BFS) solid solution. All the pyrochlores exhibited moderate dielectric constants in the range ~23-150 and low dielectric losses, in the order of 10-1 at 1 MHz and ~30 ˚C. The Arrhenius conductivity plots of these Nb-, Ta- and Sb- pyrochlore series showed a linear and reversible characteristic over the heat-cool cycle. In addition, the specific capacitances of all samples were determined by cyclic voltammetry (CV) and galvanostatic charge-discharged (GCD). The calculated specific capacitances by both methods indicated an insignificant variation among samples within the series as the values were less influenced by the Fe content.
format	Thesis
qualification_level	Master's degree
author	Jusoh, Farah Aishah
author_facet	Jusoh, Farah Aishah
author_sort	Jusoh, Farah Aishah
title	Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems
title_short	Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems
title_full	Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems
title_fullStr	Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems
title_full_unstemmed	Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems
title_sort	synthesis and electrical properties of novel pyrochlores in the bi₂o₃-fe₂o₃-m₂o₅ (m = nb, ta and sb) ternary systems
granting_institution	Universiti Putra Malaysia
publishDate	2020
url	http://psasir.upm.edu.my/id/eprint/112613/1/FS%202020%2053%20-%20IR.pdf
_version_	1811767789003735040

Synthesis and electrical properties of novel pyrochlores in the Bi₂O₃-Fe₂O₃-M₂O₅ (M = Nb, Ta and Sb) ternary systems

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