First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar

Crystal structures of α-Bi2O3 and β-Bi2O3 were calculated using Cambridge serial total energy package (CASTEP) based on the first-principles plane-wave ultrasoft pseudopotential method within local density approximation (LDA) and generalized gradient approximation (GGA) together with Perdew–Burke–Er...

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主要作者:	Azhar, Nurul Syahirah
格式:	Thesis
语言:	English
出版:	2021
主题:	Electric conductivity
在线阅读:	https://ir.uitm.edu.my/id/eprint/60538/1/60538.pdf
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record_format	uketd_dc
spelling	my-uitm-ir.605382022-05-30T04:46:22Z First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar 2021-08 Azhar, Nurul Syahirah Electric conductivity Crystal structures of α-Bi2O3 and β-Bi2O3 were calculated using Cambridge serial total energy package (CASTEP) based on the first-principles plane-wave ultrasoft pseudopotential method within local density approximation (LDA) and generalized gradient approximation (GGA) together with Perdew–Burke–Ernzerhof (GGA-PBE) and Perdew–Burke–Ernzerhof revised for solid (GGA-PBEsol). The structural parameter of α-Bi2O3 and β-Bi2O3 are in good agreement with previous experimental and theoretical data (Matsumoto, Koyama, Tanaka 2010). The DFT+U method gives the correction due to the underestimate results from DFT as compared to the experimental value. All of the polymorphs were calculated for the total density of states (TDOS) and the partial density of states (PDOS) of Bi, O atoms. Density of states exhibits hybridization of Bi 6s and O 2p orbitals and the calculated charge density exhibit the ionic character in the chemical bonding of this compound. The narrowed band gap (Eg) and red shift of light absorption edge are responsible for the photocatalytic activity of β-Bi2O3 for water splitting application. β-Bi2O3 is the best structure among these polymorphs for the photocatalyst application based on the calculated optical properties such as optical absorption and electron energy loss function. Hence, β-Bi2O3 polymorph was used in the modification of Bi2O3 by doping method. Lanthanide (Ln) elements; Europium (Eu), Gadolinium (Gd) and Erbium (Er) as Ln dopants were determined. The Eu- and Gd-doped Bi2O3 were observed to have lower band gaps compared to pure Bi2O3. The band gap of Er- Bi2O3 was slightly higher than pure Bi2O3 but it can be related to the results of the absorption coefficient. The presence of Ln 4f states in Ln-doped Bi2O3 can be seen from the Density of States (DOS) which explained the narrowing of the band gap. Among the Ln-doped Bi2O3 (Ln = Eu, Gd and Er), the shifting of light towards a longer wavelength spectrum is obtained from the Gd-doped Bi2O3. Overall, the first-principles study in this work from the deepest level of atomic-scale can explain the law of physics from the properties of studied materials and improve the understanding of Bi2O3 semiconductor as a photocatalyst. 2021-08 Thesis https://ir.uitm.edu.my/id/eprint/60538/ https://ir.uitm.edu.my/id/eprint/60538/1/60538.pdf text en public masters Universiti Teknologi MARA Faculty of Applied Sciences Ali, Ab Malik Marwan (Prof. Dr.)
institution	Universiti Teknologi MARA
collection	UiTM Institutional Repository
language	English
advisor	Ali, Ab Malik Marwan (Prof. Dr.)
topic	Electric conductivity
spellingShingle	Electric conductivity Azhar, Nurul Syahirah First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar
description	Crystal structures of α-Bi2O3 and β-Bi2O3 were calculated using Cambridge serial total energy package (CASTEP) based on the first-principles plane-wave ultrasoft pseudopotential method within local density approximation (LDA) and generalized gradient approximation (GGA) together with Perdew–Burke–Ernzerhof (GGA-PBE) and Perdew–Burke–Ernzerhof revised for solid (GGA-PBEsol). The structural parameter of α-Bi2O3 and β-Bi2O3 are in good agreement with previous experimental and theoretical data (Matsumoto, Koyama, Tanaka 2010). The DFT+U method gives the correction due to the underestimate results from DFT as compared to the experimental value. All of the polymorphs were calculated for the total density of states (TDOS) and the partial density of states (PDOS) of Bi, O atoms. Density of states exhibits hybridization of Bi 6s and O 2p orbitals and the calculated charge density exhibit the ionic character in the chemical bonding of this compound. The narrowed band gap (Eg) and red shift of light absorption edge are responsible for the photocatalytic activity of β-Bi2O3 for water splitting application. β-Bi2O3 is the best structure among these polymorphs for the photocatalyst application based on the calculated optical properties such as optical absorption and electron energy loss function. Hence, β-Bi2O3 polymorph was used in the modification of Bi2O3 by doping method. Lanthanide (Ln) elements; Europium (Eu), Gadolinium (Gd) and Erbium (Er) as Ln dopants were determined. The Eu- and Gd-doped Bi2O3 were observed to have lower band gaps compared to pure Bi2O3. The band gap of Er- Bi2O3 was slightly higher than pure Bi2O3 but it can be related to the results of the absorption coefficient. The presence of Ln 4f states in Ln-doped Bi2O3 can be seen from the Density of States (DOS) which explained the narrowing of the band gap. Among the Ln-doped Bi2O3 (Ln = Eu, Gd and Er), the shifting of light towards a longer wavelength spectrum is obtained from the Gd-doped Bi2O3. Overall, the first-principles study in this work from the deepest level of atomic-scale can explain the law of physics from the properties of studied materials and improve the understanding of Bi2O3 semiconductor as a photocatalyst.
format	Thesis
qualification_level	Master's degree
author	Azhar, Nurul Syahirah
author_facet	Azhar, Nurul Syahirah
author_sort	Azhar, Nurul Syahirah
title	First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar
title_short	First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar
title_full	First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar
title_fullStr	First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar
title_full_unstemmed	First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar
title_sort	first-principles study on structural, electronic and optical properties of ln-doped bi2o3 (ln = eu, gd and er) as a photocatalyst / nurul syahirah azhar
granting_institution	Universiti Teknologi MARA
granting_department	Faculty of Applied Sciences
publishDate	2021
url	https://ir.uitm.edu.my/id/eprint/60538/1/60538.pdf
_version_	1783735141421547520

First-principles study on structural, electronic and optical properties of ln-doped Bi2O3 (Ln = Eu, Gd AND Er) as a photocatalyst / Nurul Syahirah Azhar

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