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Trapping of different stages of BaTiO3 reduction with LiH
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).ORCID iD: 0000-0001-7797-7387
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).ORCID iD: 0000-0002-7156-559X
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). RWTH Aachen University, Germany.ORCID iD: 0000-0001-7975-9201
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).ORCID iD: 0000-0002-4452-1831
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2020 (English)In: RSC Advances, E-ISSN 2046-2069, Vol. 10, no 58, p. 35356-35365Article in journal (Refereed) Published
Abstract [en]

We investigated the hydride reduction of tetragonal BaTiO3 using LiH. The reactions employed molar H : BaTiO3 ratios of 1.2, 3, and 10 and variable temperatures up to 700 °C. The air-stable reduced products were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy, thermogravimetric analysis (TGA), X-ray fluorescence (XRF), and 1H magic-angle spinning (MAS) NMR spectroscopy. Effective reduction, as indicated by the formation of dark blue to black colored, cubic-phased, products was observed at temperatures as low as 300 °C. The product obtained at 300 °C corresponded to oxyhydride BaTiO∼2.9H∼0.1, whereas reduction at higher temperatures resulted in simultaneous O defect formation, BaTiO2.9−xH0.1□x, and eventually – at temperatures above 450 °C – to samples void of hydridic H. Concomitantly, the particles of samples reduced at high temperatures (500–600 °C) display substantial surface alteration, which is interpreted as the formation of a TiOx(OH)y shell, and sintering. Diffuse reflectance UV-VIS spectroscopy shows broad absorption in the VIS-NIR region, which is indicative of the presence of n-type free charge carriers. The size of the intrinsic band gap (∼3.2 eV) appears only slightly altered. Mott–Schottky measurements confirm the n-type conductivity and reveal shifts of the conduction band edge in the LiH reduced samples. Thus LiH appears as a versatile reagent to produce various distinct forms of reduced BaTiO3 with tailored electronic properties.

Place, publisher, year, edition, pages
2020. Vol. 10, no 58, p. 35356-35365
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-194826DOI: 10.1039/d0ra07276aISI: 000573815400041OAI: oai:DiVA.org:su-194826DiVA, id: diva2:1579205
Available from: 2021-07-08 Created: 2021-07-08 Last updated: 2022-09-15Bibliographically approved
In thesis
1. Structural characterization of complex inorganic materials using solid-state NMR spectroscopy
Open this publication in new window or tab >>Structural characterization of complex inorganic materials using solid-state NMR spectroscopy
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Over the past decades, advancements in technology have relied greatly on the development of new functional inorganic materials. Detailed structural characterization of these materials is key for the understanding and also prediction of chemical and physical properties. The structural characterization of complex inorganic materials is typically conducted by a combination of multiple methods. Solid-state NMR brings several advantages because it is element-specific, non-destructive and allows local-chemical-structure elucidation for composite materials, disordered and interfacial structures. This thesis focuses on the application of solid-state NMR for structural characterization of two classes of complex inorganic materials. 

Calcium phosphate cements (CPCs) have been widely applied as bone-substitution materials. The structures of the setting cements are vital for understanding their behaviors in setting and bone-regeneration processes and functions of different additives. In this thesis two types of CPCs, with different additives, were investigated. The different components in the cements could be identified and quantified with solid-state NMR. Correlation spectra were established that helped in probing the structural relationship between different phases. 

Mixed-anion perovskite compounds AB(O,X)3 (X = N, F, H, OH, etc.) have been intensively investigated because of their unique properties for different applications as introduced by the mixed anion environment for the transition metal component B. Because of the lability of hydride oxyhydrides emerged as versatile precursors for the synthesis of other mixed-anion compounds and oxynitrides are extensively investigated for their photocatalytic activity and dielectric properties. In this thesis the oxyhydrides BaTiO3-xHx and SrVO2H were synthesized and their subsequent conversions to oxynitrides were investigated. Solid-state NMR was used to probe the local chemical environments of H and N incorporated in the perovskite anion substructure. 1H NMR proved especially to be useful in the quantification of H which is very difficult to accomplish by other methods.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry, Stockholm University, 2021. p. 78
Keywords
solid-state NMR, materials characterization, inorganic materials, Calcium phosphate cements, bone-substitution materials, Mixed-anion compounds, perovskite, Oxyhydride materials, Oxynitride materials, Barium titanate, Strontium vanadate
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-194830 (URN)978-91-7911-556-2 (ISBN)978-91-7911-557-9 (ISBN)
Public defence
2021-09-27, online via Zoom, public link is available at the department website, 10:00 (English)
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Supervisors
Available from: 2021-09-02 Created: 2021-07-08 Last updated: 2021-11-22Bibliographically approved

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Guo, HuaJaworski, AleksanderMa, ZiliSlabon, AdamBacsik, ZoltanHäussermann, Ulrich

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