Električna i magnetska svojstva dvostrukih i trostrukih volframatnih i teluratnih perovskita

doctoral thesis

• Title (english): Electrical and magnetic properties of double and triple tungsten- and tellurium-based perovskites
• Author: Jelena Bijelić
• Mentor: Igor Đerđ (mentor)
• Committee member: Vladimir Stilinović (predsjednik povjerenstva)
• Committee member: Jasminka Popović (član povjerenstva)
• Committee member: Marijana Jurić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Chemistry); Zagreb
• Defense date and country: 2021-05-26, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry
• Universal decimal classification (UDC): 54 - Chemistry. Crystallography. Mineralogy

Abstract

Modificiranom sol-gel sintezom pripravljeni su trostruki perovskiti A3(Fe/Co)2(W/Te)O9 i dvostruki perovskiti A2Ni(Te/W)O6 (A = Sr2+, Ba2+). Sintetski mehanizam ispitan je cikličkom voltametrijom i UV/Vis spektroskopijom tijekom sinteze u otopini, a tijekom kalcinacije in situ temperaturno ovisnom rentgenskom difrakcijom u prahu (in situ PXRD). PrireĎeni su spojevi detaljno strukturno i morfološki okarakterizirani rentgenskom difrakcijom u prahu (PXRD), Ramanovom spektroskopijom, pretraţnom elektronskom mikroskopijom (SEM), transmisijskom elektronskom mikroskopijom visoke razlučivosti (HRTEM) i elektronskom difrakcijom na odabranoj površini (SAED). Kemijski sastav istraţen im je energijski razlučujućom rentgenskom spektroskopijom (EDX) i rentgenskom fotoelektronskom spektroskopijom (XPS). Dobiveni su nanokristalni oblici istraţivanih spojeva unatoč relativno visokim temperaturama kalcinacije, u rasponu prosječne veličine kristalita od 20 do 90 nm. Dobivenim sustavima su ispitana magnetska i električna svojstva, te je uočeno kako pokazuju fero-/feri- i antiferomagnetsko ureĎenje s velikim vrijednostima dielektričnih konstanti. Vrijednosti dielektričnih konstanti i dielektričnih gubitaka opadaju porastom frekvencije što je opisano Maxwell-Wagnerovim modelom.

Abstract (english)

Triple perovskites A3(Fe/Co)2(W/Te)O9 and double perovskites A2Ni(Te/W)O6 (A = Sr2+, Ba2+) have been prepared using modified sol-gel route. The synthesis mechanism was investigated by cyclic voltammetry and UV/Vis spectroscopy during solution synthesis by temperature-dependent X-ray diffraction (in situ PXRD) during calcination. Prepared compounds were structurally and morphologically characterized by powder X-ray diffraction (PXRD), Raman spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and selected area elctron diffraction (SAED). Chemical composition was inspected using energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Nanocrystalline forms of investigated compounds were obtained with average crystallite sizes in range from 20 to 90 nm despite relatively high calcination temperatures. Magnetic and electrical properties of obtained compounds were investigated revealing fero-/feri- and antiferromagnetic otdering with high relatively high values of dielectric constants. Dielectric constant and loss values decrease with the increase of frequency which is described by Maxwell-Wagner model.

• Keywords: dvostruki perovskiti; trostruki perovskiti; strukturna i morfološka karakterizacija; električna svojstva; elektronika; magnetska svojstva; nanomaterijali perovskita
• Keywords (english): double perovskites; triple perovskites; structural and morphological characterization; electrical properties; electronics; magnetic properties; perovskite nanomaterials
• Language: croatian
• URN:NBN: urn:nbn:hr:217:074171
• Promotion: 2021
• Project: Number: IP-2016-06-3115; Title: Istraživanje složenih multiferoičnih materijala pripravljenih metodama otopinske kemije; Title: Solution chemistry routes towards complex multiferroic materials; Acronym: SOLFERROMAT; Leader: Igor Đerđ; Jurisdiction: Croatia; Funder: HRZZ; Funding stream: IP
• Study programme: Title: Doctoral study in chemistry; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje prirodnih znanosti, polje kemija (doktor/doktorica znanosti, područje prirodnih znanosti, polje kemija)
• Type of resource: Text
• Extent: 181 str. ; 30 cm
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-05-28 12:03:05