Utjecaj kristalizacije na električne procese i magnetske interakcije u željeznom fosfatnom staklu

doctoral thesis

• Title (english): Influence of crystallization on electrical prosses and magnetic interaction in iron phospate glass
• Author: Luka Pavić; MBZ: 312881
• Mentor: Andrea Moguš-Milanković (mentor)
• Committee member: Marina Cindrić (predsjednik povjerenstva)
• Committee member: Andrea Moguš-Milanković (član povjerenstva)
• Committee member: Željko Skoko (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Chemistry); Zagreb
• Defense date and country: 2014-11-28, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry
• Universal decimal classification (UDC): 54 - Chemistry. Crystallography. Mineralogy

Abstract

U okviru disertacije istraživan je utjecaj kristalizacije na električne procese i magnetske interakcije u staklu sastava 40Fe2O3-60P2O5(mol%). Kontroliranom kristalizacijom nastaju djelomično i potpuno kristalizirana stakla. Ovo staklo pokazuje elektronsku provodnost, kao rezultat preskoka elektrona s Fe2+ na Fe3- ione, i opisuje se modelom malog polarona, dok gledajući magnetska svojstva, pripada tzv. spinskom staklu. Istraživan je utjecaj temperaturno i vremenski kontrolirane kristalizacije na strukturne promjene, pojave različit ih kristalnih faza, njihove međusobne interakcije te električni transport i magnetska svojstva. Niz metoda je korišteno u istraživanju: DTA, XRPD, spektroskopije (Raman, Mössbauer i impedancija) te za magnetska mjerenja VSM. Ovisno o temperaturi i vremenu kristalizacije u staklenoj matrici nastaju kristalne faze Fe3(P2O7)2, Fe4(P2O7)3 i Fe(PO3), s različit im udjelima. Ukupna provodnost pada na početku kristalizacije te postiže minimum, a daljnjim povišenjem temperature kristalizacije provodnost raste s porastom kristalnosti. Detaljnom analizom impedancijskih spektara odvojeni su doprinosi pojedinih faza ukupnoj električnoj provodnosti. Magnetska mjerenja su pokazala dominantne ant iferomagnetske interakcije u svim uzorcima, a prisutne su također i slabe feromagnetske interakcije u kristaliziranim uzorcima.

Abstract (english)

In the thesis, the crystallizat ion effect on the electrical processes and the magnetic interactions in glass wit h composit ion 40Fe2O3-60P2O5(mol%) was investigated. Controlled crystallizat ion leads to partially and fully crystallized glasses. This glass exhibits the electronic conduct ion, as a result of electron hopping from Fe2+ to Fe3- ions, which is described by small polaron hopping model, whereas magnet ically belongs to the spin-glass. The influence of crystallizat ion temperature and t ime on structural changes, the appearance of crystalline phases, their interactions and influence on electrical transport and magnet ic properties have been invest igated. Various methods were used: DTA, XRPD, spectroscopy (Raman, Mössbauer and Impedance) together with magnetochemical measurements (VSM). Depending on crystallizat ion temperature and t ime, various phases occur in glass matrix such as: Fe3(P2 O7)2, Fe4(P2O7)3 and Fe(PO3). Total conduct ivit y decreases in the first stage of the crystallizat ion process and achieves its minimum. Wit h further increase of the crystallizat ion temperature, the electrical conduct ivit y rises as a result of an enhanced crystallinit y. Contribution of the each phase to the total conduct ivit y is determined. Magnetic measurements showed dominant antiferomagnet ic interactions in all samples but some weak ferromagnet ic interact ions were also present in crystallized samples.

• Keywords: električni procesi; kristalizacija; magnetske interakcije; struktura; željezno fosfatno staklo
• Keywords (english): electrical processes; crystallizat ion; magnet ic interact ions; structure; iron phosphate glass
• Language: croatian
• URN:NBN: urn:nbn:hr:217:038690
• 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: 188 str. ; 30 cm
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2018-08-30 11:43:45