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Publikācija: Electrical and Structural Properties of Nanostructured Stoichiometric and Non-Stoichiometric Ni-Zn Ferrites

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Nosaukums oriģinālvalodā Electrical and Structural Properties of Nanostructured Stoichiometric and Non-Stoichiometric Ni-Zn Ferrites
Pētniecības nozare 2. Inženierzinātnes un tehnoloģijas
Pētniecības apakšnozare 2.5. Materiālzinātne
Autori Andris Šutka
Gundars Mežinskis
Laimons Timma
Inta Vītiņa
Artūrs Plūdons
Atslēgas vārdi Ni-Zn ferrite, sol-gel auto combustion method, electric and dielectric properties
Anotācija The spinel Ni-Zn ferrites for a long time has been used in various electromagnetic applications and electronic devices, such as transformer cores, microwave absorbing materials and devices, inductors etc. Currently there is interest to make nanostructured Ni-Zn ferrite in order to increase resistivity and reduce energy loses, as well as reduce structural and chemical heterogeneity [1]. It is important in many applications to control the resistivity of nanostructured ferrites, but information about electric, dielectric and structure properties of Ni-Zn ferrite is still limited. Also little research has been conducted on nanostrucutred non-stoichiometric Ni-Zn ferrite and ability to control and improve its structural and electrical properties. The spinel ferrite structure with general formula AB2O4 contains 8 tetrahedral coordinated sites (A) and 16 octahedral coordinated sites (B) for metal cation occupancy [2]. Ni-Zn ferrite has mixed spinel structure – both divalent and trivalent ions are located among tetrahedral and octahedral sublattice sites [2]. Normally in Ni-Zn ferrite Zn2+ shows a strong preference for occupying the tetrahedral sites while Ni2+ prefers incorporation at the octahedral sites. Conduction in the spinel ferrites occurs through electron or hole transfer in the octahedral site between one element different valence metal ions. It is known that by changing iron content in Ni-Zn ferrite we can observe p- or n-type conductivity. For example, in iron excess ferrites Fe3+ reduces to Fe2+, thus electron transfer is possible showing n-type conductivity. Type of conductivity also can change with Ni/Zn ion relation. By increasing Ni2+ ion content Ni-Zn ferrite shows to p-type conductivity, but by increasing Zn2+ content n-type conductivity. This can be explained with Ni2+ oxidation to Ni3+ in high nickel content Ni-Zn ferrites and with Zn2+ volatilization and Fe2+ formation at high zinc content Ni-Zn ferrites. For nanosized particles lower sintering temperatures are necessary providing to prevent grain growth and increase volume of grain boundaries, as well as reduce concentration of localized charge carriers, thus extraordinary electric and dielectric properties could be observed. The aim of the present study was to investigate the structural, electrical and dielectric properties of stoichiometric and iron excess ferrites prepared by sol-gel auto-combustion method. Results show that nanostructured ferrites have strongly different electric properties in comparison with microstructured stoichiometric and iron excess Ni-Zn ferrites.
Atsauce Šutka, A., Mežinskis, G., Timma, L., Vītiņa, I., Plūdons, A. Electrical and Structural Properties of Nanostructured Stoichiometric and Non-Stoichiometric Ni-Zn Ferrites. No: 5th Baltic Conference on Silicate Materials (BaltSilica 2011): Book of Abstracts, Latvija, Rīga, 23.-25. maijs, 2011. Riga: RTU Publishing House, 2011, 34.-35.lpp. ISSN 2243-6057.
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