Papers by Author: Vladimir V. Srdic

Abstract: The evolution of the magnetism as a function of the particle size is reported here for the ZnFe2O4 nanoparticles. A combination of neutron powder diffraction down to 1.5 K and magnetization measurements suggest that nanoparticles of sizes greater than about 100 nm exhibit bulk like behavior. The size dependence on magnetism can be explained by the rearrangement of the cations on the interstitial sites of the spinel cell.

Abstract: Cerium- and lanthanum- substituted bismuth titanate (Bi4-xAxTi3O12; where A=La or Ce, and x=0, 0.5 and 1) ceramics were prepared from nanopowders synthesized by coprecipitation method. The as-synthesized powders were calcined, uniaxially pressed and finally sintered at 1050°C. It was shown that sintering behaviour, phase composition and grain morphology of the obtained ceramics were influenced by the presence of lanthanum and especially cerium ions in the titanate structure. Mechanical properties (hardness and fracture toughness) were measured at room temperature on polished sample surfaces using a Vickers microhardness tester. The hardness values for of bismuth titanate based ceramics were in the range for some other important perovskite titanate, whereas their fracture toughness was somewhat higher.

Abstract: Yttrium- and indium-doped zinc-ferrite nanoparticles were prepared by a coprecipitation method. The influence of doping level on the structure and the conductivity of the samples obtained was investigated. It was found that Y-doped zinc-ferrite nanoparticles, with a single spinel phase and a size of a few nanometers, are formed in the whole range of yttrium concentration. However, In-doped zinc-ferrite nanoparticles were formed for all investigated indium cooncentrations, but only the samples InxZn1-xFe2O4 with x.≤ 0.15 are single-phase (for x ≥ 0.20 a second phase - cubic In(OH)3, is formed). The decrease and increase of the electrical conductivity with yttrium and indium doping respectively are explained by taking into consideration the different role of these ions in the spinel structure and the electron hopping mechanism.