In the present paper results of the dielectric investigation of barium titanate (BaTiO3) doped with different concentrations of lanthanum are presented. Ceramic samples were prepared by the Pechini process. With increased doping the grain size of ceramics decreases from 2.5 ?m in pure samples down to 0.2 ?m in 0.5 mol% La - doped BaTiO3. Ceramics showed maximally enhanced dielectric permittivity around low-, room and high temperature phase transitions, which are the phase transitions of the pure BaTiO3. The Curie temperature, TC, is lowered by 30 K with increase of doping concentration to 0.5 mol% La. Dielectric spectra revealed three parts: low frequency part which is caused by conductivity process, middle frequency relaxational process part and high frequency relaxational/polar modes contribution.
Ni-Zn ferrites, with the general formula Ni 1-x Zn x Fe 2 O 4 (x = 0.0, 0.3, 0.5, 0.7, 1.0), CoFe 2 O 4 , BaTiO 3 and PbZr 0.52 Ti 0.48 O 3 powders were synthesized by auto-combustion method. The composites were prepared by mixing the appropriate amounts of individual phases, pressing and conventional sintering. X-ray analysis, for individual phase and composites, indicated the formation of crystallized structure of NiZnFe 2 O 4 , BaTiO 3 and PbZr 0.52 Ti 0.48 O 3 without the presence of secondary phases or any impurities. SEM analyses indicated a formation of uniform grain distribution for ferromagnetic and ferroelectric phases and formation of two types of grains, polygonal and rounded, respectively. Magneto-dielectric effect was exhibited in all samples because of the applied stress occurring due to the piezomagnetic effect and the magnetic field induced the variation of the dielectric constant. For all samples the dielectric constant was higher in applied magnetic field. At the low frequency, the dispersion of dielectric losses appeared, while at the higher frequency the value of tan δ become constant (Maxwell-Wagner relaxation). Investigation of J-E relation between leakage and electric field revealed that both nickel zinc ferrite and composites have three different regions of conduction: region with ohmic conduction mechanism, region with the trap-controlled space charge limited current mechanism and region with space charge limited current mechanism.
Composites based on barium titanate and nickel zinc ferrite doped with cooper and samarium were prepared by a mixing method. The formation of barium titanate tetragonal crystal structure and nickel zinc ferrite cubic spinel structure was identified. Polygonal grains were formed in all three types of ceramics. Due to the very high conductivity of ferrite phase in the materials the ferroelectric hysteresis loops were roundish and not typical for classical ferroelectric material. The break down field was found to be similar for all compositions. Leakage current measurements have shown the existence of different types of conductivity mechanisms in each material. The impedance analysis suggested a bit stronger impact of grain boundaries on total conductivity of the composites and the mechanism of polaronic conduction of two types. The magnetization of the composites is lower than for the pure ferrite phase and corresponds to the weight fraction of the ferrite phase. The soft magnetic nature of these composites might be very useful for development of multifunctional devices which will be able to switch the magnetization with small external magnetic field. Humidity sensing properties of the prepared ceramics were also investigated.
Roles of various organic crystals (OC), notably those containing nitrogen, on the preparation and properties of source materials for electroceramics are featured from the author's own experimental studies. When OC are intimately mixed with metal salts like carbonates, their decomposition is accelerated, liberating the diffusing species at temperatures lower than usual. Mixing of OC with metal oxides under mechanical stressing results in anion exchange and eases diffusion of guest species. Case studies on 3 categories, i.e. i) substitution of oxygen in titania with nitrogen and introduction of oxygen vacancies during co-grinding titania with urea, glycine and/or polytetra fluoroethylene; ii) increase in the rate of reaction of barium titanate formation via a solid state route by OCs with detailed process analysis with glycine as an example of OC, and iii) phase pure solid state synthesis of Li4Ti5O12 by mechanically activating the intermediate, Li2TiO3 with 3 amino acids as OCs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.