Otrzymywanie i właściwosci dielektryczne ceramiki 0,7BiFeO3-0,3BaTiO3

In a present paper results of the process of synthesis and study of a perovskite-type solid solution of the chemical composition (1-x)BiFeO3-xBaTiO3 for x=0.3 are reported. Synthesis of 0.7BiFeO3-0.3BaTiO3 (BF-BT) ceramics was carried out according to the solid-phase reaction from the mixture of powders. Simultaneous thermal analysis (STA) and X-ray diffraction method were utilized to study the synthesis of BF-BT ceramics. On the basis of STA analysis the optimum conditions of the thermal treatment were found. BF-BT ceramics was studied in terms of its microstructure (SEM), chemical composition (EDS), crystalline structure (XRD), and dielectric properties (impedance spectroscopy) at room temperature. It was found that dense BF-BT ceramics with a cubic structure of Pm3m space group and desired stoichiometry (š3%) was fabricated under technological conditions differing in both sintering temperature (T=750°C-850°C) and soaking time (t=2h-40h). It was found that an increase in sintering temperature for ?T=100°C made it possible to decrease the soaking time 10 times. Impedance spectroscopy was utilized for characterizing dynamical dielectric properties of 0.7BF-0.3BT ceramics. The alternative representation of impedance data in a form of complex plot (Z" vs. Z') as well as simultaneous Bode plots (imaginary parts of impedance Z", admittance Y", electric modulus M" and tan versus frequency in a log-log scale) were used for preliminary visual analysis. Kramers-Kronig transform test was utilized for experimental data validation. To analyze the room temperature impedance spectroscopy data complex nonlinear least squares fitting method was used and the data were fitted to the corresponding equivalent circuit consisting of resistors and constant phase elements. Agreement between experimental and simulated data was established.W niniejszej pracy przedstawiono rezultaty badań poświęconych wytwarzaniu i charakterystyce właściwosci roztworu stałego o strukturze typu perowskitu i składzie chemicznym (1-x)BiFeO3–xBaTiO3 dla x=0,3. Proces syntezy ceramiki 0,7BiFeO3–0,3BaTiO3 (BF-BT) przeprowadzono w wyniku reakcji w fazie stałej z mieszaniny prostych tlenków. Przy pomocy analizy termicznej (STA) oraz rentgenowskiej analizy strukturalnej dokonano charakterystyki procesu syntezy ceramiki BF-BT. Przeprowadzono badania mikrostruktury ceramiki BF-BT za pomoca skaningowego mikroskopu elektronowego (SEM), określono stechiometrie składu chemicznego przy użyciu metody EDS, a strukture krystaliczna badano metoda dyfrakcji rentgenowskiej (RTG). Przeprowadzono badania właściwosci dielektyrcznych wytworzonej ceramiki metodą spektroskopii impedancyjnej. Wykorzystując metodę swobodnego spiekania dla trzech różnych warunków technologicznych (T=750-880 C, t=2-40h) otrzymano ceramike 0,7BF–0,3BT o dużej czystości i homogenicznosci składu (3%), wykazujaca strukture regularna Pm3m. Na podstawie przeprowadzonych badań stwierdzono, iż zwiększenie temperatury syntezy i spiekania o T=100 C, pozwoliło zmniejszyć czas wytrzymania ceramiki 10 razy. Badania przeprowadzone metoda spektroskopii impedancyjnej pozwoliły na scharakteryzowanie właściwosci dielektrycznych ceramiki 0,7BF–0,3BT. Dane impedancyjne przedstawiono w płaszczyznie zespolonej Z" od Z' oraz w postaci zależności częstotliwościowych urojonych składowych impedancji Z"(v), modułu elektrycznego M"0(v), admitancji Y"(v) i strat dielektrycznych tg(v). Spójność danych pomiarowych sprawdzono przy pomocy metodyki Kramersa-Kroniga, która potwierdziła poprawność danych eksperymentalnych

The Effect of Ho Doping Contents on the Structural, Microstructure and Dielectric Properties of Bi5Ti3FeO15 Aurivillius Ceramics

Aurivillius Bi5-xHoxTi3FeO15 (BHTFO) multiferroic ceramics with different holmium doping contents were synthesized by conventional solid state reaction. The effect of holmium doping on the microstructure, structural and dielectric behaviors of BHTFO ceramics were investigated in details. Microstructure and crystalline structure studies of ceramics were carried out at room temperature while dielectric properties were investigated in a wide range of temperature (T = 25ºC-550ºC) and frequency (20Hz-1MHz)

Study of Phase Transition in Bi3TiNbO9-BaBi2Nb2O9 Ceramics

The subject of the paper is lead free bismuth layer structure oxides (1-x)Bi3TiNbO9-xBaBi2Nb2O9 (x=0; 1; 2; 3 mol). The influence of Bi3TiNbO9/BaBi2Nb2O9 ratio on dielectric and structural properties was studied in a wide range of temperatures. Change in the ratio causes a decrease in the maximum value of dielectric permittivity and shifts the temperature of ε’max to low values, leading to linear decreasing of average grain size and linear increasing of ceramics density. These results indicate an augment of the packing degree and the participation of pores are significantly decreased with the increase of BaBi2Nb2O9 compound intake. Moreover, for 0.7Bi3TiNbO9-0.3BaBi2Nb2O9 ceramics the dielectric phase transition is broadened and the properties characteristic for the ferroelectric relaxor appear

Impedance spectroscopy of vanadium modified BaBi2Nb2O9 ceramics

In recent years a wide range of Aurivillius layered materials have been introduced. These novel materials are produced in many various forms such as fibers, thin films as well as bulk by using a number of processing routes. As advanced materials they are they have many interesting properties which include a number of useful electrical properties related to separated grain and grain boundary conductivity, impedance, activation energies, etc. In this paper these properties are described and discussed in detail. The electrical properties of the vanadium doped BaBi2Nb2O9 ceramic was measured over a wide range of temperatures by impedance spectroscopy (IS). The separated grain activation energy, calculated from Arrhenius characteristics at temperatures between room temperature and 600 °C, was 1 eV for 0 at.% of vanadium dopant and 1.2 eV for 10 at.%, whereas the activation energies in the grain boundary region were 0.97 and 1.15 eV, respectively. The obtained results suggest the significant role of vanadium dopant, causing ordering the crystalline structure