L. Szymczak

Dielectric and pyroelectric properties of Nb-doped Pb(Zr0.92Ti0.08)O3 ceramics

Abstract Dielectric and pyroelectric characteristics and changes of electric conductivity were investigated for Nb 2 O 5 -doped Pb(Zr 0.92 Ti 0.08 )O 3 ceramics. The influence of this dopant on the ceramics microstructure was also studied. Correlation between the investigated electric characteristics and grain structure was confirmed. Some progress in understanding the influence of Nb-dopant was reached in this way.

Influence of sintering conditions on relaxor properties of BaBi2Nb2O9 ceramics

The main purpose of present studies is to learn the effect of sintering temperature on BaBi2Nb2O9 (BBN) ceramics properties. Grain structure analysis performed by the scanning electron microscope (SEM) exhibits differences in grain structure of the ceramics sintered at various temperatures for a constant time. Namely, the grain sizes increase with the increase of the sintering temperature. This fact is connected with changes in dielectric properties. The maximum of the real part of permittivity ( ) and corresponding temperature (T m) shifts to higher values. The properties characteristic for the ferroelectric relaxors also yield to change. The ceramics sintered in higher temperature revealed lower frequency dispersion of and T m. It should also be noticed that the freezing temperature and the Burns temperature have changed. These results indicate that the behaviour of the relaxor ferroelectrics is weakened by the increase in the grain size.

Dielectric, Pyroelectric and Thermally Stimulated Depolarization Current Investigations on (Ba, Sr)TiO3 Ceramics with Bi2O3 Additive

The Ba1−x Sr x TiO3 materials have received increased attention as one of the most important materials for electroceramic components, such as high dielectric ceramic capacitors, tunable phase shifters and PTCR. In this paper the effect of 0.5; 1; 1.5; and 2 mole% of Bi2O3 addition on microstructure, structure, dielectric properties (i.e., dielectric constant ϵ′, and dielectric loss factor tan δ), as well as pyroelectric and thermally stimulated depolarization currents (TSDC) of (Ba0.8Sr0.2)TiO3 ceramics have been investigated. The distinct correlation between Bi2O3 content, wide maxima in TSDC, anomalies in ϵ′ (T) and tan δ (T) characteristics occurring within the range of the paraelectric phase was confirmed. Changes of electric conductivity and Seebecks coefficient, caused by Bi2O3-additives, were also studied.

Relaxor properties of Nb-modified (Ba0.8Sr0.2)TiO3 ceramics

Nb-doped (Ba0.8Sr0.2)TiO3 ceramics were prepared using conventional mixed-oxide processing technique. Permittivity and loss factor were investigated as a function of temperature for various frequencies of the measuring field. The obtained results confirmed the relaxor ferroelectric behaviour of the studied ceramics, i.e. a strong frequency dispersion of the permittivity maximum and a visible shift of its temperature with frequency. Analysis of real part of permittivity allowed us to determine the value of the freezing temperature characterising the relaxor ferroelectrics. The physical processes, responsible for the relaxor behaviour of the studied ceramics are discussed.

Effect of Sb doping on phase transition and relaxor behaviour of (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 ceramics

The effect of antimony dopant on phase transition, dielectric response and relaxor behaviour of (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 ceramics was studied. Ceramic samples, with various Sb concentration from the range 1 to 4 at.%, were prepared by a conventional mixed oxide method. The crystal structure of the investigated ceramics was determined by an X-ray diffraction at room temperature that allowed to determine the unit cell parameters. Dielectric relaxation typical for ferroelectric relaxors was observed in the vicinity of diffuse ferroelectric–paraelectric phase transition. All parameters describing the relaxor behaviour determined from the Vogel–Fulcher relationship depend on the concentration of Sb dopant. The strong influence of antimony on grain structure and on remanent polarisation was confirmed as well.