0000000000014712
AUTHOR
G. Stopa
showing 8 related works from this author
Structural and Dielectric Properties of Na0.99Li0.01NbO3Ceramics
2006
Na0.99Li 0,01 NbO3 ceramics were prepared by solid-state reaction method. The samples were characterized by X-ray diffraction, microstructure and dielectric permittivity measurements. The X-ray diffraction analysis showed that samples have a single phase of perovskite structure with orthorhombic symmetry. Microstructure investigations revealed crystalline structures in grains. It was found that dielectric properties of Na99Li0.01NbO3 ceramic are sensitive to the applied axial pressure. This includes the shift of phase transformation, diffuseness of the ϵ (T) profile and reduction of the thermal hysteresis. These effects can be caused by change in domain structure and anisotropy of crystalli…
LEAD-FREE (Na0.5Bi0.5)1-xBaxTiO3 SINGLE CRYSTALS (0 ≤ x ≤ 0.05) AND THEIR DIELECTRIC AND PYROELECTRIC PROPERTIES
2009
ABSTRACT Lead-free single crystals of Na0.5Bi0.5TiO3-BaTiO3 (NBT-BT) system were prepared by Czochralski method and their dielectric and pyroelectric properties have been studied. The results were compared with these for pure NBT. The obtained samples show pure perovskite structure with rhombohedral symmetry at room temperature. Low frequency (100 Hz–100 kHz) investigations reveal the diffuse phase transitions. The obtained results are discussed in terms of local electric and strain fields caused by different ionic radius of (Na, Bi) and Ba ions. The NBT-BT system is expected to be a new promising candidate for lead-free electronic crystals.
Uniaxial Pressure Effect on Electric Properties of PSN and 0.95PSN-0.05PLuN Ceramics
2006
The dielectric, pyroelectric and hysteresis loops measurements of PSN and 0.95PSN-0.05PLuN ceramics stress-free and under the stress (0–1.5 kbar) have been carried out. It was shown that axial pressure seems to change the partially ordered state to a disordered one, shifts the phase transformation and decreases the thermal hysteresis of the dielectric permittivity and the field-polarization hysteresis. These effects can be connected with change in domain structure, inter-ionic distances and defect density under the action of uniaxial pressure. The thermodynamic parameters of the phase transition were also determined.
Electrical Transport Properties of Lead−Free (Na0.5Bi0.5)1-xBaxZr0.04Ti0.96O3Ceramics (x = 0.06, 0.085, 0.1)
2011
Lead-free ceramics (Na0.5Bi0.5)1-xBaxZr0.04Ti0.96O3 were prepared by solid phase hot pressing sintering process. Density values of obtained samples are higher than 95% of the theoretical ones. Samples with x = 0.06, 0.085 and 0.1 were investigated in the present work. For these samples both ac and dc electric conductivity were studied. A low frequency (100 Hz-100 kHz) ac conductivity obeys the power law, characteristic for disordered materials. The dc conductivity has a thermally activated character. A barrier hopping model is found to explain the mechanism of charge transport in these materials. The (Na0.5Bi0.5)1-xBaxZr0.04Ti0.96O3 system is expected to be a new and promising candidate for…
DIELECTRIC PROPERTIES OF LEAD-FREE [(1-x)(Na0.5Bi0.5)-xBa]Zr1−yTiyO3CERAMICS (x = 0.01, 0.06, 0.085, 0.09, 0.1 AND y = 0.96, 0.97)
2008
ABSTRACT Lead-free ceramics based on (Na0.5Bi0.5TiO3, NBT)-(Ba(Ti, Zr)O3, BTZ) were prepared by solid phase synthesis and hot pressing sintering process and their dielectric properties have been studied. The obtained results were compared with these for pure NBT. The obtained samples show pure perovskite structure. Low frequency (100 Hz-100 kHz) investigations reveal the diffuse phase transitions and relaxorlike behaviour. The obtained results are discussed in terms of inhomogeneity of ions distribution, their ferro- and antiferroactivity and internal stresses. The NBT-BTZ system is expected to be a new promising candidate for lead-free electronic ceramics.
Electrical Transport in Lead-Free [(1−x)(Na0.5Bi0.5)-xBa]Zr1 - yTiyO3Ceramics (x = 0, 0.06, and y = 0, 0.96)
2009
Lead-free ceramics based on (Na 0.5 Bi 0.5 TiO 3 , NBT)-(Ba(Ti,Zr)O 3 , BTZ) were prepared by solid phase hot pressing sintering process and their ac (σ ac ) and dc (σ dc ) conductivity have been studied (303–753 K). Low frequency (100 Hz–100 kHz) ac conductivity obeys power law σ ac ∼ ω s characteristic for disordered materials. The frequency exponent s is a decreasing function of temperature and tends to zero at high temperatures. Dc conductivity has thermally activated character and possesses four linear parts with four different activation energies and some discontinous changes. However, σ ac (T) possesses two linear parts with two different activation energies and more discontinuous ch…
The structural and dielectric properties of the Na0.96Li0.04NbO3ceramics
2007
Ceramic samples Na0.96Li0.04NbO3 were obtained using ceramic technology. The phase and structural analysis, the microstructure, EDS and EPMA, dielectric and hysteresis loops measurements have been performed. The dielectric and hysteresis loops measurements of Na0.96Li0.04NbO3 have been carried out. The dielectric measurements were performed both without and under axial pressure up to 120 MPa. It was shown that Na0.96Li0.04NbO3 ceramics have orthorhombic symmetry at room temperature and undergo a first order phase transition at a temperature of about 570 K. The axial pressure shifts the phase transition temperature and decreases the hysteresis in field-polarisation and field-strain dependenc…
Influence of Unaxial Pressure on Electric Properties of (1-x)PSN-xPLuN Solid Solutions (0.75 ≤ x < 1)
2007
(1-x)PSN-xPLuN ceramics with single phase perovskite structure and rhombohedral symmetry at room temperature were prepared by solid-state reaction method. The influence of unaxial pressure (0–1500 bars) on dielectric properties of these compounds were studied. It is found that these materials are sensitive to external stress. This includes the shift of phase transitions, diffuseness of dielectric permittivity characteristics and the decrease of the thermal hysteresis of the permittivity and field-polarization hysteresis. These changes of properties could be connected with the change in domain structure, the elastic change of distances between ions and the change in defects density.