Ewa Nogas-Ćwikiel

Dielectric and pyroelectric properties of the Ba0.3Na0.7Ti0.3Nb0.7O3 ceramics obtained by sol-gel method

The solid solution of barium titanate (BaTiO3) and sodium niobate (NaNbO3) -- Ba1−x Na x Ti1−x Nb x O3 (BNTN) is a new lead-free material. BNTN ceramics obtained by the conventional ceramic method possess the classical ferroelectric behaviour when 0<x<0.075 and 0.55<x<1 and relaxor behaviour when 0.075 ≤ x ≤ 0.55 1. In this work we present the results of the investigations of the dielectric and pyroelectric properties of the Ba1−x Na x Ti1−x Nb x O3 ceramics for x = 0.7 obtained, for the first time, from sol-gel derived powders. The temperature dependences of the dielectric permittivity ε′(T) within the frequency range 65 Hz–1 MHz and the pyroelectric current were investigated. The temperature range of the measurements was 90–470 K.

Ceramics With Tetragonal Tungsten Bronze Type Structure For Textured Ceramics-Polymer Composites

Textured Sr0.7Ba0.3Nb2O6-PVDF (SBN70-PVDF) composites were fabricated. Powders of strontium barium niobate Sr0.7Ba0.3Nb2O6 (SBN70) were prepared by sol-gel method. The composite surface images were obtained by AFM tapping mode (NT-MDT Solver P47). The pyroelectric properties have been studied. The obtained composite is expected to be promising material for pyroelectric detectors.

Technology and Properties of (1-x)PZT-(x)PFW Ceramics with 0.25<x<0.55

We present the results of obtaining and investigating ceramic samples of solid solution (1-x)(PbZr0.53Ti0.47O3)-x (PbFe2/3W1/3O3) [i.e. (1-x)PZT-xPFW] with x = 0.25, 0.35, 0.45 and 0.55 obtained from oxides using conventional ceramic technology. In this paper we present the results of investigations of XRD and main dielectric properties. For x = 0.25 and x = 0.35 we investigated also P-E hysteresis loops at room temperature.

Magnetic properties and phase diagram of (1-x)PZT-(x)PFW ceramics with 0.25<x<0.55

Solid solution (1−x)(PbZr0.53Ti0.47O3)−x(PbFe2/3W1/3O3) [i.e. (1-x)PZT-xPFW] belongs to materials called multiferroics. Such materials are interesting due to their potential practical applications, and also because of the possibility to investigate the basics of physical phenomena occurring in them. We obtained ceramic samples of PZT-PFW from oxides using classic ceramic technology and earlier we studied their basic dielectric properties. In this work we describe the results of investigations magnetic properties which have been made using the QD MPMS-XL-7 SQUID magnetometer. Basing on these measurements of electric and magnetic properties and on the literature data we have constructed extended phase diagram of this solid solution.

Dielectric response of PVC polymer loaded with Ba0.3Na0.7Ti0.3Nb0.7O3 ceramic powder

Dielectric response of poly(vinyl chloride), (PVC), loaded with different amount of Ba0.3Na0.7Ti0.3Nb0.7O3 (BNTN) ceramic powders was investigated in frequency range 100 Hz–1 MHz and temperature range 100–450 K. Ceramic solid solution of barium titanate and sodium niobate with composition Ba0.3Na0.7Ti0.3Nb0.7O3 was obtained from BaCO3, TiO2, Na2CO3 and Nb2O5 by conventional method. Powders were prepared by grinding of ceramics. The obtained ceramics, used to produce BNTN–PVC composites, are characterized by the relaxor behaviour with a broad peak of dielectric permittivity ε′ at T m ≈ 230 K. The microstructure of the powders was observed and the grain size was estimated using scanning electron microscope Hitachi S-4700. The EDS analysis confirms the qualitative and quantitative chemical composition of powders and ceramics. The BNTN–PVC composite samples of 0-3 connectivity were prepared from ceramic and polymer powders by hot-pressing method. The dielectric response of the composites displays features originated from the PVC polymer modified by those of BNTN ceramics. The relaxation time of the α-process of PVC obeys the Vogel–Fulcher law and decreases with increasing volume fraction of the ceramics.

Dielectric behaviour and pyroelectricity in SBN70-PVC composites

Dielectric relaxation of the composites of 0–3 connectivity, made from Sr0.7Ba0.3Nb2O6 (SBN70) ceramic powder and poly(vinyl chloride) (PVC), with the volume fraction of ceramics Φ up to 0.2 was investigated in frequency range 100 Hz–1 MHz and temperature range 100–450 K. The SBN70-PVC composites samples were prepared from ceramic and polymer powders by hot-pressing method. The SBN70 ceramics was prepared by a sol-gel route. The microstructure of the powders was observed and the grain size was estimated using Hitachi S-4700 scanning electron microscope (SEM). The investigations of the pyroelectric response were performed using a modified, computer controlled Chynoweth method at room temperature a few months after poling. The SBN70 ceramics modifies the dielectric properties of the PVC polymer: (i) it increases the value of dielectric permittivity of the composites in the whole temperature range, (ii) the composite displays a maximum of the permittivity coming from dielectric anomaly of the ceramics. The addition of the ceramics weakly influences the dynamics of the polymer dielectric relaxation α described by Vogel--Fulcher model. The value of the pyroelectric coefficient p of poled composites increases with volume fraction of SBN70 ceramics. The p for composites with the Φ = 0.2 at modulation frequency of 1 Hz is about 100 µC m−2 K−1.

Thermal, Raman, dielectric and ferroelectric properties of 0.975BaTiO3-0.025Pb(Zn1/3Nb2/3)O3 ceramic

ABSTRACT A new low-lead content 0.975BaTiO3-0.025PbZn1/3Nb2/3O3 (0.975BT-0.025PZN) ceramic with a high relative density and good mechanical quality was fabricated by the SPS method. X-ray diffraction measurements showed that the obtained specimen possesses a pure perovskite structure. The composition undergoes a sequence of phase transitions as pure BT. Dielectric studies revealed that the dielectric permittivity decreases at its maximum and the phase transitions shift after PZN-doping of BT. In addition, the dielectric dispersion and polarization increases and decreases, respectively. Possible reasons for the observed properties change are discussed. The results show that the investigated ceramic is a promising low-lead material for electronic applications.

Thermal, dielectric and ferroelectric properties of 0.925BaTiO3–0.075Pb(Zn1/3Nb2/3)O3 ceramic

New low-lead content 0.925BaTiO3–0.075PbZn1/3Nb2/3O3 (0.925BT–0.075PZN) ceramic was fabricated by the spark-plasma-sintering method. X-ray diffraction measurements showed that the obtained specimen possesses a pure perovskite structure. The microstructure investigation indicated a dense ceramic structure with 95% relative density determined by the Archimedes method. Composition undergoes a sequence of phase transitions as pure barium titanate (BT). Dielectric study revealed that the electric permittivity decreases at its maximum and the phase transition shifts to a higher temperature after lead zinc niobate doping of BT. Besides, the dielectric dispersion and polarization increases and decreases, respectively. Obtained results were discussed in term of the difference between ionic size and its mass and local elastic and electric fields. The results show that investigated ceramic is one of the promising low-lead materials for electronic applications.

Influence of SBN70 concentration in PVDF on dielectric and pyroelectric properties of nanocomposites

Strontium barium niobate Sr0.7Ba0.3Nb2O6 (SBN70) ceramic nanopowder was dispersed in a poly(vinylidene fluoride) (PVDF) matrix providing a composite with 0–3 connectivity. The SBN70-PVDF composites samples were obtained from ceramic and polymer powders by hot-pressing method. The SBN70 ceramic was prepared by a sol-gel method. The composite surface images were obtained by AFM tapping mode (NT-NDT Solver P47). The dielectric response of the composites was studied in the frequency range 100 Hz – 1 MHz and the temperature range 100 – 430 K. The dielectric properties of the composites display features originated from the PVDF polymer modified by those of SBN70 ceramics. The resulting pyroelectric currents were measured using a Keithley 6517 A electrometer and were used to calculate the pyroelectric coefficient p. The p of poled composites increases from ~24 μC/m2K in pure PVDF to ~40 μC/m2K in the composites of Φ = 0.2 at room temperature.