Synthesis of 0.7BiFeO3-0.3BaTiO3 ceramics : thermal, structural and AC impedance studies

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 ( 3%) 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 (Z00 vs. Z0) as well as simultaneous Bode plots (imaginary parts of impedance Z00, admittance Y00, electric modulus M00 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

Synteza, mikrostruktura i struktura krystaliczna ceramicznego tytanianu baru domieszkowanego lantanem

In the present study BaTiO3 and Ba1xLaxTiO3 (0.1-0.4mol.% La) ceramic powders were synthesized by the conventional mixed oxide method (MOM). The characterization of the ceramic powders was carried out using a simultaneous thermal analysis (STA), with a combined DTA/TG/DTG system (Netzsch STA409). The results of thermal analysis allowed to determine the optimal temperature of synthesis. Microstructure was investigated by scanning electron microscopy (SEM), crystalline structure was studied by X-ray diffraction method (XRD). The EDS investigations showed that samples exhibited conservation of stoichiometry according to the chemical composition formula. The X-ray diffraction analysis confirmed formation of the desired crystalline structure both pure and La3+-doped BaTiO3 ceramics exhibiting a perovskite-type structure ABO3 with tetragonal symmetry P4 mm

Correction: Wodecka-Dus, B. et al., Chemical and Physical Properties of the BLT4 Ultra Capacitor - A Suitable Material for Ultracapacitors Materials 2020, 13, 659

Correction to article: Wodecka-Dus, B. et al., Chemical and Physical Properties of the BLT4 Ultra Capacitor - A Suitable Material for Ultracapacitors Materials 2020, 13, 65

Chemical and physical properties of the BLT4 ultra capacitor - a suitable material for ultracapacitors

This paper describes the properties of a lead-free ceramic material based on barium titanate, designed for the construction of ultracapacitors and sensors used in mechatronic systems. The admixture of lanthanum (La3+) served as a modifier. The ceramic powders were obtained by the solid phase reaction method (conventional method-mixed oxides method-MOM). Technological conditions of the synthesis process were determined on the basis of thermal analysis. The obtained samples are characterized, at room temperature (Tr < TC), by a single-phase tetragonal structure and a P4mm space group. Properly developed large grains (d = 5 m) contributed to the increase in electric permittivity, the maximum value of which is at the level of "m 112,000, as well as to a strong decrease in specific resistance in the ferroelectric phase, whereas above the Curie temperature, by creating a potential barrier at their boundaries, there was a a rapid increase in resistivity. The temperature coe cient of resistance of the obtained posistor is 10.53%/K. The electrical properties of the obtained ceramics were examined using impedance spectroscopy. In order to analyze the obtained results, a method of comparing the behavior of the real object and its replacement system in a specific frequency region was used, whereas the Kramer—Kroning (K–K) test was used to determine the consistency of the measured data. The proper selection of the stoichiometry and synthesis conditions resulted in the creation of an appropriate concentration of donor levels and oxygen gaps, which in turn resulted in a significant increase in the value of electrical permittivity, with small values of the angle of dielectric loss tangent. This fact predisposes the discussed material for certain applications (in the construction of ultracapacitors, among others)

Wpływ warunków otrzymywania na fizyczne właściwości ceramiki PLZT:Nd3+

The aim of this work was to study the effect of fabrication conditions and neodymium co-doping on the physical properties of (Pb0:98La0:02)(Zr0:65Ti0:35)0:98O3, known as PLZT:Nd3+ ceramics. All ceramic powders of these materials were synthesized by the conventional mixed oxide method, from the high purity raw materials (>99.9%). The bulk ceramic samples were sintered by the pressure less sintering and the hot-uniaxial pressing techniques. The study gives a detailed account of the relationships between doping and preparing conditions on the dielectric and optical properties of obtained ceramic materials. Optimal conditions of PLZT:Nd3+ preparation as well as Nd3+ activator concentration were determined in relation to the potential opto-electronic applications

Hot pressed K0.5Na0.5nbo3 material for piezoelectric transformer for energy harvesting

An optimized method of vibration Energy Harvesting is based on a step-down transformer that regulates the power flow from the piezoelectric element to the desired electronic load. Taking into account parameters of the whole system, the “optimal” voltage gain the piezoelectric transformer can be determined where the harvested power is maximized for the actual level of mechanical excitation. Consequently the piezoelectric transformers can be used to boost up the conversion of mechanical strain into electrical power with considerable potential in Energy Harvesting applications. Nowadays however, the most important factor is usage of lead free material for its construction. Additional desired parameters of such ceramics include high value of piezoelectric coefficients, low dielectric losses and reasonable power density. This work for first time proposes a lead free K0.5Na0.5NbO3 (KNN) material implementation for stack type of piezoelectric transformer that is designed for load efficiency optimization of vibration energy harvester

Fabrication and dielectric properties of modified calcium (Pb0.75Ba0.25)(Zr0.7Ti0.3)O3 ceramics

The aim of the present work is to report investigations concerning the influence of homovalent modificators on relaxor properties of PBZT 25/70/30 ceramics. The selection of the proper homovalent additive was very important. Literature reports as well as data taken from the periodic table indicated, that calcium ions substitute themselves for lead ions with high likelihood of occurrence. The investigations showed that the substitution significantly changed the microstructure of ceramics – with grains of calcium modified ceramics decreasing and density increasing. The XRD measurements indicate that the pure PBZT ceramics as well as calcium dopant were characterised by tetragonal structure with space group I4/mmm. Addition of calcium leads to a slight decrease in the lattice constant and crystal structure. The calcium modification also changes the dielectric properties. The temperature characteristic of the dielectric constant achieved a broadened maximum at temperature Tm, which decreases with increasing Ca content. The properties typical for ferroelectric relaxors weaken with increasing calcium dopant

Influence of Sr2+ dopant on microstructure and electric properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) ceramics

The discovery of (BaxCa1-x)(ZryTi1-x)O3 lead-free ceramics drawn a lot of attention to those novel materials because of their excellent piezoelectric properties. However, quite a little attention has been paid to other features of the material. This article reports a wide range of research, including composition, structure and microstructure, dielectric response and impedance spectroscopy in order to systematize and expand knowledge about this peculiar ceramics and strontium doping effect on its properties. In order to test that influence a series of samples with various strontium concentration, precisely the admixtures of 0.02, 0.04 and 0.06 mol% were prepared, as well as basic ceramics to compare obtained results.[1] J. Hao, W. Bai, W. Li, J. Zhai, Correlation Between the Microstructure and Electrical Properties in High-Performance (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Lead-Free Piezoelectric Ceramics, J. Am. Ceram. Soc. 95, 1998-2006 (2012) doi:10.1111/j.1551--2916.2012.05146.x. [2] J. Suchanicz, Bezołowiowe tytaniany ferroelektryczne, Uniwersytet Pedagogiczny im. Komisji Edukacji Narodowej (Kraków), Wydawnictwo Naukowe, Wydawnictwo Naukowe Uniwersytetu Pedagogicznego, Kraków, 2016. [3] W. Liu, X. Ren, Large Piezoelectric Effect in Pb-Free Ceramics, Phys. Rev. Lett. 103 (2009). doi:10.1103/PhysRevLett.103.257602. [4] P. Parjansri, U. Intatha, S. Eitssayeam, Dielectric, ferroelectric and piezoelectric properties of Nb 5+ doped BCZT ceramics, Mater. Res. Bull.65, 61-67 (2015). doi:10.1016/j.materresbull.2015.01.040. [5] C. Han, J. Wu, C. Pu, S. Qiao, B. Wu, J. Zhu, D. Xiao, High piezoelectric coefficient of Pr2O3-doped Ba 0.85Ca0.15Ti0.9Zr0.1O3 ceramics, Ceram. Int. 38, 6359-6363 (2012). doi:10.1016/j.ceramint.2012.05.008. [6] Y. Cui, C. Yuan, X. Liu, X. Zhao, X. Shan, Lead-free (Ba0.85-Ca0.15)(Ti0.9Zr0.1)O3-Y2O3 ceramics with large piezoelectric coefficient obtained by low-temperature sintering, J. Mater. Sci. Mater. Electron. 24, 654-657 (2012). doi:10.1007/s10854-012--0785-7. [7] D. Zhang, Y. Zhang, S. Yang, Microstructure and electrical properties of tantalum doped (Ba0.85Ca0.15)(Ti 0.9Zr0.1)O3 ceramics, J. Mater. Sci. Mater. Electron. 26, 909-915 (2014). doi:10.1007/s10854-014-2481-2. [8] H.I. Humburg, M. Acosta, W. Jo, K.G. Webber, J. Rödel, Stress--dependent electromechanical properties of doped (Ba1−xCax)(ZryTi1−y)O3, J. Eur. Ceram. Soc. 35, 1209-1217 (2015). doi:10.1016/j.jeurceramsoc.2014.10.016. [9] W. Li, Z. Xu, R. Chu, P. Fu, P. An, Effect of Ho doping on piezoelectric properties of BCZT ceramics, Ceram. Int.38, 4353-4355 (2012). doi:10.1016/j.ceramint.2011.12.066. [10] Y.-R. Cui, X.-Y. Liu, C.-L. Yuan, X. Zhai, Y.-B. Hu, R.-W. Li, Preparation and Properties of Sm2O3Doped (Ba0.7Ca0.3)TiO3-Ba-(Zr0.2Ti0.8)O3 Lead-free Piezoelectric Ceramics, J. Inorg. Mater. 27, 731-734 (2012). doi:10.3724/SP.J.1077.2012.11517. [12] T. Miki, A. Fujimoto, S. Jida, An evidence of trap activation for positive temperature coefficient of resistivity in BaTiO3 ceramics with substitutional Nb and Mn as impurities, J. Appl. Phys. 83, 1592-1603 (1998). doi:10.1063/1.366870. [13] R.N. Schwartz, B.A. Wechsler, Electron-paramagnetic-resonance study of transition-metal-doped BaTiO3 : Effect of material processing on Fermi-level position, Phys. Rev. B. 48, (1993). doi:10.1103/PhysRevB.48.7057. [14] H. Herrig, R. Hempelmann, Microemulsion mediated synthesis of ternary and quaternary nanoscale mixed oxide ceramic powders, Nanostructured Mater.9, 241-244 (1997). doi:10.1016/S0965-9773(97)90063-5. [15] R.N. Viswanath, S. Ramasamy, Preparation and ferroelectric phase transition studies of nanocrystalline BaTiO3, Nanostructured Mater. 8, 155-162 (1997). doi:10.1016/S0965-9773(97)00004-4. [16] L. Zhang, L. Zhong, C.L. Wang, P.L. Zhang, Y.G. Wang, Dielectric Properties of Ba0.7Sr0.3TiO3 Ceramics with Different Grain Size, Phys. Status Solidi A. 168, 543-548 (1998). doi:10.1002/(SICI)1521-396X(199808)168:2<54

Influence of calcium doping on microstructure, dielectric and electric properties of BaBi2Nb2O9 ceramics

Barium bismuth niobiate (BaBi2Nb2O9) ceramics modified by calcium were prepared by solid state synthesis and two-step sintering process. An impact of calcium substitution on the A site of perovskite block is presented. The investigations are focused on dielectric as well as electric aspects of the modification. The presented results reveal that the concentration of a space charge is not preserved, what is surprising due to the homovalent nature of the dopant and no reason for creating additional lattice defects and charges connected. However, not only the valence of ions, but also the calcium-oxygen and barium–oxygen bond strength should be taken into consideration. Since the calcium–oxygen bond is probably weaker the loss of the bismuth oxide is expected to increase with an increase in the calcium content. Such a scenario results in appearance of a large number of negative charge carriers connected with unsaturated oxygen ions

Electric and dielectric properties of (Ba0.6Pb0.4)TiO3 ceramics modified with special glass in the range of phase transition

Perovskite ceramics (Ba0.6Pb0.4)TiO3 modified with PbO-B2O3-Al2O3-WO3 special glass was prepared with the conventional mixed oxide method. X-ray diffraction analysis (XRD) of the obtained materials confirmed singlephase and pure tetragonal structure. The Rietveld method was used to determine unit cell parameters. Uniform deformation of the tetragonal parameter was observed with addition of the glass. Dielectric measurements revealed the remarkable influence of special glass admixture on the value of dielectric permittivity and dielectric losses, as well as the Curie temperature. However, the most important achievement of the investigations is obtaining a significant PTCR effect in the sample containing 6 wt.% of special glass admixture