Papers by Author: Lucjan Kozielski

Abstract: Several compounds with Aurivillius-type structure in the Bi₄Ti₃O₁₂-BiFeO₃ system with the general formula Bi_m+1Fe_m–3Ti₃O_3m+3 showing multiferroic properties arouse an increasing interest due to their wide potential applications in electronics. The powders composed of the Aurivillius phase with m=5, 7 and 9 were successfully prepared by the co-precipitation-calcination route. The powders were ground and sintered, obtaining dense polycrystalline materials. The dielectric properties of the sintered materials were studied over a wide range of temperature and frequencies. A strong softening of the magnetic properties took place at 410°C, which stayed in good correlation with the recorded changes of the tan δ asymmetry and fact that it did not induce any anomaly of the Curie temperature at 670°C, where phase transition of the ferroelectric properties was determined.

Abstract: PZT ceramic system with presence of La contents, have been proposed and prepared using sol gel sintering method for practical application of photostriction, which is the superposition of photovoltaic and piezoelectric effects. Such a ceramics produced by conventional mixing oxide method does not exhibit photostrictive properties due to the defects and inhomogeneous distribution of grains and pores. In this study, an investigated lanthanium(III) doped PZT ceramics were obtained by sol-gel technique from the organometallic precursors. It was found that fabricated material were effective in the enhancement of photovoltaic and photostrictive properties. Consequently, lanthanium influence deviation of piezoelectric parameters were studied as a function UV light illumination. For the determination lighting dependancy of the transformation parameters the resonant and antiresonant method was implemented. The improved Piezoelectric Transformer structure successfully changed gain characteristics proportionally to light intensity. The authors invention of a light driven output gain adjustment in Piezoelectric Transformers (PT) yields a novel “smart” multifunctional wireless device. This new created application area can be utilized in self-adopting shutters in photo cameras due to improved sensitivity to surrounding illumination conditions.

Abstract: For the growing interest in developing of more attractive multiferroic and magnetoelectric ceramics an alternative is a double-doped Pb(Zr1-_xTi_x)O₃- material with trivalent lanthanum and iron ions. Such material has a structure based on ABO₃ perovskite and properties depending on the chemical and structural composition. In the present work the results of the preparation and characterization of Fe³⁺- modified 9/65/35 PLZT ceramics have been reported. Two samples of Pb_0,91(La_1-zFe_z)_0,09(Zr_0,65Ti_0,35)_0,9775O₃ ceramics, for different Fe ions concentration (z = 0,0 and 0,5 at.%), were prepared from the MOM derived powders and sintered by the hot uniaxial pressing methods. To analyze the obtained ceramics properties the XRD, SEM and also application oriented dielectric and magnetic measurements were performed. The Fe³⁺ substitution at the La-site of PLZT has shown many interesting and unusual dielectric, piezoelectric and magnetic properties. The obtained material was proposed to implement into Piezoelectric Transformer structure to change gain characteristics proportionally to magnetic field intensity.

Abstract: Lanthanum-modified lead zirconate titanate (PLZT) ceramic materials have gained considerable attention due to their photostriction, which is the superposition of photovoltaic and piezoelectric effects. Functionally Graded Materials (FGM) implemented in construction of Piezoelectric Transformer (PT) can be used for direct converting photonic energy to electrical one by implementing photostrictive actuators with piezoelectric generator in one graded structure of piezoelectric transformer. Possible application in electronic industry needs thoroughly electrical and mechanical characterisation of this new FGM structure constructed from the PLZT/PZT material. Measurements presented in this work reveal high electrical anisotropy of this graded structure and the Impedance Spectroscopy (IS) proved to be a method capable to present such inequality in form of well separated semicircles. Additionally, dielectric measurements demonstrated that the characteristics of the graded structure are not a simply addition of starting materials parameters but are deeply influenced by a predominantly diffusion direction. Finally, additional nano-mechanical and -electrical methods are used for clarifying the complexity of the integration process of FGMs.

Abstract: Ferroelectric transparent variant ceramics can be used as a base material for photovoltaic driven piezoelectric transformers. This work reports on the preparation conditions of x/65/35 PLZT ceramics for x = 0, 2, 4, 8, 10, 16, 32 at.% La, via conventional mixed oxide method. The study gives a detailed account of the relationships between technology conditions and basic physical properties of obtained PLZT samples as potential material for transformers application.

Abstract: Piezoelectric transformer (PT) is a combination of piezoelectric actuator and transducer, which serve as the primary side and the secondary side respectively. In the present study the disk – shaped (of 20 mm in diameter and 0.6 mm in thickness), unipoled radial mode piezoelectric transformer based on modified PZT-type solid solution was custom designed and fabricated. Different input and output area ratios of the PT were studied, namely: 21, 4, 1. The electrical properties like voltage step-up ratio, output power and temperature rise were measured for PT operating at the first resonance frequency. With the driving voltage of 20 VRMS, the 3 W output power, 165 VRMS output voltage an temperature rise of 20 0C was obtained for PT with the input/output area ratio of 1. The voltage step-up ratio of 12.5 was obtained for PT with input/output area ratio of 21.

Abstract: The present study is devoted to synthesis and investigation of photoluminescence in the nanosized Bi4Ti3O12 (BTO) thin films. The randomly oriented BTO thin films have been obtained by a modified hybrid sol-gel process. Bismuth nitrate and titanium (IV) butoxide were used as the starting materials. The thin films were deposited on silicon, glass and stainless steel by spin coating and crystallized by the conventional thermal annealing at temperature T=650°C. Formation of the layer perovskite-type structure of the orthorhombic symmetry was confirmed by X-ray diffraction method. Conservation of the chemical composition was investigated by energy dispersive spectroscopy. The UV luminescence has been observed in BTO thin films at room temperature. Results on luminescence excitation and emission in bismuth titanate thin films are given in the present paper.