Modified PZT ceramics as a material that can be used in micromechatronics

Results on investigations of the PZT type ceramics with the following chemical composition: Pb0.94Sr0.06(Zr0.50 Ti0.50)0.99 Cr0.01O3 (PSZTC) which belongs to a group of multicomponent ceramic materials obtained on basis of the PZT type solid solution, are presented in this work. Ceramics PSZTC was obtained by a free sintering method under the following conditions: T sint = 1250 °C and t sint = 2 h. Ceramic compacts of specimens for the sintering process were made from the ceramic mass consisting of a mixture of the synthesized PSZTC powder and 3% polyvinyl alcohol while wet. The PSZTC ceramic specimens were subjected to poling by two methods: low temperature and high temperature. On the basis of the examinations made it has been found that the ceramics obtained belongs to ferroelectric-hard materials and that is why it may be used to build resonators, filters and ultrasonic transducers

The Pb(Fe1//2Nb1//2)O3Pb(Fe_{1//2}Nb_{1//2})O_3 Ferroelectromagnetic Ceramics in a View of Possibilities to be Used for Electric Transducers

The $PbFe_{1//2}Nb_{1//2}O_3$ (PFN) ceramics can be obtained by a lot of ways. There are a lot of methods and techniques to synthesize the PFN powder such as: reactions in the solid phase by one-stage or two-stage synthesizing method (the columbite method), molten salt synthesis, sol-gel, co-precipitation method and sintering of compacts from a loose mixture of powders. Each of them requires accuracy and precision to conduct a technological process, aiming at obtaining a product with the optimum parameters. In the work PFN specimens were obtained by one-stage synthesis methods using two different powder synthesizing techniques: by calcining (sintering of a loose mixture of the PFN powder) and as a result of sintering of pressed compacts from the PFN powder mixture at high temperature (pressing). The obtained specimens were subjected to X-ray and micro-structural examinations and tests of internal friction and dielectric properties. The tests showed that the ceramics obtained by the powder calcining method has better applied properties

Parameters of ceramics obtained on the base PZT used to build electroacoustic converters

Modifying the basic chemical compositions of converters, obtained on the base of two - component solid solutions of the PZT type, is possible by the use of suitable dopants. In the work the complex of electric parameters, such as: $k_{p}$, $\varepsilon$, $tg \delta$, $d_{31}, S_{E}^{11}, E_{C}, P_{r}$ was determined for five different compositions of ceramics of the PZT type, used to product electroacoustic converters. The samples to research were condensed by conventional ceramic sintering method, replacing partly the ions Pb$^{2 + }$ with ions Ba$^{2 + }$ or Sr$^{2 + }$. To basic chemical compositions of ceramic samples, hard: Mn$^{2 + }$ and Cr$^{2 + }$ or soft: Nb$^{5 + }$ dopants were introduced, too

Low frequency elastic and anelastic properties of Pb(Fe

Pb(Fe0.5Nb0.5)O3 is one of the well studied ferroelectric compound. However, different physical properties of this ceramics were investigated in details, mainly at temperatures in the vicinity of the Curie point, whereas many questions remain about the behavior of physical properties in a wide temperature range, the presence of other phase transitions, types of lattice defects and their effect on macroscopic characteristics, etc. The papers devoted to low frequency elastic and anelastic properties of Pb(Fe0.5Nb0.5)O3 are practically non-existant. Nevertheless, the study of internal friction could give valuable information about different kinds (point, linear and plane) of lattice defects and the changes in the properties of the different phases of investigating ceramics which are related with the several mechanisms measured by the mechanical resonance spectrometer [3]. It is difficult to obtain such results by any other method; moreover sometimes it is impossible at all. In the work, we present results of the measurements of low frequency internal friction Q-1, Young's modulus E, electric permittivity ε and dielectric loss of angle tgδ in the polycrystalline Pb(Fe0.5Nb0.5)O3 ceramic samples in order to understand a nature of lattice defect interactions and mechanism Q-1 at the phase transition in the Curie and Neel points

Internal friction phenomena in composites based on PZT-type ferroelectric powder and ferrites

The aim of the work was to determine the phenomena of internal friction (mechanical losses) occurring in ferroelectric-ferromagnetic composites created based on PZT-type ferroelectric powder and ferrite. The composites were obtained using ceramic powders – multi-component PZT-type solid solutions with ferroelectric properties. Their magnetic component included zinc-nickel powder Ni0.64Zn0.36Fe2O4. 30 × 10 × 1 mm3 test specimens were obtained using free sintering. Temperature Q -1(T) and amplitude Q -1(ε) internal friction dependencies were determined. Wide high temperature maxima were observed with regard to the internal friction temperature dependencies obtained for the tested specimens. The conducted measurements of amplitude (isothermal) dependencies of internal friction Q -1(ε) for the tested composites have allowed for interpreting the previously observed maximum on the temperature dependencies of internal friction

The temperature dependences of electromechanical properties of PLZT ceramics

The mechanical and electrical properties in lanthanum modified lead zirconate-titanate ceramics of 5/50/50 and 10/50/50 were studied by mechanical loss Q - 1, Young's modulus E, electric permittivity ε and tangent of dielectric loss of angle tgδ measurements. The internal friction Q - 1 and Young modulus E measured from 290 K to 600 K shows that Curie temperature TC is located at 574 K and 435 K (1st cycle of heating) respectively for ceramic samples 5/50/50 and 10/50/50. The movement of TC in second cycle of heating to lower temperature (561 K for 5/50/50 and 420 K for 10/50/50) has been observed. Together with Q - 1 and E measurements, temperature dependences of ε=f(T) and tgδ=f(T) were determinated in temperature range from 300 K to 730 K. The values of TC obtained during ε and tgδ measurements were respectively: 560 K for 5/50/50 and 419 K for 10/50/50. These temperatures are almost as high as the temperatures obtained by internal friction Q - 1 measurements in second cycle of heating. In ceramic sample 10/50/50 the additional maximum on internal friction Q - 1 curve at the temperature 316 K was observed

Code signals transmission using MFSK modulation in shallow waters

The paper presents an acoustic system for the transmission of digital data in shallow coastal waters of which multi-path propagation and intense reverberations are characteristic. To ensure a small error probability of moderate speed transmission, the system uses corrective codes and a technique of incoherent modulation MFSK (Mufti Frequency Shift Keying). To synthesise the transmission signal, estimate the spectrum of the signal received and code and decode the channels, a DSP processor was used. The paper includes the results of a computer simulation in which the system was put to work in the presence of Gaussian noise. The system was tested in shallow coastal waters and the results are discussed in the paper