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Mechanical properties of doped piezoceramics based on BaTiO3
Zeman, Dominik ; Chlup, Zdeněk (referee) ; Drdlík, Daniel (advisor)
This master‘s thesis deals with study of basic physical, microstructural and mechanical properties of doped piezoceramic materials based on BaTiO3 prepared by electrophoretic deposition. The dopants used were rare earth oxides, i.e. Eu2O3, Er2O3, CeO2, Dy2O3 and Tb4O7 in amounts 1, 3 and 5 wt. %. The influence of dopants and their amount on density, phase composition, mean grain size, hardness, elastic modulus, fracture toughness, and flexural strength was examined. Suitable dopant choice enabled decrease in mean grain size and increase in relative density, hardness, elastic modulus, fracture toughness and flexural strength of sintered specimens. Relative densities up to 99 %, mean grain size below 1 m, hardness up to 13,1 GPa, elastic modulus up to 199 GPa, fracture toughness above 1 MPa·m1/2 and flexural strength above 115 MPa were achieved.
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Electrospinning and characterization of fibrous structure for piezoapplications
Svobodová, Anežka ; Kaštyl, Jaroslav (referee) ; Částková, Klára (advisor)
The master’s thesis deals with the preparation and characterization of PVDF-based composite fibrous layers prepared by electrospinning. Ceramic particles TiO2, BaTiO3 and BCZT were used as fillers. The fibers were prepared containing 10, 20, 30, 40 and 50% of these particles and then their morphology, piezoactive phase representation and dielectric characterization were characterized. The effect of the presence of particles on the fiber diameter and on the crystallinity fraction of the polymer was shown. Particle size significantly influenced their distribution in the fibers. Piezoelectric particles further influenced the content of electroactive phases beta and gamma. The highest proportion of electroactive phases was determined in BaTiO3 filled fibers, which reached up to 98%. For the BaTiO3 filled fibers, the dielectric constant values were also measured, which reached lower values than expected due to the high porosity of the prepared fibers The as-prepared fibers can be considered promising not only for piezoapplications, therefore, optimization of their preparation and measurement of electrical characteristics will be further studied.
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Fabrication and properties of doped piezoceramics based on BaTiO3
Mařák, Vojtěch ; Chlup, Zdeněk (referee) ; Drdlík, Daniel (advisor)
This diploma thesis deals with the preparation of doped piezoceramic materials based on BaTiO3 using electrophoretic deposition. Five rare earth oxides, i.e. Er2O3, Dy2O3, Eu2O3, Tb407 and CeO2, were used as dopants in amounts of 1, 3, and 5 wt. %. The prepared deposits were evaluated in terms of preparation methodology, high temperature dilatometry, X-ray diffraction analysis, relative density, mean grain size, hardness and fractographic analysis. The study of dilatometric curves described the sintering behavior and its changes at different material compositions. X-ray diffraction analysis revealed a tetragonal phase in all samples; the tetragonality of the BaTiO3 crystalline cell decreased with dopant content. By a suitable choice of dopant, it was possible to significantly increase the relative density of sintered samples, their hardness and at the same time prevent the samples from coarsening of the microstructure during heat treatment. A relative density up to 98 %, a mean grain size below 1 m and a hardness of over 10 GPa were achieved. Analysis of the fracture surfaces revealed that the fracture mode was transcrystalline for the most of studied materials; only the samples doped with cerium dioxide had fracture surfaces with both transcrystalline and intercrystalline fracture modes. Based on the obtained results, a suitable composition of the material for the intended use in a layered piezoceramic harvester was identified, which, in addition to the BaTiO3 layers, consists of functionally-protective Al2O3 and ZrO2 layers.
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Preparatin of dopped lead-free piezoceramic materials by non-conventional sintering methods
Žaludek, Jakub ; Kachlík, Martin (referee) ; Pouchlý, Václav (advisor)
Piezoceramics BaTiO3 doped with ZrO2 was studied in this thesis. Six different compositions were prepared from base powders of BaTiO3 and ZrO2. with 10, 20, 40, 60, 80 and 90 wt% ZrO2. These mixtures were sintered using convetional sintering method and by Spark Plasma Sintering. Resuting ceramic compacts were subjected to measuring of density, dielectric constant, permitivity, polarization P-E curves, piezoelekctric faktor, loss factor and dilatometric measurements. From these results can be said that i tis possible to create piezoceramic BaTiO3 doped by ZrO2 with relative density higher than 94 %t.d. and these ceramics can possess piezoelectric properties. Value of highest piezoelectrick factor 33=9 / was achieved with addition of 20 wt% ZrO2. Dilatometric measurements discovered effect of increasing ammount of ZrO2 in BaTiO3. Rising amount of ZrO2 had a lowering effect on initial sintering temperature and materials achieved higher relative densities. This was also true for samples sintered using SPS, where it was less obvious. Measuring of electrical properties discoverad electric conductivity for SPS sintered samples, which was most probably caused by carbon introduced into samples during SPS cycle.
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Synthesis and Characterization of Perovskite Nanostructures
Hricov, Štefan ; Zákutná, Dominika (advisor) ; Kalbáčová Vejpravová, Jana (referee)
The present Bachelor's thesis is focused on the improvement of the hydrothermal condi- tions for BaTiO3 nanoparticles synthesis to obtain better morphology, narrow size distri- bution, and high purity of the prepared product. Particular emphasis is on the influence of different parameters in reaction, such as co-solvent, co-surfactant, the ratio between oleic acid to oleylamine, and ex-situ sodium oleate, on the resulting structure and morphology of BaTiO3 nanoparticles. The structural purity was examined with powder X-ray diffraction with Rietveld refinement to obtain and follow changes in lattice parameters and coherent domain sizes. Moreover, from the refinement of PXRD patterns, the rough estimate of a synthesis by-product (BaCO3) abundance was extracted. Furthermore, implementing the spherical harmonics function within the Rietveld refinement allowed us to access the average nanocrystallite shapes with direction-dependent crystallite sizes. The crystallite shapes and sizes were compared with the physical nanoparticle size obtained from trans- mission electron microscopy experiments. The thesis is completed with attenuated total reflectance Fourier-transform infrared spectroscopy spectra, which gave us insight into the attachment of the oleic acid at the nanoparticle surface. Keywords: BaTiO3,...
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Electrospinning and characterization of fibrous structure for piezoapplications
Svobodová, Anežka ; Kaštyl, Jaroslav (referee) ; Částková, Klára (advisor)
The master’s thesis deals with the preparation and characterization of PVDF-based composite fibrous layers prepared by electrospinning. Ceramic particles TiO2, BaTiO3 and BCZT were used as fillers. The fibers were prepared containing 10, 20, 30, 40 and 50% of these particles and then their morphology, piezoactive phase representation and dielectric characterization were characterized. The effect of the presence of particles on the fiber diameter and on the crystallinity fraction of the polymer was shown. Particle size significantly influenced their distribution in the fibers. Piezoelectric particles further influenced the content of electroactive phases beta and gamma. The highest proportion of electroactive phases was determined in BaTiO3 filled fibers, which reached up to 98%. For the BaTiO3 filled fibers, the dielectric constant values were also measured, which reached lower values than expected due to the high porosity of the prepared fibers The as-prepared fibers can be considered promising not only for piezoapplications, therefore, optimization of their preparation and measurement of electrical characteristics will be further studied.
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Preparatin of dopped lead-free piezoceramic materials by non-conventional sintering methods
Žaludek, Jakub ; Kachlík, Martin (referee) ; Pouchlý, Václav (advisor)
Piezoceramics BaTiO3 doped with ZrO2 was studied in this thesis. Six different compositions were prepared from base powders of BaTiO3 and ZrO2. with 10, 20, 40, 60, 80 and 90 wt% ZrO2. These mixtures were sintered using convetional sintering method and by Spark Plasma Sintering. Resuting ceramic compacts were subjected to measuring of density, dielectric constant, permitivity, polarization P-E curves, piezoelekctric faktor, loss factor and dilatometric measurements. From these results can be said that i tis possible to create piezoceramic BaTiO3 doped by ZrO2 with relative density higher than 94 %t.d. and these ceramics can possess piezoelectric properties. Value of highest piezoelectrick factor 33=9 / was achieved with addition of 20 wt% ZrO2. Dilatometric measurements discovered effect of increasing ammount of ZrO2 in BaTiO3. Rising amount of ZrO2 had a lowering effect on initial sintering temperature and materials achieved higher relative densities. This was also true for samples sintered using SPS, where it was less obvious. Measuring of electrical properties discoverad electric conductivity for SPS sintered samples, which was most probably caused by carbon introduced into samples during SPS cycle.
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Mechanical properties of doped piezoceramics based on BaTiO3
Zeman, Dominik ; Chlup, Zdeněk (referee) ; Drdlík, Daniel (advisor)
This master‘s thesis deals with study of basic physical, microstructural and mechanical properties of doped piezoceramic materials based on BaTiO3 prepared by electrophoretic deposition. The dopants used were rare earth oxides, i.e. Eu2O3, Er2O3, CeO2, Dy2O3 and Tb4O7 in amounts 1, 3 and 5 wt. %. The influence of dopants and their amount on density, phase composition, mean grain size, hardness, elastic modulus, fracture toughness, and flexural strength was examined. Suitable dopant choice enabled decrease in mean grain size and increase in relative density, hardness, elastic modulus, fracture toughness and flexural strength of sintered specimens. Relative densities up to 99 %, mean grain size below 1 m, hardness up to 13,1 GPa, elastic modulus up to 199 GPa, fracture toughness above 1 MPa·m1/2 and flexural strength above 115 MPa were achieved.
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