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Processing of Electroceramic Materials for Advanced Applications
Kachlík, Martin ; Petzelt, Jan (oponent) ; Bartoníčková, Eva (oponent) ; Maca, Karel (vedoucí práce)
The doctoral thesis is focused on processing of advanced ceramic materials with interesting physical properties. The materials were prepared by solid-state resp. hydrothermal syntheses. The first investigated material described in this work is EuTiO3 perovskite ceramics. Absence of thermodynamic data of this system led to extensive experimental research of proper processing conditions. Three mixtures of different powder precursors (Eu2O3 with Ti2O3 resp. TiO2 – rutile or anatase) were homogenized by planetary ball mill and formed by isostatic pressure of 300 MPa. These cylindrical green bodies were sintered conventionally in reducing atmospheres (Ar + 7 % H2 resp. pure H2) or by Spark Plasma Sintering (SPS). The influence of the sintering technique, temperature, atmosphere composition and dwell time on final density and phase purity was discussed. The investigation resulted in successful processing of phase pure EuTiO3 ceramic with relative density higher than 95 % of theoretical density (%TD). According author’s best knowledge, it is up to now the best bulk EuTiO3 ceramic sample. The importance of this achievement is also declared by four publications in respected journals where the properties of these samples were presented. The infra-red reflectivity spectra of prepared materials were compared with data from literature. It was proven that only single phase samples with low content of porosity are suitable for establishing their real (undistorted) physical properties. The next research was aimed on processing of Eu0.5Na0.5TiO3 ceramics by hydrothermal syntheses (HTS). The HTS were performed in highly alkaline environment of NaOH resp. KOH solution at temperature range 220 – 250 °C. The experiments with varied precursors (EuCl3 and TiCl4) and reductant agent concentrations led to processing of pure Eu0.5Na0.5TiO3 perovskite ceramic powder with submicron cubic particles. Another titanate - MgTiO3 - was synthetized by solid-state reaction from MgO and TiO2 powder mixtures. The mixtures were mechanically activated in ball mill for 0, 10, 40, 80 resp. 160 min. The green bodies were formed by isostatic pressure of 300 MPa and sintered by two different approaches. The first batch of samples was sintered by two-step sintering technique at 1300 °C (30 min) and 1200 °C (20 h). The second set was sintered conventionally at 1300 °C resp. 1400 °C for 30 min and post-sintered by Hot Isostatic Press (HIP) at 1200 °C resp. 1280 °C. The phase pure MgTiO3 samples with relative density higher than 93 %TD were reached after post-sintering by HIP at 1280 °C for 3 hours in Ar atmosphere and pressure of 200 MPa. The last studied material was Ba(Ca)Ti(Zr)O3 lead-free piezoceramics, which was prepared by solid-state reaction from powder mixtures milled by planetary ball mill at different conditions. The pressure-less sintering of isostatically pressed bodies (300 MPa) at 1200, 1300, 1400 resp. 1500 °C for 1 h in air was performed. The processing condition needed for single phase perovskite Ba0.85Ca0.15Ti0.9Zr0.1O3 ceramics with required microstructure were studied. The single phase Ba(Ca)Ti(Zr)O3 sample with relative density 96 %TD was successfully prepared. Our results proved the importance of careful choice of the processing techniques and their variables for reaching of desired microstructure and phase composition of advanced electroceramics and therefore for proper evaluation of their physical properties.
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Studium vlastních a nevlastních mikrovlnných dielektrických ztrát pomocí teraherzové a infračervené spektroskopie
Tkáč, Ondřej ; Kamba, Stanislav (vedoucí práce) ; Petzelt, Jan (oponent)
Nazcv prace: Studium vlastnich a ncvlastm'ch mikrovlnnych diclcktrickych zlrat ponioci leraher/ove a inlVaeervene spcklroskopic Autor: Ondfcj Tkac Katcdra (Ustav): Oddelem dieleklrik, Fy/ikalni ustav, AV CR Vedouci bakalafske prace: RNDr. Slanislav Kamba. C'Sc., Na Slovance 2. Praha 8 e-mail vcdouciho: kTi Abstrakt: V prvni casli prace je strucnc popsana pfislusna tcoric, zejmena sc zde venujeme principu inlraeervene spcktroskopic a lltovacim modelurn, dale vysvelleni pojmii vlastni a ncvlastni dielcktrickc /traty a pojcdnavamc lake o diclektrikach a fcroeleklrikach. Pomoci Fouricrovy infraccrvenc spcktroskopic jsmc mcfili infraccrvcna speklra pri pokojovc Icplole v rozsahu 30 - 3000 cm"1. Spektra jsmc iltovali a vyslcdnou komplcxni permitivitu jsmc cxtrapolovali do mikrovlnnc ohlasti. To nam umo/.nilo odhadnout podil nevlaslnich dielckirickych /tral na celkovych mikrovlnnych zlralach. U kcramickcho Sry.^Ph^CciTiiiO.if, (.v =0 az 9) jsmc studovali vliv obsahu olova na diclektricke vlaslnosli. Zjistili jsmc, /c nahrada slroncia olovcm /pusobujc vzrust pcrmilivity a/ na nckolik lisic a vynucujc leroelcklricky prechod pro x>2. U perovskilu Ca7n].3Nh23-\VxO3 (.v=0 az 0,01) jsmc /koumali vliv obsahu vanadu na diclektricke vlaslnosli, /ejniena na kocllcicnl rcsonancnf Irckvcnce r/ . Dale jsmc studovali vliv...
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Study of electrical and dielectric properties of conducting polymers
Varga, Martin ; Prokeš, Jan (vedoucí práce) ; Petzelt, Jan (oponent) ; Pfleger, Jiří (oponent)
Název práce: Studium elektrických a dielektrických vlastností vodivých polymerů Autor: Mgr. Martin Varga Katedra: Katedra makromolekulární fyziky Vedoucí disertační práce: RNDr. Jan Prokeš, CSc., KMF MFF UK Abstrakt: Transport elektrického náboje v polyanilinu a polypyrrolu byl stu- dován s ohledem na jejich různou morfologii, dále pak v souvislosti s použitím různých oxidantů, různých dopantů a též s ohledem na další modifikace při je- jich přípravě. Mechanismus transportu náboje je diskutován v rámci kombi- nace různych modelů popisujících transport v neuspořádaných systémech. Tento přístup je vhodný z důvodu heterogenní struktury vodivých polymerů. Byl také studován vliv vody na vodivost, v dlouhočasové limitě je pro vzorky lisované do tablet navrženo vysvětlení jevu na základě difúzního modelu. Zkoumali jsme stabilitu polypyrrolových nanotrubek v silně zásaditých prostředích a také jejich stárnutí, a to pomocí stejnosměrných i střídavých měřicích technik. Vodivost stu- dovaných materiálů při jejich přirozeném stárnutí zůstává stejného řádu i po dvou letech, avšak při deprotonaci v silných alkáliích nebo při zrychleném stárnutí za zvyšených teplot klesá vodivost polymerů o několik řádů....
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Studium vlastních a nevlastních mikrovlnných dielektrických ztrát pomocí teraherzové a infračervené spektroskopie
Tkáč, Ondřej ; Kamba, Stanislav (vedoucí práce) ; Petzelt, Jan (oponent)
Nazcv prace: Studium vlastnich a ncvlastm'ch mikrovlnnych diclcktrickych zlrat ponioci leraher/ove a inlVaeervene spcklroskopic Autor: Ondfcj Tkac Katcdra (Ustav): Oddelem dieleklrik, Fy/ikalni ustav, AV CR Vedouci bakalafske prace: RNDr. Slanislav Kamba. C'Sc., Na Slovance 2. Praha 8 e-mail vcdouciho: kTi Abstrakt: V prvni casli prace je strucnc popsana pfislusna tcoric, zejmena sc zde venujeme principu inlraeervene spcktroskopic a lltovacim modelurn, dale vysvelleni pojmii vlastni a ncvlastni dielcktrickc /traty a pojcdnavamc lake o diclektrikach a fcroeleklrikach. Pomoci Fouricrovy infraccrvenc spcktroskopic jsmc mcfili infraccrvcna speklra pri pokojovc Icplole v rozsahu 30 - 3000 cm"1. Spektra jsmc iltovali a vyslcdnou komplcxni permitivitu jsmc cxtrapolovali do mikrovlnnc ohlasti. To nam umo/.nilo odhadnout podil nevlaslnich dielckirickych /tral na celkovych mikrovlnnych zlralach. U kcramickcho Sry.^Ph^CciTiiiO.if, (.v =0 az 9) jsmc studovali vliv obsahu olova na diclektricke vlaslnosli. Zjistili jsmc, /c nahrada slroncia olovcm /pusobujc vzrust pcrmilivity a/ na nckolik lisic a vynucujc leroelcklricky prechod pro x>2. U perovskilu Ca7n].3Nh23-\VxO3 (.v=0 az 0,01) jsmc /koumali vliv obsahu vanadu na diclektricke vlaslnosli, /ejniena na kocllcicnl rcsonancnf Irckvcnce r/ . Dale jsmc studovali vliv...
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Processing of Electroceramic Materials for Advanced Applications
Kachlík, Martin ; Petzelt, Jan (oponent) ; Bartoníčková, Eva (oponent) ; Maca, Karel (vedoucí práce)
The doctoral thesis is focused on processing of advanced ceramic materials with interesting physical properties. The materials were prepared by solid-state resp. hydrothermal syntheses. The first investigated material described in this work is EuTiO3 perovskite ceramics. Absence of thermodynamic data of this system led to extensive experimental research of proper processing conditions. Three mixtures of different powder precursors (Eu2O3 with Ti2O3 resp. TiO2 – rutile or anatase) were homogenized by planetary ball mill and formed by isostatic pressure of 300 MPa. These cylindrical green bodies were sintered conventionally in reducing atmospheres (Ar + 7 % H2 resp. pure H2) or by Spark Plasma Sintering (SPS). The influence of the sintering technique, temperature, atmosphere composition and dwell time on final density and phase purity was discussed. The investigation resulted in successful processing of phase pure EuTiO3 ceramic with relative density higher than 95 % of theoretical density (%TD). According author’s best knowledge, it is up to now the best bulk EuTiO3 ceramic sample. The importance of this achievement is also declared by four publications in respected journals where the properties of these samples were presented. The infra-red reflectivity spectra of prepared materials were compared with data from literature. It was proven that only single phase samples with low content of porosity are suitable for establishing their real (undistorted) physical properties. The next research was aimed on processing of Eu0.5Na0.5TiO3 ceramics by hydrothermal syntheses (HTS). The HTS were performed in highly alkaline environment of NaOH resp. KOH solution at temperature range 220 – 250 °C. The experiments with varied precursors (EuCl3 and TiCl4) and reductant agent concentrations led to processing of pure Eu0.5Na0.5TiO3 perovskite ceramic powder with submicron cubic particles. Another titanate - MgTiO3 - was synthetized by solid-state reaction from MgO and TiO2 powder mixtures. The mixtures were mechanically activated in ball mill for 0, 10, 40, 80 resp. 160 min. The green bodies were formed by isostatic pressure of 300 MPa and sintered by two different approaches. The first batch of samples was sintered by two-step sintering technique at 1300 °C (30 min) and 1200 °C (20 h). The second set was sintered conventionally at 1300 °C resp. 1400 °C for 30 min and post-sintered by Hot Isostatic Press (HIP) at 1200 °C resp. 1280 °C. The phase pure MgTiO3 samples with relative density higher than 93 %TD were reached after post-sintering by HIP at 1280 °C for 3 hours in Ar atmosphere and pressure of 200 MPa. The last studied material was Ba(Ca)Ti(Zr)O3 lead-free piezoceramics, which was prepared by solid-state reaction from powder mixtures milled by planetary ball mill at different conditions. The pressure-less sintering of isostatically pressed bodies (300 MPa) at 1200, 1300, 1400 resp. 1500 °C for 1 h in air was performed. The processing condition needed for single phase perovskite Ba0.85Ca0.15Ti0.9Zr0.1O3 ceramics with required microstructure were studied. The single phase Ba(Ca)Ti(Zr)O3 sample with relative density 96 %TD was successfully prepared. Our results proved the importance of careful choice of the processing techniques and their variables for reaching of desired microstructure and phase composition of advanced electroceramics and therefore for proper evaluation of their physical properties.
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