scholarly journals The influence of BaGeO3 on the properties of Ba(Ti1−xSx)O3 ceramics on the basis of sol-gel powders

2019 ◽  
Author(s):  
Roberto Köferstein
Keyword(s):  
Phase Transition ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Sintering Temperature ◽  
Sol Gel ◽  
Synthesis Method ◽  
Particle Sizes ◽  
Dielectric Measurements ◽  
Sintering Additive ◽  
Phase Transition Temperatures

Ba(Ti1−x−y SnxGey )O3 (BTSG-x-y; x = 0, 0.05; y = 0–0.05) powders were synthesized by a sol-gel (SG) method and for comparative purposes also by a mixed-oxide (MO) method. In this system, BaGeO3 functions as sintering additive. Due to smaller particle sizes of the SG powders a higher sintering activity was found, which resulted in reduced grain growth and in a more homogenous grain size distribution for the corresponding ceramics. The dependence on the paraelectric ⇆ ferroelectric phase transition, i.e. the phase transition temperature, thewidth of the transition region and completeness were examined by dielectric measurements,DTA as well as by SEM, EDX and XRD investigations with respect to the BaGeO3 content, synthesis method and sintering temperature. The phase transition temperatures of the SG ceramics are remarkably higher than those of the MO ceramics with the same nominal compositions. The reason is a lower tin concentration within the grains of SG ceramics as confirmed by EDX and XRD investigations. The presence of BaGeO3 in barium titanate–stannate system on the basis of a SG method caused an improved incorporation of tin in theBaTiO3 lattice.

Ferroelectric phase transition temperatures of self-flux-grown RbTiOPO4 crystals

2004 ◽  
Vol 26 (4) ◽  
pp. 465-470 ◽  
Author(s):  
M. Roth ◽  
N. Angert ◽  
M. Tseitlin ◽  
G. Schwarzman ◽  
A. Zharov
Keyword(s):  
Phase Transition ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Transition Temperatures ◽  
Phase Transition Temperatures

Electrical Properties of Pb(Mg1/3Nb2/3)-PbTiO3 Ferroelectric Single Crystal

2009 ◽  
Vol 421-422 ◽  
pp. 419-422
Author(s):  
Ghulam Shabbir ◽  
Seiji Kojima
Keyword(s):  
Phase Transition ◽  
Electrical Properties ◽  
Single Crystal ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Charge Carriers ◽  
Frequency Range ◽  
Thermally Activated ◽  
Phase Transition Temperatures ◽  
Ferroelectric Single Crystal

The electrical properties of [001]-oriented morphotropic phase boundary (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-33%PT) single crystal have investigated as a function of temperature and frequency. The ac-conductivity exhibited continuous dispersion at all temperatures and frequency range examined and was associated to the thermally activated space charge carriers and local off-centering of Ti4+ and Pb2+ ions. The variations in ferroelectric phase transition temperatures observed in the poled state were associated to the polarization fluctuations and phase co-existence.

Features of Crystal Structure and Ferroelectric Phase Transitions of KTiOPO4 Doped with Nb and Sb

2004 ◽  
Vol 443-444 ◽  
pp. 303-306
Author(s):  
S.A. Ivanov ◽  
Sergei Yu. Stefanovich ◽  
S.-G. Eriksson ◽  
V.I. Voronkova ◽  
T.Yu. Losevskaya ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Structural Features ◽  
Neutron Powder Diffraction ◽  
Compositional Variation ◽  
Phase Transition Temperatures ◽  
Linear Optical Properties ◽  
Ferroelectric Phase Transitions

The evolution of the crystal structures as a function of temperature of the new solid- solution KTiOPO4 (KTP) isomorphs, namely K1-xNbxTi1-xOPO4 and K1-xSbxTi1-xOPO4 have been studied by neutron powder diffraction below and above the ferroelectric phase transition temperatures. On the basis of the experimental data obtained the cation distribution, among the sublattices of this structure, and the distortion of the framework at the phase transition, have been discussed. The possible correlation between the non-linear optical properties and the dominant structural features tailored by compositional variation has also been studied.

scholarly journals Valence Electron Distributions in Ferroelectric Barium Titanate Nanopowders

2014 ◽  
Vol 70 (a1) ◽  
pp. C746-C746
Author(s):  
Yoshihiro Kuroiwa ◽  
Masashi Yamada ◽  
Eisuke Magome ◽  
Chikako Moriyoshi ◽  
Hiroshi Tanaka ◽  
...  
Keyword(s):  
Phase Transition ◽  
Ferroelectric Phase Transition ◽  
Short Range ◽  
Room Temperature ◽  
Valence Electron ◽  
Ferroelectric Phase ◽  
Particle Sizes ◽  
Short Range Repulsion ◽  
Valence Electrons ◽  
Perovskite Type

Barium titanate BaTiO3 is one of the most important perovskite-type electroceramics, which undergoes the phase transition at 1300C from cubic to tetragonal, and exhibits ferroelectricity at room temperature. The phase transition depends on the particle size. BaTiO3 powders with the particle sizes less than several tens of nanometers are known to show no phase transition and hence no ferroelectricity at room temperature. The size effect of BaTiO3 is the most important issue in designing small ceramic capacitors with high capacitance. Our group has been devoted to visualizing the electron density distributions of perovskite-type oxides by analyzing the synchrotron-radiation x-ray powder diffraction (SXRD) data measured at SPring-8 using the maximum entropy method (MEM)/Rietveld method [1, 2]. In this study, the distributions of valence electrons in the outer shells of atoms are derived accurately from the SXRD data of BaTiO3 nanopowders to prove the characteristic chemical bondings which govern the ferroelectric phase transition. The powder samples used were 500 and 35 nm in particle sizes. The former showed the phase transition whereas the latter showed no phase transition. The MEM valence electron density studies at 2000C in the cubic structure revealed the clear structural variations that the Ti-O covalent bonding is found in the 500 nm sample, while all the valence electrons are localized at the O sites in the 35 nm sample exactly like an ionic crystal. Ferroelectricity originates from the balance between the long-rage Coulomb force and the short-range repulsion force. The obtained results provide direct experimental evidence that the electron orbitals hybridization on the Ti-O bonds weakens the short-range repulsion force, and causes the second-order Jahn-Teller distortion on the TiO6 octahedron in the 500 nm sample. We consider that the Ti-O bonding in the prototype structure governs the ferroelectric phase transition temperature in BaTiO3.

scholarly journals Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering

2015 ◽  
Vol 05 (02) ◽  
pp. 1550011
Author(s):  
Seonhyeop Shin ◽  
Jae-Hyeon Ko ◽  
Shinya Tsukada ◽  
Yukikuni Akishige ◽  
Krystian Roleder ◽  
...  
Keyword(s):  
Phase Transition ◽  
Light Scattering ◽  
Lead Titanate ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Paraelectric Phase ◽  
Dielectric Measurements ◽  
Brillouin Light Scattering ◽  
Acoustic Damping ◽  
Lower Temperature

The elastic properties of KF-substituted perovskite lead titanate ( PbTiO 3) were investigated by dielectric measurements and Brillouin light scattering. The ferroelectric phase transition occurred at substantially lower temperature due to KF substitution, which was attributed to the modification of the covalency in Pb – O and Ti – O bonds. The longitudinal acoustic (LA) mode of KF-substituted PbTiO 3 showed a frequency softening in the paraelectric phase, which was accompanied by increasing acoustic damping. This indicated that polarization fluctuations responsible for the acoustic anomalies were enhanced by KF substitution.

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