Authors:M. Roy, Praniti Dave, Shiv Barbar, Sumit Jangid, D. Phase, and A. Awasthi
The polycrystalline ferroelectric compounds of general formula Pb1−XBaXTiO3 with X = 0.00, 0.1, 0.2 and 0.5 were prepared by high temperature solid-state reaction technique using high purity oxides and carbonates.
The compounds formation was confirmed by X-ray diffraction and all the X-ray peaks were indexed with tetragonal structure
of space group P4mm. Morphology and particle size of the compounds were obtained using scanning electron microscopy. Ferroelectric phase transition,
enthalpy change, and specific heat of the compounds were obtained using modulated differential scanning calorimetry. It was
observed that the phase transition temperature decreased linearly with the increase of substitution concentration.
Authors:Praniti Dave, M. Roy, Shiv Barbar, and Sumit Jangid
The polycrystalline ceramic samples of general formula Pb1−XCaXTiO3 with X = 0.00, 0.1, 0.2 and 0.3 have been synthesized by standard high temperature solid state reaction method using high purity
oxide and carbonates. The formation of the single phase compounds have been checked by X-ray diffraction technique. The Modulated
Differential Scanning Calorimetry has been used to investigate the effect of substitution on the phase transition temperature
and the corresponding change on the enthalpy and other thermal parameters of the substituted compound/solid solutions. It
was observed that the phase transition temperature (Tc) decreases linearly with the increase of substitution concentration. The linear decrease in Tc with increase of substitution concentration may be useful for the eventual functionality of the materials for different ferroelectric
devices. The results are discussed in detail.
Authors:Ting Hu, Huanling Kong, Lie Chen, Yiwang Chen, Fan Li, and Daijun Zha
chain polymers, and few side-on-fixed conjugated polymers have been studied except the recent reports [ 10 , 12 ].
When an electric field is employed as an external force, ferroelectric liquid crystalline (FLC) are more desirable than ordinary
Thermal properties of three ferroelectric liquid crystals, namely: 3-octyloxy-6-[2-fluor-4-(fluoroctyloxy)phenyl]-pyridine (FFP), 3-(3-fluor-nonyl)-6[4-heptyloxyphenyl]-pyridine (FNHPh-P), 4-[(S,S)-2,3-epoxyhexyloxy]phenyl 4-(decyloxy)benzoate (EHPhDB) were studied using heat flux differential scanning calorimetry method. All the transitions expected in this compounds, except the SmC*-SmA* and SmC*-S3 transitions, were detected in the DSC curves. The temperatures of the phase transitions and the enthalpy changes associated with them were determined. The transition from the liquid crystalline to the crystalline state showed significant hysteresis for all three compounds studied. The following transitions: SmA*-Is, SmG*-SmC* for FNHPh-P, N*-Is for EHPhDB, N*-Is and SmC*-N* for FFP also showed a small hysteresis basing on which first-order character of all the above transitions was implied. All three substances studied in this work are characterized by a complex polymorphism in the solid state.
Dielectric relaxation and thermal transitions in β-PVDF have been investigated by Thermo-Stimulated Current spectroscopy and
Differential Scanning Calorimetry respectively. A comparative study of spectra and thermograms has been performed.
The relaxation mode associated with the glass transition of the true amorphous phase is characterized by relaxation times
obeying a compensation law due to cooperative molecular movements. A conformationally disordered structure is proposed for
β-PVDF to explain thermal events occurring around 60°C. Ageing of ferroelectric properties of β-PVDF has been associated with
cooperative molecular movements liberated largely below the melting point.
Authors:Dusanka Ž. Obadović, Anikó Vajda, Maya Garić, A. Bubnov, Vera Hamplová, M. Kašpar, and Katalin Fodor-Csorba
Thermal properties of a homologous series of ferroelectric liquid crystals S-(-)-[4-(2-n-alkoxy-propionyloxy)]biphenyl-4'-[n-alkoxy-(3,5-dimethyl)]benzoate have been investigated by polarizing optical microscopy and differential scanning calorimetry. The mesophases were identified and confirmed by X-ray too. Three binary mixtures were prepared from the individual homologues. In one of the mixtures (Mix1), the ferroelectric SmC* phase has broadened and became enantiotropic. This mesophase remained monotropic in the other two mixtures (Mix2, Mix3). The chiral nematic N* phase did not appear in Mix1, but remained monotropic for the other two mixtures. Two molecular parameters, the layer spacing and the average intermolecular distance have been calculated from the X-ray results for the homologues and their mixtures. An intercalated tail-to-tail packing of molecules was found both in the single compounds and their mixtures resulting in the layer spacing about half of the molecular length of the single compounds.
The study presents results of examination on Na0.5Bi0.5TiO3 (NBT) ferroelectric synthesis through intermediate binary compound Bi4Ti3O12 (BIT). The first stage of the study related to obtaining BIT from oxide precursors, i.e. Bi2O3 and TiO2. The second stage included obtaining NBT from Bi4Ti3O12, Na2CO3 and TiO2. Two polymorphic modifications of TiO2 (anatase, rutile) and diversified initial homogenization of raw material batches were applied during examination.
Authors:Dariusz Bochenek, Małgorzata Płońska, Julian Dudek, and Zygmunt Surowiak
Results of investigations on selected ceramic ferroics and multiferroics by TA method were presented. The authors of the work
used the thermal analysis both to optimize a process of producing the ceramic ferroics and multiferroics and to examine phase
transitions in that type of materials. In the case of synthesis of the ferroics and multiferroics as a result of sintering
of a mixture of simple oxides, the TA method enables to determine the optimum synthesis temperature and temperatures of re-crystallization
and disintegration of compounds and solid solutions. In the case of the sol–gel method, temperatures of dehydratization, burning
of an organic phase, and crystallization of an amorphous powder formed from the residual gel were determined by the TA method.
The TA method was also used to control a process of compacting and sintering the powders at high temperatures (Ts > 1,200 K), thus in a process of ceramic specimen formation. During rapid phase transitions, the ferroelectric specimens
of a first type emit (in the cooling process) or absorb (in the heating process) so called latent heat of the phase transitions.
On the DTA courses, it may be manifested in a form of exo- or endothermic peaks in the Curie temperature area (TC). The test materials included the ferroelectric ceramics of composition x/65/35 PLZT (ferroic for x < 9 at%) and mixed bismuth oxide layered perovskites (M-BOLP) of composition Bi5TiNbWO15 with <m> = 1.5 and the mutliferroic Pb(Fe1−xNbx)O3 ceramics (PFN) and Bi5TiFeO15 (BTF).
Synthesis of potassium bismuth titanate ferroelectric by heating of mixtures prepared using oxide precursors, i.e. Bi2O3, TiO2 and K2CO3 was investigated. DTA, TG, XRD and SEM methods were used to study the formation of intermediate compounds and the final product.
Usage of associated homogenization and grinding of precursors mixture permits to decrease the temperature of formation of