Novel perovskite-type (1 − x)BaTiO3–xBiYbO3 solid solutions with x = 0.00–0.20 were synthesized using conventional solid-state reaction methods. A systematic structural change from ferroelectric tetragonal to pseudo-cubic phase was observed at about x = 0.050–0.051 at room temperature. Dielectric measurements revealed a gradual change from normal ferroelectric behavior to highly diffusive and dispersive relaxor-like characteristics, wherein the phase transition temperature shifted to a higher temperature with increasing frequency. With an increase in the BiYbO3 content, the nonlinearity of the (1 − x)BaTiO3–xBiYbO3 ceramic was weakened obviously. The bulk ceramics were characterized by high polarization maxima and low remnant polarization, which exhibit slim P–E hysteresis loops. The results demonstrate that the (1 − x)BaTiO3–xBiYbO3 ceramics are promising lead-free relaxor materials for energy storage applications.

BaTiO3–BiYbO3 perovskite materials for energy storage applications

Publisher Summary This chapter points out that naming of polybenzoxazine is very complex due to the rich variety of structures from similar raw materials available. The general overview of benzoxazine chemistry and polybenzoxazine properties is provided here. The benzoxazine chemistry offers the richest molecular design flexibility among all classes of polymers, thus leading to advances in many fields with tailored properties. Benzoxazines exhibit various unusual properties, such as near-zero shrinkage upon polymerization, fast development of properties at low conversions, very high char yield, and hydrophobicity and low dielectric constants, despite having many hydrophilic groups. The cross-linked polybenzoxazine derived from bisphenol-A and aniline-based monomeric benzoxazine (BA-a) is expressed as poly (BA-a). It states that Benzoxazine is a molecule where an oxazine ring is attached to a benzene ring. There are several benzoxazine structures depending on the position of the heteroatoms. It explains that if benzoxazine monomers crystallize is pure then it tends to retain a small amount of solvents and impurities rather tenaciously and thus purification can sometimes be difficult. Upon polymerization, polybenzoxazine exhibits amorphous structure, as they are cross-linked. The synthesized compound is subjected to thermally accelerated, cationic ring-opening polymerization with or without an added initiator. If the initiation takes place with a labile proton initiator, such as phenol, it leads to a polymer with a phenolic structure. On the other hand, if a nonlabile proton initiator, such as Lewis acid, is used to polymerize at a relatively low temperature, it could lead to an arylether structure. However, the arylether structure is thermally unstable and can undergo structural transformation to the phenolic-type at an elevated temperature.

Overview and Historical Background of Polybenzoxazine Research

Abstract In contrast to the comprehensive understanding of novel ferroelectric [i.e., relaxor ferroelectric (RFE) and antiferroelectric] behavior in ceramics, RFE and double-hysteresis-loop (DHL) behavior in crystalline ferroelectric polymers have only been studied in the past fifteen years. A number of applications such as electrostriction, electric energy storage, and electrocaloric cooling have been realized by utilizing these novel ferroelectric properties. Nonetheless, fundamental understanding behind these novel ferroelectric behaviors is still missing for polymers. In this feature article, we intend to unravel the basic physics via systematic studies of poly(vinylidene fluoride- co -trifluoroethylene) [P(VDF-TrFE)]-based terpolymers, electron-beam (e-beam) irradiated P(VDF-TrFE) copolymers, and PVDF graft copolymers. It is found that both the crystal internal structure and the crystal–amorphous interaction are important for achieving the RFE and DHL behaviors. For the crystal internal structure effect, dipole switching with reduced friction and nanodomain formation by pinning the polymer chains are essential, and they can be achieved through crystal repeating-unit isomorphism (i.e., defect modification). Physical pinning [e.g., in P(VDF-TrFE)-based terpolymers] induces a reversible, electric field-induced RFE↔FE phase transition and thus the DHL behavior, whereas chemical pinning [e.g., in e-beam irradiated P(VDF-TrFE)] results in the RFE behavior. Finally, the crystal–amorphous interaction (or the nanoconfinement effect) results in a competition between the polarization and depolarization local fields. When the depolarization field becomes stronger than the polarization field, a DHL behavior is observed. Obviously, the physics for ferroelectric polymers is different from that for ceramics/liquid crystals and can be largely attributed to the long-chain nature of semicrystalline polymers. This understanding will help us to design new ferroelectric polymers with improved properties and/or better applications.

Novel Polymer Ferroelectric Behavior via Crystal Isomorphism and Nanoconfinement Effect

Characterization and evaluation of rice husk ash and wood ash in sustainable clay matrix bricks

Amino-functional benzoxazine monomers have been successfully prepared. Several routes have been applied to incorporate amino group into benzoxazine structure. These approaches include reduction of the corresponding nitro-functional benzoxazines and deprotection of protected amino-functional benzoxazine monomers. Various approaches that allow primary amine groups to be prepared without damaging the existing benzoxazine groups have been evaluated. Tetrachlorophthalimide and trifluoroacetyl are found to be suitable protecting groups. In addition, a model compound of amide-functional benzoxazines is prepared from primary amine-functional benzoxazine. Fourier transform infrared spectroscopy (FTIR) and 1H and 13C nuclear magnetic resonance spectroscopy (NMR) are used to characterize the structure of the monomers. The polymerization behavior of amino-functional monomers and model compound are studied by differential scanning calorimetry (DSC).

Primary Amine-Functional Benzoxazine Monomers and Their Use for Amide-Containing Monomeric Benzoxazines

The dielectric and ferroelectric properties of ( x )Pb(Mg 1/3 Nb 2/3 )O 3 –(1 − x ) Pb(Zr 0.52 Ti 0.48 )O 3 (where x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) ceramics prepared by an oxide-mixing method are measured by means of an automated dielectric measurement set-up and a modified Sawyer-Tower circuit, respectively. The dielectric properties of the ceramics are measured as functions of both temperature and frequency. The results indicate that the dielectric properties of the pure-phase PZT and PMN are of normal and relaxor ferroelectric behaviors, respectively. The dielectric behaviors of the 0.1PMN–0.9PZT and 0.3PMN–0.7PZT ceramics are more of normal ferroelectrics, while the other compositions are obviously of relaxor ferroelectrics. In addition, the transition temperature decreases and the maximum dielectric constant increases with increasing PMN content in the system. The P – E hysteresis loop measurements demonstrate that the ferroelectric properties of the ceramics in PMN–PZT system change gradually from the normal ferroelectric behavior in PZT ceramic to the relaxor ferroelectric behavior in PMN ceramic. These results clearly show the significance of PMN in controlling the electrical responses of the PMN–PZT system.

Dielectric and ferroelectric properties of lead magnesium niobate–lead zirconate titanate ceramics prepared by mixed-oxide method

In this study, the magnetic hysteresis properties of the Ising model in an oscillating external magnetic field were evaluated using mean field analysis. The average magnetization over a full oscillating field-cycle, as a function of the field amplitude, field frequencies and temperature, was investigated. The dynamic phase transition boundaries between the dynamic ferromagnetic and paramagnetic phases were defined on the field amplitude and temperature plane for each field frequency, in order to study the effect of frequency on the hysteresis dynamic phase transition. For the results, the hysteresis behaviors across the dynamic phase transition boundary were observed using varying field frequencies. The frequency dispersion of the hysteresis area, the remanence and the coercivity were categorized into three distinct types. These phenomena can be explained through an understanding of the role of frequency in the alteration of the dynamic phase boundaries, something which results in anomalous hysteresis properties as a function of frequency.

Frequency dependence of the Ising–hysteresis phase–diagram: Mean field analysis

The dielectric properties of (1 - x)Pb(Zr 0 . 5 2 Ti 0 . 4 8 )o 3 - (x)Pb(Mg 1 / 3 Nb 2 / 3 )O 3 (when x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) ceramics prepared by an oxide-mixing method are determined by means of an automated dielectric measurement set-up. The dielectric constant and dielectric loss tangent of the ceramics are measured as functions of both temperature and frequency. The results indicate that the dielectric properties of the pure phase PZT and PMN are of normal and relaxor ferroelectric behaviors, respectively. The dielectric behaviors of the 0.9PZT-0.1PMN and 0.7PZT-0.3PMN ceramics are more of normal ferroelectrics, while the other compositions are obviously of relaxor ferroelectrics. However, with a higher degree of disorder the PMN-modified PZT shows more diffuse phase transition nature than the pure PMN. In addition, the transition temperature decreases and the maximum dielectric constant increases with increasing PMN content in the system. The rate of transition temperature change, however, depends significantly on the Zr/Ti ratio of PZT.

Effects of Pb(Mg1/3Nb2/3)O3 mixed-oxide modification on dielectric properties of Pb(Zr0.52Ti0.48)O3 ceramics

In this study, BiFeO₃-BaTiO₃ ceramics have been fabricated by a solid-state reaction method. The effects of BaTiO₃ content in the (1-x)BiFeO3-xBaTiO3 (x = 0.1, 0.2, 0.25, 0.3, 0.4, 0.5) system on crystal structure and magnetic, dielectric, and ferroelectric properties were investigated. Perovskite BiFeO₃ was stabilized through the formation of a solid solution with BaTiO₃. Rhombohedrally distorted structure (1-x)BiFeO₃-xBaTiO₃ ceramics showed strong ferromagnetism at x = 0.5. Dielectric and ferroelectric properties of the BiFeO₃-BaTiO₃ system also changed significantly upon addition of BaTiO₃. It was found that the maximum dielectric and ferroelectric properties were exhibited in the (1-x)BiFeO₃-xBaTiO₃ system at x = 0.25. This suggested the morphotropic phase boundary (MPB) with the coexistence of both rhombohedral and cubic phases of the (1-x)BiFeO₃-xBaTiO₃ system at x = 0.25.

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Pitak Laoratanakul

Papers

Dielectric and ferroelectric properties of lead magnesium niobate–lead zirconate titanate ceramics prepared by mixed-oxide method

Frequency dependence of the Ising–hysteresis phase–diagram: Mean field analysis

Effects of Pb(Mg1/3Nb2/3)O3 mixed-oxide modification on dielectric properties of Pb(Zr0.52Ti0.48)O3 ceramics

Fabrication and characterization of (1-x)BiFeO3-xBaTiO3 ceramics prepared by a solid state reaction method

Phase formation and dielectric properties of bismuth sodium titanate-potassium sodium niobate ceramics