In this paper, t mol% Nb2O5 doped x(Ba0.7Ca0.3)TiO3-(1-x)Ba(Zr0.2Ti0.8)O3[xBCT-(1-x)BZT-t mol% Nb2O5] lead-free piezoelectric ceramics were prepared successfully using a solid-state reaction technique. Firstly, the phase transition ofxBCT-(1-x)BZT ceramics were investigate, and it was found that 0.47BCT-0.53BZT sample shows a rhombohedral (R)-tetragonal (T) phase transition at room temperature near Morphotropic Phase Boundary and presents better ferroelectric and piezoelectric properties compared with the other component ceramics. On this basis, the crystal structure, surface morphologies and electrical properties of the Nb2O5 doped 0.47BCT-0.53BZT ceramic were studied in detail. It was found the grain size increases monotonously and the microstructure become more denser and homogeneous when Nb-doping concentration increases above t=0.3, and a maximum strain value of 0.132%

Purpose -The purpose of this paper is to investigate the effects of coupling agents on the structure and properties of the nanocomposite films and clarify their mechanism. Polyimide (PI)/Al 2 O 3 nanocomposite films were prepared using different coupling agents. Design/methodology/approach -Poly(amic acid) (PAA) was firstly synthesised from appropriate pyromellitic diannanocomposite and oxydianiline in N-dimethylacetamide. Calculated amount of nano-Al 2 O 3 particles modified by different coupling agents (KH550, KH560, KH570 and AE3012) were added to PAA solution by an ultrasonic-mechanical method and PI/nano-Al 2 O 3 film was fabricated by heat curing. The microstructure, thermal stability, mechanical properties and electric breakdown strength of the films were characterised. Findings -The addition of coupling agents could greatly improve the dispersion homogeneity of Al 2 O 3 nano-particles in PI matrix. Results of corresponding characterisations indicated that both the thermal stability and mechanical properties of PI/Al 2 O 3 nanocomposite film with KH550 were greater/better than others, while AE3012 could improve the electric breakdown strength. Research limitations/implications -In the present discussion, the effects of different coupling agents, KH550, KH560, KH570 and AE3012, were investigated. Results of this research work would be beneficial to an in-depth understanding on the relationship between microstructure and properties of PI composites, and further promote the development of the high-performance PI insulating materials. Originality/value -The four coupling agents, KH550, KH560, KH570 and AE3012, were firstly used to disperse the nano-Al 2 O 3 particles in PI matrix. The effects of coupling agents on microstructure and properties of composites were discussed by the authors in detail.

Purpose -The key purpose of this study was to investigate the effects of different ultrasonic irradiation times on the wettability and other properties of the resulting water-based coating. The subject water-based coating was prepared using water-soluble polyester and amino resins by ultrasonic oscillation. Design/methodology/approach -The coating was prepared by polymerising polyester and amino resins in water using ultrasonic oscillation. The coating was baked for 40 seconds at 350°C to coalesce and solidify the film. The contact angle, thermal stability and mechanical properties of the film, as well as the molecular weight (MW) and structure of the polyester resin, were determined. Findings -The contact angle of the coating was found to decrease with ultrasonic irradiation; the mechanical properties and thermal stability were not altered when the irradiation time was longer than 5 hours. The MW of the polyester initially decreased then increased and stabilized with ultrasonic irradiation. The structure of polyester molecule and aggregated state of the solidified coating were not changed by ultrasonic irradiation. Research limitations/implications -In the study reported here, the effects of different ultrasonic irradiation times were investigated. Results of this research could benefit in-depth understanding of the influence of ultrasonic treatment on polyester resins and polyester coatings and could further promote the development of water-based coatings. Originality/value -The contact angle of the water-based coating decreased by mechanical means. The effects of ultrasound on microstructure and properties of the coating and resin were discussed in detail.

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It is known that a crystal structure and symmetry determine the physical properties of materials. Lattice distortion can strongly affect the symmetry of the crystal structure. Polar materials show changes in polarization with temporal fluctuations of temperature due to the asymmetry. As a polar crystal, hemimorphite shows excellent pyroelectric properties. However, to date, there are a few studies on its intrinsic physical properties, and the mechanism of its pyroelectricity remains unclear. In this paper, single-crystal x-ray diffraction measurement was carried out to obtain the atomic positions at 100–400 K. Furthermore, the electric dipole moments of [ZnO4] and [SiO4] polyhedrons along a, b, and c axes have been calculated. The calculated pyroelectric coefficient derived from the intrinsic electric dipole moment was compared with the experimental measurement. The results indicate that the pyroelectric coefficients of hemimorphite at different temperatures mainly come from the variation of the electric dipole moment of [ZnO4] and [SiO4] polyhedrons along the c axis. The electric dipole moment changes as a function of temperature from 100 to 400 K, which is induced by the random lattice distortion. It is found that pyroelectricity is strongly correlated with the random lattice distortion. The establishment of the relationship between lattice distortion and pyroelectricity helps us to regulate the specific electrical parameters of the material, which may lead to future work in energy harvesting and further properties.