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Lead-free piezoelectric 0.8625NaNbO 3 -0.1BaTiO 3 -0.0375SrZrO 3 (0.8625NN-0.1BT-0.0375SZ) ceramics were prepared by templated grain growth method with NaNbO 3 templates. High orientation degree of 88.42% was achieved in the textured ceramics, which showed excellent piezoelectric performance with the quality factor Q m of 48.14 and the piezoelectric coefficient d 33 of 315 pC/N after poling. The grain morphology, crystal structure, P - E hysteresis loop, domain structures, frequency dependence of dielectric constant and loss tangent of conventional and textured 0.8625NN-0.1BT-0.0375SZ ceramics were systematically studied. It is indicated that ceramic texturing can effectively improve the piezoelectric performance of the NN-based lead-free piezoelectric ceramics, which provides a promising and broad prospect for the urgent development and practical applications of NN-based systems. • A highly oriented 0.8625NN-0.1BT-0.0375SZ textured ceramic is obtained. • The NN template excels in inducing grain growth of texture ceramics. • The dwelling time evidently affect the orientation of textured ceramics. • The texture process effectively improve the piezoelectric properties of ceramics. [ABSTRACT FROM AUTHOR]

The introduction of acceptor dopants into perovskites is a common method for designing hard piezoelectric ceramics by forming defect dipoles. It is interesting to find that the doping effect of a few amount of MnO 2 in (Bi 0.5 Na 0.5)TiO 3 –BaTiO 3 lead-free ceramics significantly depends on the local symmetry. A conventional hardening effect corresponding to an obviously enhanced mechanical quality factor and a decreased piezoelectric coefficient can be generated in the tetragonal phase rich zone, rather than in the rhombohedral-rich zone, where a typically amphoteric characteristic can be observed unexpectedly. The result was well interpreted by means of the formation of a local random field as a result of the local symmetry-breaking effect of point defects after doping MnO 2 in addition to a traditional internal bias field as a result of the pinning effect of defect dipoles. Compared with tetragonal-rich ones, the obviously enhanced random field in rhombohedral-rich compositions tends to induce a weakening ferroelectricity, as evidenced by composition dependent normal ferroelectric-relaxor ferroelectric phase transition. This work provides a new understanding of how charged defects affect the domain stability in the matrix with different symmetries through the competition between random electric fields and internal bias fields. • The doping effect of Mn in BNT ceramics depends on the phase structure. • An amphoteric characteristic is found in rhombohedral phase zone unexpectedly. • Both local random fields and internal bias fields are induced by charged defects. • Local random fields originate from local symmetry-breaking effect of point defects. [ABSTRACT FROM AUTHOR]

Strontium doped hafnium oxide (Sr:HfO 2 ) ferroelectric thin films with strontium concentrations ranging from 0 to 20mol% were processed with inorganic hafnium source and strontium source using a chemical solution deposition technique. The co-existence of monoclinic phase and ferroelectric orthorhombic phase in the Sr doped HfO 2 thin film was confirmed by x-ray diffraction and high-resolution transmission electron microscopy results. The atomic force microscope measurements were adopted and the thin films showed crack-free surface. The intrinsic ferroelectricity of the doped HfO 2 thin films could be demonstrated by polarization–voltage hysteresis loops together with piezoelectric force microscope. The maximum twofold remnant polarization value of 3.02 μC/cm 2 with a coercive field of 2.0 MV/cm was achieved when the Sr content was 7.5 mol%. Meanwhile, the polarization didn't show obvious degradation until 10 7 electric cycles, indicating the good fatigue performance of the Sr:HfO 2 film. These findings indicate that it is a feasible way to prepare Sr:HfO 2 ferroelectric thin films via chemical solution deposition with inorganic salt precursors. [ABSTRACT FROM AUTHOR]

Dielectric capacitors are of urgently demand in modern micro-electric industry. The surface modified inorganic filler introduced to polymer matrix represents a promising avenue for the dielectric material's enhancement of energy storage density. To ease the electric field concentration of the composite induced by permittivity difference between ceramic fillers and polymer matrix, the specific dielectric fillers of TiO 2 nanowires modified BT particles were synthesized in this study. Gradient dielectric composite consisting of poly(vinylidene fluoride-co-hexafluoropylene) [P(VDF-HFP)] matrix ( ε r ∼10), TiO 2 shell ( ε r ∼40), and BaTiO 3 (BT) core ( ε r ∼1000) were focused to investigate the electric field contribution and interface polarization. The results revealed that the permittivity of the composites increased as a result of large interfacial polarization induced by the large specific surface area of the nanowires as compared to the composite with randomly mixed TiO 2 /BT fillers. The breakdown strength of the composite was slightly improved with 20 vol% fillers, attributed to the fact that the electric field intensification was weakened by the BT@TiO 2 /Dop gradient dielectric fillers. The composite could endure up to 10 6 times of field cycling at the applied cycling field and the leakage current density was rather low. The composites with 20 vol% fillers exhibited a discharged energy density of 2.8 J/cm 3 at a low electric field, which was much higher than that of the neat P(VDF-HFP). The findings of this research introduced a new inorganic particle with large specific surface area and gradient dielectric permittivity as filler in composite for energy storage application. [ABSTRACT FROM AUTHOR]

Ba 0.8 Sr 0.2 TiO 3 thin films with different concentrations of Co dopant (0–10 mol%) were deposited on Pt/Ti/SiO 2 /Si substrates by sol-gel method. The microstructure, surface morphology, dielectric and tunable properties of the films were investigated as a function of Co concentration. It was demonstrated that all the Co doped Ba 0.8 Sr 0.2 TiO 3 (BSTC) thin films exhibited dense microstructure with uniform crystal grains and the grain size of the BSTC films decreased with the increase of Co content. Both dielectric constant and loss decreased with the increase of Co dopant. It was proposed that the depressed dielectric loss in BSTC film originated from the reduction of intrinsic electrons by Co acceptor doping. Although tunability of the BSTC films was also reduced with the addition of Co dopant, a largest figure of merit of 4.5 was obtained in the BSTC film with 5 mol% Co dopant owing to the comparable tunability and low dielectric loss of the films, which made it an alternative source for potential tunable applications. [ABSTRACT FROM AUTHOR]

• KTaO 3 modified Na 0.5 Bi 0.5 TiO 3 ceramics are synthesized for dielectric and energy storage capacitors. • The dielectric constant variation of the 0.90NBT-0.10KT ceramic is less than 15% in the range of 29–390 °C. • A large discharge energy density W D of 2.8 J/cm3 and energy efficiency of η 80.4% are achieved for 0.80NBT-0.20KT ceramic. Nowadays, it remains a challenge to achieve a simultaneous improvement of dielectric constant, energy density, and temperature stability in dielectric ceramics. In this work, it was found that such drawback could be effectively resolved by using KTaO 3 to substitute Na 0.5 Bi 0.5 TiO 3. In (1- x)Na 0.5 Bi 0.5 TiO 3 - x KTaO 3 ceramics, the temperature coefficient of capacitance (TCC) of x = 0.10 composition is lower than 15% in the temperature range of 25–390 °C, with a high dielectric constant of 2008 and a low dielectric loss of 0.0044 at 150 °C. Meanwhile, a large discharged energy density of ~2.50 J/cm3 with the variation less than± 3% in 5–190 °C was obtained under a low electric field of 18 kV/mm in x = 0.20 composition, accompanied with a high energy efficiency of> 80%. These results reveal that this ceramic system is a promising candidate for temperature-stable dielectric and energy storage capacitors applications. [ABSTRACT FROM AUTHOR]

3D SiC-based lattices with aligned SiC whiskers were prepared via direct ink writing of SiC w /polycarbosilane (PCS)-based suspensions. Suspensions with different solid loading were prepared and used to investigate the morphology and printability of 3D SiC w /SiC lattices. Filaments with the morphologies of accumulation, coiling, meandering and straight were achieved with different printing height and speed. Higher printing height favored the formation of coiled filaments with longer periodic structure and increased amplitude. 3D lattices with straight filaments and good retention of shape were achieved only when applying a suitable printing parameters for SiC w /PCS-based suspensions with a solid loading of 62.3 vol%. The resulted 3D lattices with the porosity around 62% showed impressive bending and compression strength of 33.2 ± 5.2 MPa and 30.6 ± 4.3 MPa, respectively. The satisfactory properties of 3D SiC w /SiC lattices were contributed by the pullout of the aligned SiC whiskers. Furthermore, this 3D technique via the Polymer-derived Ceramics (PDCs) route allows the fabrication of large sized samples, which opens new opportunities for the fabrication of 3D structures with unique mechanical and functional properties in practical dimensions. • 3D SiC composites with high amount of SiC whiskers were prepared via direct ink writing. • Morphologies of filaments could be controlled using different printing parameters. • Uniformly dispersed and aligned whiskers in matrix resulted in satisfactory strength. [ABSTRACT FROM AUTHOR]