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The temperature dependent properties of (K,Na)NbO 3 -based piezoelectric materials enlightened us that the combination of compositions gradient could remedy the fluctuation of the electrical properties induced by the temperature variation. Then Li modified (K,Na)NbO 3 ceramics was chosen as target materials and a multi-layered structure containing a series of composition gradient layers was prepared via a conventional solid state reaction. The results of relative permittivity against temperature demonstrated that the as-called relaxor feature was observed in this proposed multi-layered structure and the change rate of the dielectric anomaly peak got evidently reduced. Besides, the field-induced strain varying less than 10% from the room temperature to 100 °C was also achieved in this layered-structure ceramics. Moreover, the investigation here could render us an important reference for designing ferroelectric materials to satisfy the diversified requirements in the functional device. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of the [0.852(Bi 0.5-x Sr x Na 0.5)-0.11(Bi 0.5 K 0.5)-0.038Ba]Ti (1-x) Ta x O 3 (designated as BNKT-BT-xTaSr) ternary system were prepared with co-doping of Ta5+ and Sr2+. The purpose of this study is to investigate the effects of co-doping of Ta and Sr element on the microstructure, phase structure electrical properties, and electrostrain behavior of BNKT-BT-xTaSr ceramics. With the increase of Ta5+ and Sr2+ doping, the transition temperature (T F-R) of the modified doped BNKT-BT-xTaSr ceramics from ferroelectric to relaxed phase decreases to below room temperature (RT). When x = 0.005, the BNKT-BT-xTaSr ceramics reached a large electrostrain of 0.46%(d * 33 = 657 p.m./V) at RT under an electric field of 7 kV/mm, which is caused by the transition from ergodic relaxor phase to ferroelectric phase under a high applied electrical field. In addition, the electrostrain is increased to 0.48% (d * 33 = 685 p.m./V) under the same electric field after the thermal aging process at 80 °C for two weeks. This study demonstrates that the A/B site co-doping could effectively improve the electrostrain properties of BNKT-BT-xTaSr ferroelectric ceramics. [ABSTRACT FROM AUTHOR]

The piezo-phototronic and pyro-phototronic effects are significant in terms of broadband photosensing. This review provides an overview of the latest progress in the emerging fields of broadband photosensing based on the piezo-phototronic and pyro-phototronic effects and sheds light on the future exploration of these two effects. [Display omitted] The piezoelectricity and pyroelectricity of third-generation semiconductor materials (such as ZnO, GaN, and CdS) distinguish them from traditional semiconductors and give rise to two novel effects: the piezo-phototronic effect and the pyro-phototronic effect. The piezo-phototronic effect is to use the piezoelectric polarization charges at the heterointerface to tune the electron-hole separation or recombination in optoelectronic processes. For the pulsed incident light, local generated heating results in a strong pyroelectric effect, which gives a high output voltage and current. This is the pyro-phototronic effect. In this review, we give a systematic introduction to the two effects. Following that, recent advances in piezo-phototronic and pyro-phototronic effects enhanced broadband photosensing, including applications of the piezo-phototronic and pyro-phototronic effects in broadband photodetectors and their synergy effect, are thoroughly summarized. Finally, a perspective is given regarding their future impacts. [ABSTRACT FROM AUTHOR]

Abstract: Lead-free piezoelectric ceramics (1− x)(0.98K0.5Na0.5NbO3–0.02LiTaO3)–x(0.96Bi0.5Na0.5TiO3–0.04BaTiO3) (KNN–LT–BNT–BT) with x =0–0.10 have been synthesized by a conventional sintering technique. All samples possess pure perovskite structure, showing room temperature symmetries of orthorhombic at x <0.02, and tetragonal at 0.05≤ x ≤0.10. A coexistence of orthorhombic and tetragonal phases in the composition range of 0.02≤ x <0.05 in this system is caused by the temperature of the polymorphic phase transition (PPT) decreasing to around room temperature but not the behavior of the morphotropic phase boundary (MPB). The samples near the coexistence region exhibit improved properties, which are as follows: piezoelectric constant d 33 =155pC/N, remnant polarization P r =24.2μC/cm2, and coercive electric field E c =2kV/mm. The results indicate that although this kind of ceramics displays good properties, further study is needed to promote the stabilities of the ceramics in order to utilize them in varying temperature environments. [Copyright &y& Elsevier]

In addition to x-ray diffraction, Raman spectrum measurements provide direct evidence of the tetragonal and orthorhombic phases coexistence in lead-free ceramics (1-x)K0.5Na0.5NbO3 (KNN)–xLiTaO3 when x equals 5 mol %. This is caused by the phase transition temperature between tetragonal and orthorhombic decreasing to around room temperature due to the Li and Ta doping in KNN, and not by constituting a region of morphotropic phase boundary as presented by most published papers. The results indicate that although this kind of ceramic displays good properties, it needs further study to verify if it is suitable to be used in a varying temperature environment. [ABSTRACT FROM AUTHOR]

Bi 4 Ti 3- x (Mg 1/2 W 1/2) x O 12 (BTMW100 x) ceramics were synthesized using a direct reaction method combined with a two-step sintering technique. The study systematically investigated the effects of B-site equivalent substitution of (Mg 1/2 W 1/2)4+ on BTMW100 x ceramics. The experimental results indicate that an appropriate amount of (Mg 1/2 W 1/2)4+ doping effectively reduces grain thickness, enhances grain distribution uniformity, and decreases the concentration of oxygen vacancies. Consequently, these modifications lead to improved piezoelectric performance while maintaining a high Curie temperature. Notably, Bi 4 Ti 2.95 (Mg 1/2 W 1/2) 0.05 O 12 (BTMW5) ceramics exhibit excellent piezoelectric properties and thermal stability, with a piezoelectric coefficient of 23 pC/N and a Curie temperature of 683 °C. These findings suggest that BTMW5 ceramics are promising candidates for high-temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]

Emerging 2D electronic materials have shown great potential for regulating and controlling optoelectronic processes. A 2D ferroelectric semiconductor coupled with the piezo‐phototronic effect may bring unprecedented functional characteristics. Here, a heterojunction photodetector made of p‐Si/V‐doped‐ferroelectric‐ZnO 2D nanosheets (FESZ‐PD) is fabricated, and the ferroelectricity‐enhanced piezo‐phototronic effect on the photoresponse behavior of the FESZ‐PD is carefully investigated. By introducing the ferroelectricity and the piezo‐phototronic effect, improved current rectification performance is achieved and the photoresponse performance of the heterojunction is enhanced in a broad spectral range. The applied voltage bias during measurement naturally causes ferroelectric spontaneous polarizations to align, resulting in a change in band structure near the interface and the local piezo‐phototronic effect. The modulated energy band promotes the generation, separation, and transportation efficiency of photogenerated carriers greatly. Compared with the Si/ZnO 2D nanosheets photodetector without ferroelectricity under strain‐free conditions, the photoresponsivity R of the FESZ‐PD increases by 2.4 times when applying a −0.20‰ compressive strain at +1 V forward bias. These results confirm the feasibility of coupling the ferroelectricity with the piezo‐phototronic effect in 2D ferroelectric materials to enhance the photoresponse behavior, which provides a good way to enable the development of high‐performance electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

CaBi 2 Nb 2 O 9 (CBN) with the Aurivillius phase has a high Curie temperature (T C) and remarkable fatigue resistance, which has great potential for application as high-temperature sensors. However, due to its low piezoelectric properties, its practical application remains a great challenge. In this paper, Ca 1- x Ce x Bi 2 Nb 2 O 9 ceramics were prepared by the direct reaction sintering (DRS) and conventional preparation (CP) methods, respectively. The experimental results indicate that Ce doping can increase the piezoelectric coefficient d 33 of CBN ceramics by about two times. Among them, the grain size of the samples prepared by the DRS method is finer and more uniform, and the d 33 value of DRS samples is about 3.6–9.4 % higher than that of CP samples. The DRS sample Ca 0·97 Ce 0·03 Bi 2 Nb 2 O 9 has a d 33 value of 18.9 pC/N, a T C of 948 °C, and a resistivity of 1.1 × 105 Ω cm at 600 °C. This study shows that DRS method is an effective densification method, which can prepare CBN-based ceramics with excellent comprehensive properties, and provides an innovative preparation route to explore CBN-based ceramics with excellent piezoelectric properties. [ABSTRACT FROM AUTHOR]

Defect dipoles in acceptor-doped perovskite-based ferroelectric ceramics play an important role in piezoelectric properties. In this work, the acceptor, such as Fe2+ and Cu+, -doped (K 0.5 N 0.5)NbO 3 (KNN) ceramics are fabricated in reduced atmosphere by the conventional solid-state reaction method. By tailoring the strongly polarized defect dipoles through poling and aging processes, ultrahigh electro-strain and large signal piezoelectric d 33 * values can be achieved. The electro-strains of 0.41% and 0.50% with d 33 * ~820 pm/V and ~1000 pm/V are obtained in Fe2+-doped and Cu+-doped KNN samples, respectively, which are 4-fold and 5-fold larger than that of pure KNN. Of particular interest is that the electro-strain and d 33 * values are found to improve with increasing temperature up to 140°C, accompanied with low strain hysteresis of 10%-20%. A detailed mechanism considering the interaction between defect dipole polarization and spontaneous polarization after poling and aging processes is proposed to explain the observed phenomena, which provides a good paradigm for achieving high piezoelectric response by defect engineering in perovskite-based ferroelectric ceramics. Image, graphical abstract [ABSTRACT FROM AUTHOR]

CaBi 2 Nb 2 O 9 (CBN) is a bismuth layered ferroelectric material with extremely high Curie temperature and low dielectric loss, which has great application potential in ultra-high temperature field. However, because of its low piezoelectric coefficient, its practical application still faces great challenges. This study successfully prepared Ca 1-x Ce x Bi 2 Nb 1.98 (W 2/3 Mn 1/3) 0.02 O 9 (x = 0–0.05) two-layer ferroelectric ceramics using direct-reaction sintering method. A pseudo tetragonal structure was successfully constructed near x = 0.02 using the substitution method of Ce4+ at site A, and W6+ and Mn4+ at site B, which altered the crystal structure of CBN based ceramics. The properties of CBN-based piezoelectric ceramics have been significantly improved by this modification. It has a higher piezoelectric constant (d 33 = 20.6 pC/N) and Curie temperature (T c = 950 °C), while having a lower dielectric loss (tan δ = 0.031 at 500 °C). In addition, CaBi 2 Nb 2 O 9 based piezoelectric ceramics also show excellent thermal stability. After annealing at 900 °C for 2 h, the d 33 value remained high at 19.2 pC/N, retaining about 93.2% of its original value. Therefore, these findings indicate that Ca 1-x Ce x Bi 2 Nb 1.98 (W 2/3 Mn 1/3) 0.02 O 9 is a high-temperature piezoelectric material with great potential. [ABSTRACT FROM AUTHOR]

This research investigated the effect of Bi4Ti3O12 (BiT) template particles size on the structure and piezoelectric properties of 〈001〉‐textured (Bi0.5Na0.5)TiO3 (BNT)‐based lead‐free piezoelectric ceramics. Results of X‐ray diffractometer analyses and scanning electron microscopy observations showed that high purity BiT template particles could be obtained with the KCl as the molten salt system. Highly 〈001〉‐textured (~87%) BNT‐based ceramics prepared with large size BiT templates (7.75 µm) exhibited a high inverse piezoelectric constant d33* (1100 pm/N), which was ∼3.38‐fold larger than that with 1.91 µm (325 pm/N). In addition, we have found that too small the template size can make it difficult to align the orientation of the template during the casting process, whereas too large the size can create problems such as too much hysteresis (∆S/Smax = 67%). This study has demonstrated that the use of high purity large size BiT template particles could provide a feasible route to fabricate BNT‐based textured ceramics with desired electro‐strain properties. [ABSTRACT FROM AUTHOR]

Bi 4 Ti 3- x (Mn 1/3 Ta 2/3) x O 12 piezoelectric ceramics were prepared by conventional sintering and direct-reaction sintering in this study. The effect of B-site Mn/Ta co-substitution and sintering method on the microstructure and electrical properties of Bi 4 Ti 3- x (Mn 1/3 Ta 2/3) x O 12 piezoelectric ceramics was systematically investigated. The experimental results show that the combination of high-valent Ta and low-valent Mn ions replacing Ti4+ ions reduce the concentration of oxide vacancy defects in BITMT ceramics. The direct-reaction sintering is a simpler preparation method and the prepared samples have more uniform grain distribution and higher density. The resistivity of the direct reaction sintered sample with x = 0.05 at 500 °C is 7.19 × 105 Ωcm, the residual polarization is 8.1 μC/cm2, and the temperature stability of the piezoelectric constant is good. Therefore, the present study suggests that the piezoelectric properties of Mn and Ta co-doping of BIT ceramics could be greatly enhanced via the direct-reaction sintering, which provides a promising alternative to the conventionally sintered for a more cost-effective preparation for BIT ceramics. [ABSTRACT FROM AUTHOR]

ZrO2 powders of various particle sizes (0.15, 0.7, 500 µm) were used to simulate loose powder bed sintering to prepare BF–BT piezoelectric ceramics. The phase structure, dielectric properties, ferroelectric properties, and piezoelectric properties were compared with the samples sintered by the conventional powder bed method (i.e., powder of the same composition as the sample). Results showed that the use of loose ZrO2 powder bed could improve the heat conduction rate and the sintering quality of bulk BF–BT piezoelectric ceramics. The XPS results showed that the samples sintered with 500 µm ZrO2 powder beds had the lowest concentration of Fe2+, exhibited the largest piezoelectric coefficients (d33 = 201 pC/N). In contrast, the sample sintered with a conventional powder bed under the same sintering conditions had a piezoelectric coefficient d33 of 156 pC/N. [ABSTRACT FROM AUTHOR]

The siliconboron carbonitride/graphene (SiBCN/GN) composites were designed and synthesized by the insertion of GN sheets into the ceramic network of polymer-derived SiBCN via liquid dispersion (SiBCN/GN-ld) and solid phase blending (SiBCN/GN-sp) at 1100 °C. The composites were used as anode materials in lithium-ion batteries, and their electrochemical performances were investigated. Electrochemical measurements showed that the SiBCN/GN-ld exhibited a first cycle discharge capacity of 844.2 mA h g −1 at a current density of 80 mA g −1 , which was higher than those of SiBCN/GN-sp, SiBCN, and GN anodes. The discharge capacity reduced to 347 mA h g −1 and remained in this range over 30 cycles. SiBCN/GN-ld anode contained Si 3 N 4 , SiC, BNC, and free carbon nanocrystals sites, and GN acted as layered base supporting the SiBCN cluster, thus resulting in improved chemical stability and chemical electronic conductivity. Therefore, the SiBCN/GN-ld showed the improved electrochemical performances that were attributed to the presence of GN. GN layers acted as the supporting layers to stabilize the SiBCN matrix and alleviate the expansion of material structure during charge–discharge cycle. Dependence of the electrochemical capacities of the SiBCN/GN composites on their compositions and structures indicated the promising potential to enhance the electrochemical performances of the materials through molecular design and/or the control of the material structure. [ABSTRACT FROM AUTHOR]

〈001〉 textured Ba 0.85 Ca 0.15 Ti 0.90 Zr 0.10 O 3 (BCZT) lead-free ceramics were fabricated by reactive-templated grain growth (RTGG) method using plate-like BaTiO 3 templates. Aligned plate-like BaTiO 3 particles grew at the expense of equiaxed matrix powder with random orientation with increasing sintering temperature, resulting in development of texture. Highly textured (texture fraction f =0.98) BCZT ceramics were prepared at first with a RTGG process. Development of texture was investigated during sintering. The influence of templates content on texture fraction and electrical properties of the textured BCZT ceramics were also studied. The textured ceramics shows high piezoelectric coefficient ( d 33 =455 pC/N) and dielectric properties ( ε r ~3500, tan δ ~0.010). [ABSTRACT FROM AUTHOR]

The structural, piezoelectric, ferroelectric, and dielectric properties of Mn-modified 0.7Bi 1.02 FeO 3 -0.3BaTiO 3 (0.7BF-0.3BT) lead-free piezoceramics prepared by direct reaction sintering (DRS) and conventional process (CP) were investigated in present study, respectively. Experimental analysis showed that the addition of small amounts of Mn4+ ions could enhance the piezoelectric properties of the BF-BT solid solution. The XPS results indicated that the DRS samples exhibited a higher ratio of Fe3+/Fe2+, and thus fewer oxygen vacancy defects. The piezoelectric constant d 33 of the 0.7BF-0.3BT-0.2mol%Mn ceramics prepared by DRS is as high as 172 pC/N, Curie temperature measured is 459 °C, and the relative dielectric constant ε r and dielectric loss tan δ at room temperature are 804 and 0.058, respectively, which are superior to those of the CP ceramics under the same sintering temperature. Therefore, the present study suggests that the dielectric and piezoelectric properties of Mn-doped BF-BT ceramics could be greatly enhanced via the DRS process, which provides a promising alternative to the CP for a more cost-effective preparation for BF-BT ceramics. [ABSTRACT FROM AUTHOR]

In high-power applications, since mechanical losses in piezoelectric devices always result in considerable heat generation, the temperature stability of the mechanical quality factor (Q m) is particularly crucial and should be considered in real piezoelectric applications. Here, we propose a poling-aging-repoling strategy to make the defect dipoles aligned with the poling direction as much as possible, thereby resulting in the strong pinning of ferroelectric domains. A giant internal bias field E i (11.6 kV cm−1 @ 1 Hz) and a high Q m (2074), accompanied by almost unchanged d 33 , are obtained in the composition of CuO-doped (K 0.48 Na 0.52) 0.94 Li 0.06 Nb 0.94 Ta 0.06 O 3 (KNNLT-Cu) ceramics with a diffused polymorphic phase transition. Furthermore, and this is more encouraging, the high electromechanical performance exhibits good temperature stability in the range from room temperature to 100 °C, suggesting that the thermal stability of Q m can be effectively improved by combining the strong pinning of defect dipoles with composition design and providing a way for the development and design of future high-power piezoelectric devices. By means of the poling-aging-repoling strategy. A giant internal bias field E i (11.6 kV cm−1 @ 1 Hz) and a high Q m (2074), accompanied by almost unchanged d 33 , are obtained in piezoceramic. [Display omitted] [ABSTRACT FROM AUTHOR]

This research explored the influence of Nb5+ doping on the electrical properties and microstructure of [0.852(Bi 0.5 Na 0.5)-0.11(Bi 0.5 K 0.5)-0.038Ba]Ti (1- x) Nb x O 3 (designated as BNKT-BT). The BNKT-BT samples were fabricated and the XRD results showed that the doping of Nb5+ ions induced a transformation from the coexistence of both rhombohedral and tetragonal phase to a single pseudo cubic phase. Also, the doping of Nb5+ ions caused the temperature of ferroelectric state-ergodic relaxor state transition to decrease below the room temperature (RT). The SEM observations showed that the Nb5+ doping had a minor effect on the grain size of BNKT-BT samples. In addition, the samples achieved a large electrostrain of 0.43% (d * 33 = S max / E max = 614 pm/V) under 7 kV/mm at RT. Moreover, the aging process employed at 80 °C for two weeks in air could effectively increase the electrostrain from 0.38% to 0.41% under 6 kV/mm (d * 33 = 683 pm/V) and reduce the strain hysteresis from 57% to 34%. These results indicated that the B site doping, combined with the aging process, could provide an effective way to enhance the electrostrain performance of lead-free piezoelectric ceramics. • Niobium ions as dopants can effectively destroy the long-range ferroelectric order of the BNKT-BT-based ceramics. • At room temperature, with the addition of niobium ions, the samples change from ferroelectric state to ergodic relaxed state. • Niobium ions doping and the aging process provide an effective means for the development of practical BNT-based ceramics. [ABSTRACT FROM AUTHOR]

As a promising energy harvesters, triboelectric nanogenerators (TENG) can be utilized to convert distributed energy into electric power, but the slow charge accumulation incorporated with the inevitable charge decay/leakage of conventional TENGs result in a low surface charge density and an inferior output performance, limiting their practical applications. Here, an effective strategy is proposed to realize high charge density by using a fast charge accumulation process on dielectric material with high relative permittivity. As a result, the charge density is tremendously improved to 2.20 mC m−2 on the poly(vinylidene fluoride‐trifluoroethylene) film. Meanwhile, the fast charge accumulation is highly conducive to reach a high charge density of 1.30 mC m−2 in a 90% relative humidity environment, which is ≈260 times that of a TENG with slow charge accumulation. This work not only provides a new insight into charge accumulation and equilibrium state, but also provides significant guidance on the performance optimization of TENG. [ABSTRACT FROM AUTHOR]

A series of HfO 2 -modified (Bi 0.475 Na 0. 405 K 0. 055 Li 0.015) 0.95 Ba 0. 05 Ti (1- x) Hf x O 3 (x = 0–0.015) lead-free ceramics were prepared. Results of detailed characterizations showed that the addition of HfO 2 had little influence on the grain size, and all of the samples showed the pure perovskite structure. As the Hf4+ content increases, the samples changed from the normal ferroelectric phase to the ergodic relaxor state at room temperature, and the ceramics with x = 0.01 showed a high electro-strain of 0.295% at 6 kV/mm. Therefore, this study provides a new insight into of how the HfO 2 addition influences the ferroelectric property of the BNT-based ceramics by B-site substitution. [ABSTRACT FROM AUTHOR]

Oxidation behaviors of SiC in the presence of some impurities are very important for the performance of SiC used in high temperature environments such as aerospace vehicles and nuclear reactors. In this study, the effects of NaF on the oxidation behaviors of SiC powder with grain sizes from 0.3~2 μm were investigated. NaF with contents of 0.2~10 wt.% was added to the 6H-SiC powder (~ 1 μm) and the mixtures were oxidized at 500~800 °C for 30 min in air atmosphere. Compared with pure SiC, enhanced oxidation was observed with the NaF addition as low as 0.2 wt.%. When the content of NaF was increased to 2.0%, the weight gain ratio of SiC reached 23.0% at the oxidation temperature of 700 °C, which was only 0.6% for pure SiC powder. In the TG analysis, the onset oxidation temperature for the SiC-2.0%NaF sample was significantly decreased to 570 °C. The weight gain was increased with the decrease of SiC grain size. The intensive oxidation was confirmed by SEM, TEM, XRD and XPS characterizations. The formation of free carbon during the oxidation process was demonstrated by XRD and Raman spectroscopy. New polytype of SiC of 15R and defects were formed in the 6H-SiC matrix after oxidation. The results showed that NaF could greatly accelerate the oxidation of SiC and played a very important role in the microstructure evolution of SiC. Possible mechanism for the effects of NaF on the oxidation behaviors of SiC was discussed. [ABSTRACT FROM AUTHOR]

In this study, plate-like Na 0.5 Bi 0.5 TiO 3 (BNT) templates with perovskite structure were obtained by two-step molten salt synthesis (MSS) method at a low temperature. Firstly, Bi 4 Ti 3 O 12 precursors were synthesized at 1030 °C in NaCl–KCl molten salt. Secondly, plate-like Na 0.5 Bi 0.5 TiO 3 particles with perovskite structure were obtained from plate-like layer-structured ferroelectric ceramic of Bi 4 Ti 3 O 12 by topochemical microcrystal conversion method. Result showed that excessive Na 2 CO 3 was beneficial to facilitate the low temperature synthesis. In the case of an excess of 30 mol% Na 2 CO 3 , plate-like BNT particles could be obtained by synthesis at temperatures ranging from 760 °C to 800 °C, which indicated a flexible processing route. Also, it has been observed that plate-like BNT particles show a high aspect ratio with 1 μm in thickness and 10–20 μm in length. These Na 0.5 Bi 0.5 TiO 3 plate-like particles can be good candidates for the preparation of lead-free BNT-based piezoelectric ceramics with oriented grain microstructure. [ABSTRACT FROM AUTHOR]

Texturing is an effective approach to improving the piezoelectricity of piezoelectric ceramics. In this work, <001> textured Li+‐doped 0.852Bi0.5Na0.5TiO3–0.11Bi0.5K0.5TiO3–0.038BaTiO3 ternary lead‐free piezoelectric ceramics are prepared by the reactive templates grain growth (RTGG) method. X‐ray diffraction (XRD) results demonstrate a high orientation degree of 77% along the <001> direction. Outstanding electro‐strain response, which is higher than most of reported BNT‐based textured ceramics, is achieved due to the contribution of oriented‐grains along the <001> direction. A large electro‐strain of 0.55% with a relatively low hysteresis is obtained at 6.5 kV/mm with corresponding large signal piezoelectric coefficient (d33∗) of 846 pm/V in the textured ceramics, which is 49% higher than that of the random ceramics. Besides, the electro‐strain could reach as high as 0.52%@5.5 kV/mm (d33∗ = 945 pm/V) at 100°C. These results indicate that the RTGG is an effective way to design high performance lead‐free piezoelectric materials. [ABSTRACT FROM AUTHOR]

Flexible and free-standing electrode materials are prerequisite and key components for next-generation flexible energy storage and conversion devices. However, it is still a chanllenge to fabricate these materials from a continuous, straightforward, and facile method. Herein, we report a flexible composite film with silicon oxides decorated on few-walled carbon nanotubes, which can be continuously fabricated and directly drawn from the hot zone of the reactor. The composite film can be readily used for electrochemical lithium ion storage with high and reversible specific capacity, good rate capability, and excellent cycling performance. These exceptional characteristics make it very promising for flexible energy storage and other emerging applications. A continuous, flexible, and free-standing composite SiO x /CNTs film has been fabricated by the one-step and direct-injection floating catalyst chemical vapor deposition method and utilized for high performance electrochemical lithium ion storage. The materials' very unique and favorable structural and compositional characteristics have resulted in high capacity, excellent rate capability, and good cyclability for lithium ion storage applications. Image 1 [ABSTRACT FROM AUTHOR]

Abstract The large temperature dependence of electro-strain for Bi 0.5 Na 0.5 TiO 3 (BNT)-based ceramics limits their practical applications. In this work, Li-doped BNT-based lead-free multi-layer piezoelectric ceramic actuators are prepared by solid-state reaction synthesis method. The multi-layer actuator structure is fabricated by gradient doping, in which each layer corresponds to different compositions, with enhanced temperature stability compared to the single-layer one. For specific composition, it could achieve maximum electro-strain value at a certain temperature. Therefore, the electro-strain of each layer in this BNT-based multi-layer actuator could compensate each other at different temperatures with improved temperature stability. Consequently, the electro-strain of the five-layer structure varies less than ∼12% when the temperature changes from 50 °C to 130 °C, and a large electro-strain of 600 pm/V could be obtained at 70 °C. This work provides an effective approach by gradient doping to broaden the use temperature range for BNT-based actuators with improved temperature stability. Highlights • The BNT-based gradient doping multi-layer structure actuator is prepared. • The temperature stability of the multi-layer ceramics is greatly improved. • The strain of the five-layer ceramics varies less than ∼12% from 50 °C to 130 °C. • A large electro-strain of 600 pm/V could be obtained for the five-layer ceramics. [ABSTRACT FROM AUTHOR]

By the traditional solid-state reaction method, Bi0.5(Na0.8K0.2)0.5Ti1−x(Fe0.5Nb0.5)xO3 (marked as BNKT-xFN; x = 0.00, 0.01, 0.02, 0.03 and 0.04) piezoelectric ceramics were fabricated, and the effects of FN substitution on the dielectric, ferroelectric, piezoelectric and electric field-induced strain performance were investigated. The relative dielectric permittivity and loss tangent reveal that the phase transition temperature between ferroelectric and ergodic relaxor phase is reduced from 90 °C to room temperature (RT), even below RT, with increasing FN content. Temperature dependence of polarization-electric field loops and strain-electric field curves exhibits that the ferroelectric order is disturbed gradually, and the ergodic relaxor phase forms with increasing FN content. A large unipolar strain of 0.42% and corresponding d33* (= Smax/Emax) of 642 pm/V for the sample with x = 0.04 are obtained under 6.5 kV/mm due to the phase transition from ergodic relaxor to ferroelectric. These results indicate that the (Fe0.5Nb0.5)4+ complex ion-modified BNKT-based ceramics would have great potentials for lead-free electromechanical actuator applications. [ABSTRACT FROM AUTHOR]

Abstract: Field emission of electrons usually requires high voltage (HV) of at least 100 V, which limits its applications due to the high cost, instability, portability issues, etc., of the HV instrument. Triboelectric nanogenerators (TENGs) have been developed to provide an HV of at least several kV for portable/mobile instrument, with controllability already demonstrated. Here, the field emission of electrons driven by TENG, namely, tribo‐field emission, is presented for the first time. The emission voltage and the charge transfer per cycle can be tuned and controlled by TENG. The current peak generated from TENG with limited charge transfer is demonstrated to be more favorable than the direct current HV source in terms of emitter protection. A unidirectional continuous emission current is achieved through the tribo‐field emission. A cathode‐ray tube can be powered by TENG, with hours of illumination demonstrated through only one sliding motion. Such approach can provide a potential solution for controllable, stable, and portable field‐emission devices without any additional external power sources. [ABSTRACT FROM AUTHOR]

Highly 〈001〉 textured (~ 81%) ternary BNT-BKT-BT ceramics are prepared by reactive templated grain growth (RTGG) method with plate-like Bi 4 Ti 3 O 12 particles as templates. Outstanding electric properties, which are both higher than state of art BNT-based ceramics, emerge in the aforementioned sample due to the grain orientation. For the textured ceramics, a high piezoelectric constant d 33 of 314 pC/N could be obtained, which is ~ 1.4-fold larger than that of a random one (221 pC/N). A high electro-strain response (~ 0.41%) is obtained at a low applied electric field (4 kV/mm) in textured ceramics, with the normalized strain d 33 ⁎ ( S max / E max ) = 1030 pm/V near the T F-R (the temperature of ferroelectric to ergodic relaxor state transition). Moreover, the evolution process of relaxor phases is studied. The texture technique also could improve the T F-R from 70 °C to 100 °C, enhancing the temperature stability. In addition, the polarization switching process in ferroelectric phase and ergodic relaxor state are analyzed in this work, respectively. [ABSTRACT FROM AUTHOR]

La 3+ and Nb 5+ co-doped 0.85Bi 0.5 Na 0.5 TiO 3 -0.11Bi 0.5 K 0.5 TiO 3 -0.04BaTiO 3 (BNT-BKT-BT) samples were prepared through conventional solid oxide route, and the effects of doping ions on the phase structure, electrical properties, and electro-strain behavior were investigated. The XRD results showed that La 3+ and Nb 5+ co-dopant induced a phase transition from coexistence of ferroelectric tetragonal and rhombohedral phase to a pseudocubic phase. With increasing dopant content, the normal ferroelectric-to-ergodic relaxor (FE-to-ER) transition temperature ( T F-R ) decreased down from 120 °C to room temperature (RT), even below RT. A large unipolar strain of 0.34% ( d 33 ∗ = S max /E max = 680 pm/V) was achieved under 5 kV/mm and the largest electro-strain of 0.46% was achieved under an applied electric field of 7.5 kV/mm at RT for x = 0.0050. Temperature dependence of both polarization loops and bipolar strain curves from room temperature to 160 °C were also studied, and the results suggested that the origin of the large strain is attributed to a reversible nonpolar isotropic ergodic relaxor state to polar anisotropic ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

0.8Bi 0.5 Na 0.5 Ti (1- x ) Nb x O 3 −0.2Sr 0.85 Bi 0.1 TiO 3 (BNT-SBT- x Nb, x = 0.00, 0.01, 0.02, and 0.03) piezoelectric ceramics were prepared by traditional solid state reaction and the influence of Nb substitution on the phase structure, ferroelectric, piezoelectric, and electric-field-induced strain properties in BNT-SBT ceramics were studied. XRD results exhibited that Nb 5+ ions could fully diffuse into BNT-SBT structure to form a solid solution when x = 0.01. P-E loops and S-E curves suggested that the ferroelectric phase transformed to ergodic relaxor state (FE-to-ER) with the increasing the amount of Nb additive, indicating the ferroelectric long-ranged order was disturbed by the excess of Nb. With increasing Nb doping, phase transition temperature from normal ferroelectric to ergodic relaxor (short for T F-R ) could be reduced from 120 °C to 40 °C. Furthermore, for sample with x = 0.01, the normalized strain d 33 * got a maximum value ~571 pm/V due to the phase transition from ergodic relaxor to ferroelectric (ER-to-FE) under electric field. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics doped with small amounts of elements usually cause significant improvement in piezoelectric properties. In this study, we prepared Ba 0.85 Ca 0.15 Ti 0.90 Zr 0.10 O 3 – x wt% ZnO (0 ⩽ x ⩽ 0.16) ceramics via a conventional solid-state reaction method. The evolution of domain structure, relaxor behavior, ferroelectric and piezoelectric properties with Zn doping was systematically investigated. The ceramics with x = 0.08 possess slender domain patterns and high domain wall density. The Ba 0.85 Ca 0.15 Ti 0.90 Zr 0.10 O 3 –8 wt% ZnO ceramics show maximum remnant polarization and spontaneous polarization ( P r = 10.14 μC/cm 2 , P s = 19.68 μC/cm 2 ). A giant piezoelectric coefficient of d 33 = 603 pC/N and high planar electromechanical coupling factor of k p = 0.56 were obtained for the sample of x = 0.08, showing the potential possibilities for lead-free piezoelectric application. [ABSTRACT FROM AUTHOR]

Textured Ca0.85(LiCe)0.075Bi4Ti4O15ceramics were prepared by reactive templated grain growth method using Bi4Ti3O12templates. The highly oriented Ca0.85(LiCe)0.075Bi4Ti4O15ceramics (f = 98%) were formed in situ topotaxially on the Bi4Ti3O12templates, which exhibit high piezoelectric properties (d33= 33 pC/N) compared with the randomly ceramics in Aurivillius-type bismuth layer structured ferroelectrics. The d33value of textured ceramics has excellent temperature stability when the temperature is below the 500°C. High Tc and DC resistance also illustrate that the textured Ca0.85(LiCe)0.075BiTi4O15ceramics can be a promising high-temperature piezoelectric application. [ABSTRACT FROM PUBLISHER]

Abstract: 〈001〉 textured Bi4Ti3O12 platelets with micro scale size were synthesized by a facile molten salt method. The photocatalytic activities of the as-prepared samples were measured with the photodegradation of methylene blue at room temperature under visible light irradiation. The Bi4Ti3O12 with the aspect ratio of 35 exhibited good absorption in the visible light region and the photodegradation against methylene blue was higher than that of anatase TiO2 reference, showing that the high degree of preferred {001} facets on the plate surface benefits the electronic transmission. In addition, the layer-pervoskite structure facilitates the mobility of the photogenerated carriers and hampers their recombination. The above results indicated that the large specific surface area of the as-prepared samples could attribute to the presence of a number of oxygen vacancies and then lead to the good photo-electric property. This work proposed an alternative way to tailor the structure of micro-sized platelets to get excellent properties comparable to the nano materials. [Copyright &y& Elsevier]

Ferroelectric Ba0.55 Sr0.4 Ca0.05 Ti O3 ( BSCT) ceramics with nano- Mg O additive have been prepared by typical electrical ceramic technology sintered at 950°C for 2 h. The influence of the additive content on the sintering behaviors of BSCT ceramics is investigated. The results show that the interactions of Mg O with BSCT and B2 O3- Li2 O liquid sintering additive help to form wetting boundaries for accelerating densification process, promote the grain growth of BSCT ceramic. The BSCT ceramic with 20 wt% nano- Mg O possesses uniform microstructure, high densification, and superior dielectric properties. The modification mechanism of nano- Mg O on BSCT ceramic is summarized as ' Mg O assisted wetting sintering model.' [ABSTRACT FROM AUTHOR]