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Hybrid piezo/triboelectric technology is an emerging energy source that can continuously power small electronic devices by harvesting ambient mechanical energy and converting it into electricity. In this work, a high-performance hybrid piezo/triboelectric device was presented. The composite film was synthesized that co-doped BaTiO3 powders (BT) and reduced graphene oxide (rGO) embedded within a host material made of polydimethylsiloxane (PDMS). The hybrid device is made by mixing BT powders into the PDMS to form a series of composite films, ranging from 10% to 45% by wt.%. Additionally, 1–5 wt.% of rGO was loaded into fabricates 40BT/PDMS. The results show that the addition of rGO can improve the uniform dispersion of BT powder in the PDMS matrix. The 4 wt.% of rGO for 40BT/PDMS exhibited the optimal energy harvesting performance among all compositions, achieving notable output voltage and current. This work demonstrates a facile, low-cost approach for obtaining high-performance hybrid piezo/triboelectric by utilizing a composite film BaTiO3 and polymer (PDMS) modified with rGO. [ABSTRACT FROM AUTHOR]

This study focused on the rare-earth hetero-valent substituted perovskite BaMO3 (M = Ce, Pr and Tb) which expected to show magnetoelectric response. In general, diamagnetic feature is presented in the 4f0 BaCeO3 system down to 2 K which is chosen as a reference in the study while BaPrO3 (4f1) and BaTbO3 (4f7) display antiferromagnetic phase transition at TN = 11.7 and 33.2 K, respectively, measured by MPMS magnetometer. At high oxygen partial pressure and donor ion-substitution (Nb5+), the BaMO3 systems demonstrate a similar defect chemistry to titanate perovskite which compensated by Ba-vacancy. Dielectric relaxation is detected for the doublet (BaPrO3 and BaTbO3) at the antiferromagnetic phase transition region. In order to examine the magnetoelectric response, the 8 Tesla of magnetic field is applied to the samples during the dielectric measurement. BaTbO3 shows a modest magnetoelectric response around 0.2% at the antiferromagnetic phase transition while that of BaPrO3 is silent. The activation energies derived from Arrhenius equation are reported to be in the range of 0.2 − 0.6 eV. [ABSTRACT FROM AUTHOR]

Transparent, flexible, and high-performance triboelectric nanogenerator (TENG) from nature-derived materials are required for sustainable society development. However, low triboelectricity from natural material is generally observed. Tunable electronic band diagram (EBD) through facile manipulation is one of the efficient methods to promote the TENG output, requiring fundamental, in depth understanding. Herein, we employed the high quality, single crystal-like Ti2NbO7 nanosheets (NSs) with dual dielectric and semiconducting properties as filler for bacterial cellulose (BC)-based TENG. Several techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), ultraviolet—visible (UV—vis) absorption, energy dispersive X-ray spectroscopy (EDS), and synchrotron radiation X-ray tomographic microscopy (SRXTM) were applied to characterize the long-range structure, microstructure, optical properties, elemental composition, and three-dimensional (3D) distribution of components in the composites. The semi-transparent and flexible 5 vol.% Ti2NbO7 NSs/BC preserved the integrity of cellulose, contained well-dispersed nanosheets, reduced optical band gap (4.20 vs. 5.75 eV for BC), and increased surface roughness. The dielectric permittivity and conductivity increased with nanosheets content. Adding negatively-charged Ti2NbO7 NSs could regulate the charge affinity of BC composite via shifting of Fermi energy over that of Al. It is found that adding 5 vol.% NSs into the BC film improved electrical outputs (~ 36 V and ~ 8.8 µA), which are 2–4 times higher than that of pure BC, even when paired with Al which lies adjacent in triboelectric series. Our work demonstrated the method to enhance BC-based TENG performance through EBD regulation using multifunctional Ti2NbO7 NSs. [ABSTRACT FROM AUTHOR]

In this work, the effect of La2O3 doping (x = 0–1.6 wt%) on the phase formation, microstructure and electrical properties of (K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3 (KNLNTS) ceramics was investigated. These samples were fabricated by the solid-state combustion method using glycine as fuel. The KNLNTS ceramics doping with La2O3 powders were calcined and sintered at 750 °C and between 1100 and 1200 °C, respectively, for 2 h. From the X-ray diffraction (XRD) results, the ceramics had a pure perovskite phase with coexisting orthorhombic and tetragonal phases in all samples. The Rietveld refinement analysis suggested that the tetragonality increased with increasing La2O3 doping. The grain morphology of the ceramics exhibited a rather square shape. The average grain size and the density of the ceramics tended to decrease from 1.5 to 0.7 µm and 4.71 to 4.56 g/cm3, respectively, when increasing La2O3 contents from 0 to 1.6 wt%. The dielectric behavior of the ceramics degenerated with La2O3 doping. A decrease in the leakage current and saturated hysteresis loops were observed in the samples doped with La2O3 ≥ 0.8 wt%. [ABSTRACT FROM AUTHOR]

We employ dielectric spectroscopy and the complex electric modulus formalism to characterize electrical properties of the Ti0.8O2 nanosheets‒Ag nanoparticles‒cellulose filter paper composites, intended for use as a triboelectric nanogenerator. The addition of these fillers (5–17 atom% Ti and 1–6 atom% Ag) increases both the dielectric permittivity and AC conductivity while typically keeping the low loss tangent. The observed exponent to the frequency-dependent universal power law indicates the three-dimensional (3D) hopping mechanism in the composited films, contrasting with the 1D- or 2D-conduction in the ceramics. The electrical responses are also distinct from those of sole nanosheets, indicating some filler-matrix interactions. Electric modulus analyses indicate that the Ti0.8O2 nanosheets act as a charge generation/reservoir, while the Ag nanoparticles generate long-range conduction paths. The relaxation time increases with the dielectric nanosheets content but decreases with metallic nanoparticle content. In addition, these co-fillers decrease the dielectric heating but increases the refractive index of the films. The simple analyses reported herein could be applied to other composites, providing a better understanding on the role of diverse functional co-fillers. [ABSTRACT FROM AUTHOR]

Natural biopolymer materials have been of interest in wearable energy harvester technology, especially in biocompatible triboelectric nanogenerators (BTENGs), due to their biodegradable, biocompatible, nontoxic and excellent antibacterial properties. Nevertheless, obstacles concerning economical and biocompatible utilization of triboelectric nanogenerators (TENGs) continue to prevail. The natural biopolymer, chitosan (CS), is composed of a long biopolymer chain of N-acetyl glucosamine. It enables exciting opportunities for low-cost, biodegradable triboelectric nanogenerator (TENG) applications. However, the electrical output performance of CS based on TENGs is low when compared with devices constructed from synthetic polymers. Hence, to enhance electrical output performance, BaTiO3 nano-powders (BT-NPs) were embedded into the CS as dielectric material, in order to improve electrical properties by increasing the dielectric constant of the composite film. A flexible hybrid piezo/triboelectric nanogenerator, designed by BT-NPs embedded into CS (BT-NPs/CS) composite film, was constructed successfully. The effects of the BaTiO3 nano-powder (BT-NP) content on the output performance were explored systematically. The device with 5 wt% BT-NPs in CS, and a 160-μm-thick film, exhibited maximum open-circuit voltage (VOC) and transferred short-circuit current (ISC) of 110.8 V and 10 µA, respectively, as well as maximum power output of 431.8 µW. Practical and application demonstrations also were investigated, namely charged capacitors for storing energy, testing voltage stability and driving commercial LEDs. This work exhibited high electrical performance enhancement of BT-NPs/CS nanocomposite film, which demonstrated better material modification. [ABSTRACT FROM AUTHOR]

The immense potential of colossal dielectric materials for use in high-energy-density storage applications has driven much recent development and research. The discovering of such dielectric materials with the required high permittivity and low dielectric loss is still a highly challenging. Herein, the donor-acceptor co-doped TiO2 has been developed based on (Mg0.5W0.5)xTi1-xO2, (In0.5W0.5)xTi1-xO2 and (Ni0.5Nb0.5)xTi1-xO2; where x = 0.005–0.01, that manifests high permittivity (>104). The resulted permittivity attains the quadruple than that of pure TiO2 ceramic with low dielectric loss of ∼0.02 over a broad temperature range. This performance is corresponded to the electron-pinned defect-dipoles, providing the extra dielectric response to those of rutile TiO2 host ceramics. This research offers the way to develop functional colossal-dielectric materials by engineering complex defects into the bulk that will help for further discovery of promising new dielectric materials in future. [ABSTRACT FROM AUTHOR]

Wearable triboelectric nanogenerators (TENGs) for converting human mechanical energies into electricity are being investigated widely, because of their potentially diverse applications that come from wearable power supplied to multifunctional self-powered sensing. However, external influences, such as water or high humidity, seriously degrade the electrical output of TENGs. Therefore, a simple method was implemented for fabricating a water repellent fabric-based TENG for harvesting human mechanical energies. Polytetrafluoroethylene (PTFE) or SiO2 modified by trichloro(octadecyl)silane (OTS) were sprayed onto a polyester (PET) fabric surface to increase hydrophobicity. The PTFE and SiO2/OTS coated polyester fabrics exhibited excellent water repellency with a high-water contact angle of ∼144° and ∼153°, respectively. The surface morphology of the coated fabrics showed roughness with a granular structure, which was responsible for air entrapment that prevented water from penetrating the fabric. Furthermore, electrical output of conventional PET fabric-based TENG was found to improve with the deposition of PTFE particles on the fabric surface. By pairing the PTFE coated fabric with aluminum (Al) tape, in order to fabricate TENG, the device generated a maximum voltage of 10.2 V and short-circuit current of 0.20 µA, with a power output of 0.23 μ W/cm2, which is 14 times greater than that of SiO2/OTS coated fabric-based TENG. The process for achieving water repellent fabric is simple, and the coating materials are available. Thus, a water repellent fabric-based TENG is promising for large-scale production of wearable harvesters from power supplied to multifunctional self-powered sensing. [ABSTRACT FROM AUTHOR]

Lead-free Bi0.5(Na0.68K0.22Li0.10)0.5TiO3 + 0.003 mol Sm2O3 (BNKLT-Sm) ceramics were synthesized via the solid-state combustion technique with calcination temperatures between 750 and 850 °C and sintering temperatures between 1025 and 1100 °C for 2 h. The results showed that increasing the calcination temperature caused the percentage of perovskite phase and the particle size of the BNKLT-Sm powders increased. The BNKLT-Sm powder calcined at 800 °C displayed a pure perovskite structure without any impurity phases. The influence of the sintering temperature on the phase formation, microstructure and electrical properties of the ceramics was then investigated. All samples sintered at different temperatures possessed coexisting rhombohedral (R) and tetragonal (T) phases and the R phase became dominant when the sintering temperature increased. The microstructure of all ceramics showed a rectangular shape and anisotropic growth. The average grain size increased with increasing sintering temperature. Dielectric and ferroelectric behavior displayed relaxor characteristics in all samples. The maximum dielectric constant at Tm (εm) of 4777 and the highest remnant polarization (Pr) of 5.03 µC/cm2 were obtained by the densest ceramics (5.85 g/cm3), which was sintered at 1075 °C for 2 h. [ABSTRACT FROM AUTHOR]

Owing to their structural advantages over bulk polymers, porous 3D substrates possess immense potential in triboelectric energy generation. This work reports the effective effort to fabricate the porous structure of polydimethylsiloxane, also known as the sponge-PDMS, by a simple template method. The sodium chloride salt from commodity product is used to create the 300 μm size of pores within the PDMS elastomeric layers, turning affects to the mechanical deformability of the triboelectric nanogenerator (TENG). The inner face of those pores is composited with the PVDF-HFP particles as a piezoelectric fillers. The presence of those fillers can be confirmed and their distribution within porous PDMS is 3D visualized by the synchrotron radiation X-ray tomography. The spatial distribution of the PVDF-HFP made it possible to fabricate the piezo-embedded macroporous TENG with high output power of 7.84 μW, giving over 2-fold enhancement, compared with the sponge-PDMS and even more when compared with the flat PDMS film under the same mechanical force. [ABSTRACT FROM AUTHOR]