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Nonlinear mono-stable and multi-stable piezoelectric energy harvesters have attracted a lot of attention owing to their broadband frequency spectra and excellent energy harvesting performance. Herein, two types of nonlinear mono-stable, bi-stable, tri-stable, and quad-stable piezoelectric energy harvesters using cantilever structure and magnetic interaction are compared and analyzed. Based on the magnetizing current method, the magnetic force equations are obtained. Calculation results demonstrate that the stability of these harvesters is dependent on the equivalent linear elastic force and the vertical magnetic force. The equilibrium point occurs when the equivalent linear elastic force equals to the vertical magnetic force. The relationship between the number of stable equilibrium points E S and the number of the intersections of the two force curves N I is that E S= (N I + 1)/2. Experiments are carried out to verify the equivalent linear elastic force, vertical magnetic force, and the number of stable equilibrium points of the fabricated prototypes. The experimental results are consistent with the calculated results, which verifies the correctness of the stability mechanism. Moreover, it is found that the stability mechanism is also applicable to the harvesters with more stable equilibrium points, such as penta-stable and hexa-stable harvesters. This work reveals the stability mechanism of nonlinear mono-stable and multi-stable energy harvesters using cantilever structure and magnetic interaction, and provides technical methods for the design of multi-stable energy harvesters.

Ring-type 33-mode piezoelectric energy harvesters (PEHs) were fabricated using Pb(Zr,Ti)O3- and (Na,K)NbO3-based piezoelectric ceramics. The relationship between the output performance of the PEH and the piezoelectric properties of the ceramics was investigated. Ring-type PEHs were selected for this investigation because they can be mounted on a specimen holder at the same position, ensuring structurally reliable output performance. The × Q m / value, which was reported as a figure of merit (FOM) of the PEH under resonance condition, could not adequately explain the output performances of the 33-mode PEH with a specimen holder much larger than the size of the specimen. The d 33 × g 33 value, which is a FOM derived from the theoretical output power of the 33-mode PEH, can explain the variation of the output power of the 33-mode PEH with a large specimen holder. However, since the variation of the output power was more accurately explained by the d 33 × g 33 × value, this was suggested as a new FOM of the output power of the ring-type 33-mode PEH with a large specimen holder.

Rutile TiOlsubg2l/subg, a high temperature phase, has attracted interests as a capacitor dielectric in dynamic random access memories (DRAMs). Despite its high dielectric constant of g 80, large leakage currents caused by a low Schottky barrier height at the TiOlsubg2l/subg/electrode interface have hindered the use of rutile TiOlsubg2l/subg as a commercial DRAM capacitor. Here, we propose a new Ru-Pt alloy electrode to increase the height of the Schottky barrier. The Ru-Pt mixed layer was grown by atomic layer deposition. The atomic ratio of Ru/Pt varied in the entire range from 100 at.% Ru to 100 at.% Pt. Rutile TiOlsubg2l/subg films were inductively formed only on the Ru-Pt layer containing 43 at.% Pt, while anatase TiOlsubg2l/subg films with a relatively low dielectric constant (~ 40) were formed at Pt compositions g 63 at.%. The Ru-Pt (40 - 50 at.%) layer also attained an increase in work function of ~ 0.3 - 0.4 eV, leading to improvement in the leakage currents of the TiOlsubg2l/subg/Ru-Pt capacitor. These findings suggested that Ru-Pt layer could serve as a promising electrode for next-generation DRAM capacitors.

The solid solution system of 0.05Pb(Al.0.5Nb0.5)O3–0.95Pb(Zr0.52Ti0.48)O3 (PAN–PZT) has been studied for the piezoelectric ultrasonic motor with its high Tc. In this article, we doped the Nb2O5 and MnO2 into the 0.05PAN–0.95PZT ceramics as donor and acceptor respectively and reported the doping effect on the piezoelectric properties. Apparently, Nb2O5 induced the "soft" piezoelectric characteristics. However, as Nb2O5 also affected the sintered density, which is closely related with the piezoelectric properties, it is quite difficult to identify the role of Nb2O5, which might act as the "donor" and/or sintering enhancer. The optimized piezoelectric properties were obtained d33=430 pC/N, kp=59%, Qm=79, and e3T/e0=1690, when PAN–PZT+0.7 wt % Nb2O5 sintered at 1200 °C for 1 h. When MnO2 was doped, Mn4+ ions induced the distortion of perovskite structure and Tc shifted to lower temperature. In addition, d33 and kp decreased and Qm dramatically increased with the addition of MnO2. From these results, it was believed that MnO2 mainly acted as acceptor in PAN–PZT ceramics. The optimized piezoelectric properties were obtained d33=340 pC/N, kp=61.6%, Qm=1725, Tc=392 °C, and e3T/e0=1250, when PAN–PZT+0.7 wt % Nb2O5 with 0.5 wt % MnO2 ceramics sintered at 1200 °C for 1 h.

ZnO was added to 0.01Pb(Mg1/2W1/2)O3–0.41Pb(Ni1/3Nb2/3)O3–0.35PbTiO3–0.23PbZrO3 (0.01PMW–0.41PNN–0.35PT–0.23PZ) ceramics to reduce their sintering temperatures to below 900 °C. The effects of the ZnO additive on the densification and piezoelectric properties of the PMW–PNN–PT–PZ + 0.1 wt % Y2O3 + x wt % ZnO (0≤x≤2.5) ceramics were investigated. The structure of the PMW–PNN–PT–PZ ceramics was found to change from pseudocubic to tetragonal as their ZnO content was increased. The piezoelectric constant, the mechanical quality factor, and the electromechanical factor of the ceramics increased as their ZnO content increased. The optimum piezoelectric properties were found to be d33=594 pC/N, kp=57%, and Qm=64, for PMW–PNN–PT–PZ + 0.1 wt % Y2O3 + 1.5 wt % ZnO sintered at 900 °C for 2 h.

A modified structure for tiny ultrasonic linear motors has been developed, and various shaft materials have been tested in order to improve dynamic properties. The shaft material has a direct influence on efficiency, reliability, and quality of the motors and their dynamic properties. The shaft material is crucial to achieve high performance. Shafts of with various materials, such as a stainless steel, stainless steel coated with diamond like carbon (DLC), a Pyrex, and a graphite, can make it possible to improve dynamic properties of the motors over a wide range of tribological conditions. For the motor with a stainless steel shaft coated with DLC at 47 kHz, its velocity is 6.5 mm/s and its force is 110 mN. When the motor has a Pyrex shaft, a force of 140 mN is reached at 52 kHz. Accordingly, the maximum force produced by a motor with a graphite shaft is estimated as 97 mN. The velocity of this motor was 15 mm/s. We found that graphite has a fine surface and a directional texture which can help a moving element achieve linear motion. Finally, the use of a cap resulted in significantly improving stable operation. A motor with a graphite or a Pyrex shaft showed very stable operation and improved dynamic characteristics.

The controllability of the nucleation behavior of Pt in atomic layer deposition (ALD) by surface pretreatments with H2O, H2S, and NH3 was investigated. The H2O pretreatment on SiO2 and TiO2 surfaces had little effect on the nucleation of Pt. The H2S pretreatment on the SiO2 and TiO2 surfaces significantly delayed the nucleation of Pt on them, while the NH3 pretreatment on the TiO2 surface led to fluent nucleation of Pt. In particular, a continuous Pt film was successfully formed even at an ultrathin thickness of approximately 2.2 nm by NH3 pretreatment. This work suggests that the pretreatment with H2S and NH3 is an efficient way to control the nucleation of Pt in ALD without the support of any reactive species, such as plasma or O3. Such a strategy enables the easy control of the size and distribution density of Pt nanoparticles for a wide range of applications.

With the addition of TiO2, the dielectric constant (εr) of a Bi5Nb3O15(B5N3) film was slightly increased and the leakage current decreased, probably due to the increased dipole moment and the decreased number of free electrons in the film, respectively. The energy density of the laser beam considerably influenced the structure and electrical properties of the 1.0 mol% TiO2-doped B5N3 (TBN) films. At low beam energy densities (⩽2.0 J cm−2), Bi3NbO7 and Bi8Nb18O57 phases with a porous microstructure were formed and a poor interface was also formed between the film and the electrode. However, for the TBN film grown at 200 °C at a high beam energy density of 4.0 J cm−2, a dense Bi3NbO7 phase was formed with a sharp interface. The εr value of this TBN film was very high, approximately 115, with a low leakage current density of 1.4 × 10−8 A cm−2 at 0.5 MV cm−1 and a high breakdown field of 0.55 MV cm−1. This improvement in the εr value and the electrical properties was explained by the formation of a dense Bi3NbO7 phase with a (1 1 1) preferred orientation, Ti doping and a sharp interface, indicating that the TBN film is a good candidate material for embedded capacitors.

Amorphous Bi5Nb3O15 (B5N3) phase was formed for the films grown at 350 °C under low oxygen pressures (OPs) (≤200 mTorr). However, when OP exceeded 400 mTorr, crystalline Bi3NbO7 (B3N) phase, which is a low temperature transient phase of the crystalline B5N3 phase, was formed even at 350 °C. The dielectric constant (k) increased with increasing OP due to the formation of the crystalline B3N phase. The leakage current density increased with increasing OP, due to the increased surface roughness of the film. Presence of the intrinsic oxygen vacancies was also responsible for the increased leakage current density. Mn-doping improved the electrical properties of the films by producing the doubly ionized, extrinsic oxygen vacancies which reduced the number of the intrinsic oxygen vacancies. Mn-doping also considerably increased the k value of the film to a maximum of 108 for the 5.0 mol % Mn-doped film grown at 350 °C.

Bi5Nb3O15 (B5N3) thin films grown at temperatures above 500 °C developed a crystalline B5N3 phase that decomposed into a BiNbO4 phase in the film grown at 700 °C, probably due to Bi2O3 evaporation. The leakage current density of the B5N3 film grown at 200 °C under an oxygen pressure (OP) of 100 mTorr was high at approximately 6.3 × 10−7 A cm−2 at 0.2 MV cm−1, with a small breakdown field of 0.24 MV cm−1 due to the presence of intrinsic oxygen vacancies. The electrical properties of the B5N3 films improved with increasing OP during the growth but the dielectric constant (er) decreased. The Mn-doping also improved the electrical properties of the B5N3 films grown under low OP by producing doubly ionized oxygen vacancies, which decreased the number of the intrinsic oxygen vacancies. Furthermore, the Mn-doping increased the er value of the B5N3 film, confirming the effectiveness of such doping in improving both the electrical and the dielectric properties of the B5N3 film. In particular, the 5.0 mol% Mn-doped B5N3 film grown at 200 °C under an OP of 100 mTorr exhibited a low leakage current density of 7.9 × 10−8 A cm−2 at 0.2 MV cm−1 and a large breakdown field of 0.4 MV cm−1 with a high er of 64.

Ferroelectric materials, Barium strontium titanate (BST), have spontaneous polarization and high dielectric constant. Recently, there has been a strong interest in thin film BST, tunable dielectric materials for frequency agile RF and microwave device applications. 1,2) Many researchers have been studied for growing epitaxial ferroelectric thin films without strain on lattice mismatched substrates for tunable microwave devices. When the epi-layer of ferroelectric was grown on substrates, it is strained due to lattice mismatch. 3) Strain is a very significant factor in e!ect dielectric properties. The e!ect of the strain on the dielectric constant is due to the fact that ionic positions and vibrations in a ferroelectric are modified by the strain, and these changes are coupled to the polarization mechanism in the ferroelectric. 4) Sputtered BST films have been investigated by several researchers. 5‐7) The role of annealing process has been specifically studied for its influence on strain, and dielectric properties. 8) In this letter, we report an investigation of the e!ects of film strain on the dielectric properties of epitaxial BST films deposited by RF magnetron sputtering. Film strain in heteroepitaxial films can be cause by the mismatch between the lattice parameters and thermal expansion coe"cients of the ferroelectric film and substrate. The relationships between the strain and dielectric properties are discussed. Ba0:5Sr0:5TiO3 (BST) thin films were grown on (100)MgO single crystal substrates at 800 ! C for 2h in various Ar/O2 ratios by RF magnetron sputtering. The Ar and O2 flow rates were adjusted for a total pressure of 10mTorr. Typical deposition conditions of the BST thin films are shown in Table I. DC sputtering was applied for deposition of copper electrode on BST thin films. Copper electrode patterns were materialized by chemical etching. The crystal structure of the films was examined by X-ray di!raction (XRD) and reflection high energy electron di!raction (RHEED) measurements. Atomic force microscopy (AFM) was used to determine surface roughness. Compositional data were determined through Rutherford backscattering spectroscopy (RBS) analysis. The dielectric characteristics and tunability of the ferroelectric films were measured using a HP 4294A impedance analyzer at the 1MHz. The dielectric properties of BST films were extracted using a modified conformal

The microstructures and the microwave dielectric properties of Ca[(Li1/3Nb2/3)1-x Ti x ]O3-δ (CLNT) ceramics with different amount of glass frit additions were investigated. Addition of glass frit(B2O3–ZnO–SiO2–PbO system) improved the densification and decreased the sintering temperature from 1150°C to 900°C of Ca[(Li1/3Nb2/3)1-x Ti x ]O3-δ microwave dielectric ceramics. The dielectric constants (ε r) and bulk density were increased, as increasing glass contents from 10 wt% to 15 wt%. The quality factor (Q·f 0), however, was decreased slightly. The temperature coefficients of the resonant frequency (τf) shifted positive value as glass contents were increased. The dielectric properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3-δ with 12 wt% glass sintered at 900°C for 3 h were ε r=40, Q·f 0=12,500, τf=-8 ppm/°C, respectively. The relationship between the microstructure and dielectric properties of ceramics was studied by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM).

The microwave dielectric properties of (Pb0.4Ca0.6){(Mg1/3Nb2/3)1-x Sn x }O3 (0≤x≤0.1) ceramics have been investigated. The (Pb0.4Ca0.6)(Mg1/3Nb2/3)O3 ceramic was tetragonal complex perovskite single phase material and single phase specimens having tetragonal complex perovskite could also be obtained in case of substituting by tin(Sn). The partial substitution of [Mg1/3Nb2/3]4+ by Sn4+ at B-site of the perovskite structure significantly improves the loss quality factor (Q) and slightly decreases dielectric constant (ε r) and temperature coefficient of resonant frequency (τf). The temperature coefficient of resonant frequency of 0 ppm/°C was realized at x=0.01. The Q·f o value and ε r for this composition were found to be 7130 GHz and 64.7 respectively.