Piezoelectric Actuators and Motors: Materials, Designs, and Applications

It is well known that the piezoelectric performance of ferroelectric Pb(Zr,Ti)O3 (PZT) based ceramics is far inferior to that of ferroelectric single crystals due to ceramics' polycrystalline nature. Herein, it is reported that piezoelectric stress coefficient e33 = 39.24 C m−2 (induced electric displacement under applied strain) in the relaxor piezoelectric ceramic 0.55Pb(Ni1/3Nb2/3)O3–0.135PbZrO3–0.315PbTiO3 (PNN‐PZT) prepared by the solid state reaction method exhibits the highest value among various reported ferroelectric ceramic and single crystal materials. In addition, its piezoelectric coefficient d33* = 1753 pm V−1 is also comparable with that of the commercial Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) piezoelectric single crystal. The PNN‐PZT ceramic is then assembled into a cymbal energy harvester. Notably, its maximum output current at the acceleration of 3.5 g is 2.5 mApp, which is four times of the PMN‐PT single crystal due to the large piezoelectric e33 constants; while the maximum output power is 14.0 mW, which is almost the same as the PMN‐PT single crystal harvester. The theoretical analysis on force‐induced power output is also presented, which indicates PNN‐PZT ceramic has great potential for energy device application.

Giant Piezoelectric Coefficients in Relaxor Piezoelectric Ceramic PNN-PZT for Vibration Energy Harvesting

In order to obtain BNT-based ceramic system with excellent electric-field-induced strain performance for actuator applications, a novel solid solution (100-x)Bi1/2(Na0.82K0.12)1/2TiO3-xBi4Ti3O12 ((100-x)BNKT-xBiT, x = 0–12 wt%) was designed and fabricated by solid state synthesis. The microstructure and related electrical properties of this material were systematically investigated. It was found that BiT is dissolved into the lattice structure of the BNKT, leading to a greater increase in the volatilization of Na and K, thus produce more A-site vacancies compared with the undoped BNKT. The 9 wt%BiT doped sample not only has sufficient A-site vacancies to destroy the long-range ferroelectric order of the base composition but also favors the presence of extremely stable relaxor phase at room temperature. Further, the ferroelectric-to-relaxor phase transition temperature TF-R can be effectively tuned to about 0 °C, giving rise to a large signal piezoelectric coefficient d*33 of 485 pm/V with a small hysteresis η of 23%.

Large strain with low hysteresis in Bi4Ti3O12 modified Bi1/2(Na0.82K0.18)1/2TiO3 lead-free piezoceramics

Giant piezoelectric coefficient of PNN-PZT-based relaxor piezoelectric ceramics by constructing an R-T MPB

In this study, novel magnetic mesoporous Fe3O4@mSiO2–DODGA nanoparticles were prepared for efficiently adsorbing and recycling REEs. Fe3O4@mSiO2–DODGA was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The adsorption behavior of Fe3O4@mSiO2–DODGA was investigated by ICP-OES. The results showed that the content of DODGA in the adsorbent was 367 μmol g−1. Fe3O4@mSiO2–DODGA exhibited the highest adsorption rates for 15 REEs, except Tm, in a 2 mol L−1 nitric acid solution. Among these elements, the adsorption rates for Nd, Sm, Eu, Dy, Ho, Yb, Lu, Y and Sc ranged from 85.1% to 100.1%. The desorption rates for all 16 REE ions reached their maximum values when 0.01 mol L−1 EDTA was used as the eluent. The desorption rates for Nd, Ce, Sm, Eu, Ho, Yb, Lu, Y, and Sc were 87.7–99.8%. Fe3O4@mSiO2–DODGA had high stability in 2 mol L−1 HNO3 and could be used five times without significant loss of adsorption capacity. Moreover, these nanoparticles had high selectivity, and their adsorption rate was not affected even in a high-concentration solution of a coexisting ion. Therefore, 8 REE ions (Nd, Sm, Eu, Ho, Yb, Lu, Y, and Sc) were selected for the study of adsorption kinetics and adsorption isotherm experiments. It was demonstrated that the values of Qe (equilibrium adsorption capacity) for Nd, Sm, Eu, Ho, Yb, Lu, Y, and Sc were 14.28–60.80 mg g−1. The adsorption of REEs on Fe3O4@mSiO2–DODGA followed the pseudo-second-order kinetic model, Elovich model and Langmuir isotherm model, which indicated that the adsorption process of Fe3O4@mSiO2–DODGA for REEs comprised single-layer adsorption on a non-uniform surface controlled by chemical adsorption. It was concluded that Fe3O4@mSiO2–DODGA represents a new material for the adsorption of REEs in strongly acidic solutions.

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Synthesis and characterization of magnetic mesoporous Fe3O4@mSiO2–DODGA nanoparticles for adsorption of 16 rare earth elements

Pb(Zn1/3Ni2/3)c(Ni1/3Nb2/3)a(ZrxTiy)bO3 (PZN–PNN–PZT, the ratios of PNN/PZT a/b were 0.88, 1 and 1.136) piezoelectric ceramics were prepared by a traditional solid-state reaction method. The effects of PNN/PZT ratio on phase structure, microstructure and electric properties as well as the relaxation behaviors of PZN–PNN–PZT ceramics were investigated. The XRD patterns showed that all ceramics samples had a pure perovskite phase structure. Meanwhile, it was found that the phase structure undergoes a tetragonal, tetragonal-rhombohedral to rhombohedral transition as ratios of PNN/PZT increased. With the increasing of a/b from 0.88 to 1.136, the dielectric constant and diffusive phase coefficient decreases, it was indicated that relaxation behaviors also decreased. When ceramics with a/b was 1.136, the dielectric relaxation γ reached the minimum and electrical properties were poor. The electric properties of ceramics with a/b was 1.00 have an excellent properties, it was indicated that ceramics reached an optimization at the MPB structure.

Effects of PNN/PZT ratios on phase structure, electric properties and relaxation behavior of PZN–PNN–PZT ceramics

The incorporation of noncanonical amino acids (ncAAs) into fluorescent proteins is promising for red-shifting their fluorescence and benefiting tissue imaging with deep penetration and low phototoxicity. However, ncAA-based red fluorescent proteins (RFPs) have been rare. The 3-aminotyrosine modified superfolder green fluorescent protein (aY-sfGFP) represents a recent advance, yet the molecular mechanism for its red-shifted fluorescence remains elusive while its dim fluorescence hinders applications. Herein, we implement femtosecond stimulated Raman spectroscopy to obtain structural fingerprints in the electronic ground state and reveal that aY-sfGFP possesses a GFP-like instead of RFP-like chromophore. Red color of aY-sfGFP intrinsically arises from a unique "double-donor" chromophore structure that raises ground-state energy and enhances charge transfer, notably differing from the conventional conjugation mechanism. We further developed two aY-sfGFP mutants (E222H and T203H) with significantly improved (∼12-fold higher) brightness by rationally restraining the chromophore's nonradiative decay through electronic and steric effects, aided by solvatochromic and fluorogenic studies of the model chromophore in solution. This study thus provides functional mechanisms and generalizable insights into ncAA-RFPs with an efficient route for engineering redder and brighter fluorescent proteins.

Structural origin and rational development of bright red noncanonical variants of green fluorescent protein.

The structure, microstructure, field-induced strain, ferroelectric, piezoelectric and dielectric properties of (1 − x) (Bi0.5Na0.5)0.935Ba0.065TiO3–xSr3CuNb2O9 (BNT-BT6.5–xSCN, with x = 0, 0.003, 0.006, 0.009) ceramics were investigated. X-ray diffraction patterns show that all samples are pure perovskite structure and Sr3CuNb2O9 (SCN) effectively diffused into the 0.935Bi0.5Na0.5TiO3–0.065BaTiO3 (BNT–BT6.5) solid solution which also reflected in the Raman spectra and the energy disperse spectroscopy (EDS) analysis. With the increases of SCN content, the coercive field (E
 c
  = 18.41 kV/cm) decreases greatly, whereas the remnant polarization (P
 r
  = 29.11 μC/cm2) increases a little at x = 0.003 which is showed in the polarization hysteresis (P–E) loops, the result indicate that the ferroelectric order would be disrupted. Around critical composition (x = 0.003) at a driving field of 60 kV/cm, a large unipolar strain of 0.29 % with a normalized strain (d
 33
  = 483 pm/V) is obtained at room temperature. The results indicate that BNT-BT6.5-xSCN ceramics with excellent properties are promising to replace lead-based piezoelectric ceramics and can be used in practical applications.

Structural and electrical properties of Bi1/2Na1/2TiO3-BaTiO3-Sr3CuNb2O9 lead-free piezoelectric ceramics

The present study is an investigation of the effects of Sm2O3 doping on properties near morphotropic phase boundary (MPB) of nickel niobium ternary system lead zirconate titanate (PNN–PZT) ceramics. Pb(Ni1/3Nb2/3)0.5 (Zr0.3Ti0.7)0.5O3 (0.5PNN–0.5PZT + xSm) piezoelectric ceramics were prepared by a traditional two-step solid-state reaction method. The specimens exhibit the homogeneous perovskite structure without the secondary phase. When x = 0.6 wt% and x = 0.8 wt%, their diffraction peaks are the most obvious, they may have the best P–T MPB composition. The samples exhibit the P–T MPB composition have a good properties, which is in accord with the electric properties variation and the crystalline grain variation well. When x = 0.6 wt%, the ceramics exhibited electric properties: d33 = 688 pC/N, kp = 0.579, er = 6260, tanδ = 0.0207. It shows that the P–T MPB composition have relationships with the electric properties variation and the crystalline grain variation to some extent.

The effects of Sm2O3 doping on properties of PNN-PZT ceramics near morphotropic phase boundary

Prelinguallydeafened Mandarin-speaking children with cochlear implants (CI) encounter a significant challenge in perceiving lexical tones accurately due to their limited language experience and insufficient pitch information provided by CI devices. To facilitate their tonal perception, we examined the role of pitch gestures in the training program, which was reported to be beneficial in acquiring Mandarin lexical tones for foreign learners of Chinese. In the current study, 18 prelingually deafened preschoolers with CI were recruited in Shanghai. They were randomly assigned to two groups. The experimental group was trained with audio and pitch gestures, and the control group was trained with audio only. Three tone-identification tests were conducted before, in the middle, and after the eight training sessions. Although the two groups had identical performance before the training, the experimental group demonstrated significantly better performance than the control group after training sessions, especially in noise conditions. The results thus showed that multimodal training with pitch gestures improved the tone recognition ability of CI children more than sheer auditory training. Our findings offer more evidence to support that learning to perceive lexical tones can be facilitated by multimodal cues and also provide important implications for optimizing rehabilitation training after implantation.

Multimodal training using pitch gesture improves Mandarin tone recognition for children with cochlear implant

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