Enhanced Pyroelectric Performance of Lead-Free Zn-Doped Na1/2Bi1/2TiO3-BaTiO3 Ceramics

Lead-free Na1/2Bi1/2TiO3-BaTiO3 (NBT-BT) has gained revived interest due to its exceptionally good high power properties in comparison to commercial lead-based piezoelectrics. Recently, Zn-modified NBT-BT-based materials as solid solution and composites have been reported to exhibit enhanced depolarization temperatures and a high mechanical quality factor. In this work, the pyroelectric properties of Zn-doped NBT-6mole%BT and NBT-9mole%BT ceramics are investigated. The doped compositions of NBT-6BT and NBT-9BT feature a relatively stable pyroelectric property in a wide temperature range of ~37 K (300–330 K) and 80 K (300–380 K), respectively. A threefold increase in detector figure of merit is noted for 0.01 mole Zn-doped NBT-6mole% BT at room temperature in comparison to undoped NBT-6mole%BT and this increase is higher than those of major lead-free materials. A broad range of the temperature-independent behavior for the figures of merit was noted (303–380 K) for Zn-doped NBT-6mole% BT, which is 30 K higher than the undoped material. The large pyroelectric figures of merit and good temperature stability renders Zn-doped NBT-BT an ideal candidate for pyroelectric detector and energy harvesting applications.

Dependence of Modified Butterworth Van-Dyke Model Parameters and Magnetoimpedance on DC Magnetic Field for Magnetoelectric Composites

This study investigates the impedance curve of magnetoelectric (ME) composites (i.e., Fe80Si9B11/Pb(Zr0.3Ti0.7)O3 laminate) and extracts the modified Butterworth–Van Dyke (MBVD) model’s parameters at various direct current (DC) bias magnetic fields Hdc. It is interesting to find that both the magnetoimpedance and MBVD model’s parameters of ME composite depend on Hdc, which is primarily attributed to the dependence of FeSiB’s and neighboring PZT’s material properties on Hdc. On one hand, the delta E effect and magnetostriction of FeSiB result in the change in PZT’s dielectric permittivity, leading to the variation in impedance with Hdc. On the other hand, the magnetostriction and mechanical energy dissipation of FeSiB as a function of Hdc result in the field dependences of the MBVD model’s parameters and mechanical quality factor. Furthermore, the influences of piezoelectric and electrode materials properties on the MBVD model’s parameters are analyzed. This study plays a guiding role for ME sensor design and its application.

Influence of Quenching and Subsequent Annealing on the Conductivity and Electromechanical Properties of Na1/2Bi1/2TiO3-BaTiO3

Na1/2Bi1/2TiO3-based materials have gained considerable attention for their potential to exhibit giant strain, very-high ionic conductivity comparable to yttria stabilized zirconia or high mechanical quality factor for use in high power ultrasonics. In recent times, quenching Na1/2Bi1/2TiO3-based compositions have been demonstrated to enhance the thermal depolarization temperature, thus increasing the operational temperature limit of these materials in application. This work investigates the role of quenching-induced changes in the defect chemistry on the dielectric, ferroelectric and piezoelectric properties of quenched Na1/2Bi1/2TiO3-BaTiO3. The quenched samples indeed demonstrate an increase in the bulk conductivity. Nevertheless, while subsequent annealing of the quenched samples in air/oxygen atmosphere reverts back the depolarization behaviour to that of a furnace cooled specimen, the bulk conductivity remains majorly unaltered. This implies a weak correlation between the defect chemistry and enhanced thermal stability of the piezoelectric properties and hints towards other mechanisms at play. The minor role of oxygen vacancies is further reinforced by the negligible (10–15%) changes in the mechanical quality factor and hysteresis loss.

Influence of YTS addition on structural and electrical properties of PZT-based ceramics

Perovskite solid solution (1-x)Pb(Zr0.52Ti0.48)O3-xY(Ta1/2Sb1/2)O3 ceramics (abbreviated as PZT-YTS, where x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05) were synthesized by conventional solid state method. The phase structure, microstructure and corresponding electrical properties were studied. X-ray diffraction and Raman analyses show that tetragonal phase structure was obtained in all ceramics at room temperature. Scanning electron micrographs of the samples show uniform grain distribution and grain growth inhibition with the increase of doping content. The dielectric permittivity, dissipation factor, electromechanical coupling factor, Young modulus, mechanical quality factor, piezoelectric charge constant, actual density and piezoelectric voltage constant, for the ceramics with x = 0.04 were: ?r = 714.9, tan ? = 0.03345, KP = 0.635, Y = 10.528 ? 1010 N/m2, Qm = 622.254, d31 = 74.738 ? 10?12 C/N, ?a = 7.67 g/cm3 and g31 = 10.477 ? 10?3 m?V/N, respectively, which are optimal in comparison to other studied samples.

High Magnetic Field Sensitivity in Ferromagnetic–Ferroelectric Composite with High Mechanical Quality Factor

In this study, composite devices were fabricated using ferromagnetic FeSiB-based alloys (Metglas) and ferroelectric ceramics, and their magnetic field sensitivity was evaluated. Sintered 0.95Pb(Zr0.52Ti0.48)O3-0.05Pb(Mn1/3Sb2/3)O3 (PZT-PMS) ceramic exhibited a very dense microstructure with a large piezoelectric voltage coefficient (g31 = −16.8 × 10−3 VmN−1) and mechanical quality factor (Qm > 1600). Owing to these excellent electromechanical properties of the PZT-PMS, the laminate composite with a Metglas/PZT-PMS/Metglas sandwich structure exhibited large magnetoelectric voltage coefficients (αME) in both off-resonance and resonance modes. When the length-to-width aspect ratio (l/w) of the composite was controlled, αME slightly varied in the off-resonance mode, resulting in similar sensitivity values ranging from 129.9 to 146.81 VT−1. Whereas in the resonance mode, the composite with small l/w exhibited a large reduction of αME and sensitivity values. When controlling the thickness of the PZT-PMS (t), the αME of the composite showed the largest value when t was the smallest in the off-resonance mode, while αME was the largest when t is the largest in the resonance mode. The control of t slightly affected the sensitivity in the off-resonance mode, however, higher sensitivity was obtained as t increased in the resonance mode. The results demonstrate that the sensitivity, varying with the dimensional control of the composite, is related to the mechanical loss of the sensor. The composite sensor with the PZT-PMS layer exhibited excellent magnetic field sensitivity of 1.49 × 105 VT−1 with a sub-nT sensing limit, indicating its potential for application in high-performance magnetoelectric sensor devices.

Observation of nonlinear dynamics in an optical levitation system

Optical levitation of mechanical oscillators has been suggested as a promising way to decouple the environmental noise and increase the mechanical quality factor. Here, we investigate the dynamics of a free-standing mirror acting as the top reflector of a vertical optical cavity, designed as a testbed for a tripod cavity optical levitation setup. To reach the regime of levitation for a milligram-scale mirror, the optical intensity of the intracavity optical field approaches 3 MW cm−2. We identify three distinct optomechanical effects: excitation of acoustic vibrations, expansion due to photothermal absorption, and partial lift-off of the mirror due to radiation pressure force. These effects are intercoupled via the intracavity optical field and induce complex system dynamics inclusive of high-order sideband generation, optical bistability, parametric amplification, and the optical spring effect. We modify the response of the mirror with active feedback control to improve the overall stability of the system.

Microstructure and Piezoelectricity of (Na,K,Li)(Nb,Sb)O3–(Bi,Na)(Sr)ZrO3–BaZrO3 Ceramics

In this paper, (Na,K)1−xLi.x(Nb,Sb)O3–(Bi,Na)(Sr)ZrO3–BaZrO3 ceramics were fabricated with x(= Li) substitution by two-step sintering method, and their physical characteristics were investigated. When Li substitution was added to the ceramics, piezoelectric constant (d33) and electromechanical coupling factor (kp) were rapidly reduced. However, mechanical quality factor (Qm) was enhanced. For the KNN-BNZ((K,Na)(Nb)O3–(Bi,Na)(Sr)ZrO3) ceramics with Li(x) = 0 substitution, the best physical properties of d33 = 300 [pC/N], kp = 0.40, Qm = 33 and dialectic constant (εr) = 2430 were shown, respectively. Additionally, the KNN-BNZ ceramics with Li(x) = 0.02, the d33 of 246[pC/N], the kp of 0.37, the Qm of 42 and the εr of 2090 appeared, which were suitable for the low-loss piezoelectric actuator.