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To achieve compact and lightweight power conversion devices, magnetic core materials such as MnZn ferrite are highly desired with low core losses at high frequencies above megahertz. In this work, high-valent Sn4+ ions were doped into MnZn ferrite to manipulate the electromagnetic properties and suppress the high-frequency core losses. The distribution of Sn4+ in MnZn ferrite was investigated by transmission electron microscopy with energy dispersive x-ray analysis, which indicated that most of the substituted Sn4+ ions remained at the grain boundaries rather than dissolving into the lattice, and thus greatly impacted the electromagnetic properties of MnZn ferrite. The initial permeability and saturation induction decreased monotonically with the Sn substitution. The core loss was reduced to 457 kW m−3 at 3 MHz, 30 mT, and 25 °C when the Sn substitution content was 0.003, due to the effective suppression of eddy current loss and residual loss. The sample with a Sn content of 0.003 exhibited excellent overall electromagnetic properties, which could be potentially useful in high-frequency transformers, converters, and power sources.

Reducing the secondary electron yield (SEY) of Ag-plated aluminum alloy is important for high-power microwave components. In this work, Cu doped carbon films are prepared and the secondary electron emission characteristics are studied systematically. The secondary electron coefficient δ max of carbon films increases with the Cu contents increasing at first, and then decreases to 1.53 at a high doping ratio of 0.645. From the viewpoint of surface structure, the higher the content of Cu is, the rougher the surface is, since more cluster particles appear on the surface due to the small solid solubility of Cu in the amorphous carbon network. However, from viewpoint of the electronic structure, the reduction of the sp2 hybrid bonds will increase the SEY effect as the content of Cu increases, due to the decreasing probability of collision with free electrons. Thus, the two mechanisms would compete and coexist to affect the SEY characteristics in Cu doped carbon films.

The rapid development of the internet of things technology has led to great demand for intelligent electric field sensor (EFS). Several working principles have been proposed, however major challenges remain existed for the requirements of EFS with low-cost, large-range, and high-resolution. In this paper, an EFS based on piezoelectric (PE) bending effect using d 31 mode is developed, where a bending strain is induced on the sandwiched bimorph structure of PZT/PDMS/PZT under an applied electric field, and the capacitance value of the PDMS layer reveals detectable variation. We demonstrate an EFS operating at the stress-mediated coupling between PE ceramic and elastic dielectric polymer, which reveals advantages such as simple fabrication process, low-cost and low power consumption. Due to the sandwiched bimorph structure, the strain caused by the electric field can be effectively transferred to improve the resolution of the device. The constitutive equations for the sandwiched bimorph structure are built, and the working principle of the proposed EFS is demonstrated. The EFS exhibits high sensitivity under both AC and DC electric fields, with a resolution of 0.1 V cm−1 in the range of −3 to 3 kV cm−1. The proposed sensor provides an alternative solution for power equipment fault diagnosis, power frequency electric field detection, etc.

Voltage-tunable RF/microwave devices attract great attention due to their low power consumption; however, they still suffer from the fundamental dilemma between large tunability and low insertion loss. In this paper, yttrium iron garnet (YIG) polycrystalline thin films with low microwave loss (−4) were directly deposited on mica substrates via a van der Waals force and then transferred onto PMN-PT substrates. The in-plane magnetic anisotropy of YIG was tuned by the in-plane biaxial stress of PMN-PT, and an improved voltage tunability (175 MHz) of in-plane FMR fr was obtained due to the removal of the substrate clamping effect. Moreover, our samples still represent good frequency stability (4–12 GHz) during the tuning process. It is of significance for exploiting novel, portable, low-loss RF/microwave devices in the future.

Ceramic thin films with high dielectric constant and high breakdown strength hold special promise for advanced electronics applications. We deposited lanthanum-doped lead zirconate titanate (PLZT) on base metal foils (film-on-foils) by chemical solution deposition. The PLZT film-on-foils were characterized over a wide temperature range between room temperature and 200°C. For ≈2-μm-thick PLZT films grown on LaNO3-buffered nickel foils at room temperature, we measured a dielectric constant of ≈1300, dielectric loss of ≈0.07, remanent polarization of ≈26 μC/cm2, coercive field of ≈29 kV/cm, leakage current density of ≈9.2 × 10−9 A/cm2, and energy density of ≈67 J/cm3. Dielectric breakdown strength was determined to be ≈2.6 × 106 V/cm by Weibull analysis. These and other results reported here indicate that electronic devices with film-on-foil capacitors would possess higher performance, improved reliability, and enhanced volumetric and gravimetric efficiencies compared with traditional dielectric capacitors.

This paper reports the bipolar resistive switching (RS) effect of the Nd0.05Bi0.95FeO3/Nb:SrTiO3 heterostructure fabricated by pulsed laser deposition. This heterostructure shows a high RS ratio of over 600 at a read voltage of −0.3V after applying 5V/−8V pulse voltages. Moreover, the resistance states could be switched reversibly among multilevel resistance states by changing the magnitude of set or reset pulse voltages, which shows promise for multilevel nonvolatile memory application. The mechanism of the RS between high- and low-resistance states could be attributed to the carrier injection-trapped/detrapped process, which changes the height and thickness of the barrier at the Nd0.05Bi0.95FeO3/Nb:SrTiO3interface.

We deposited ferroelectric (Pb0.92La0.08)(Zr0.52Ti0.48)O3 films of ≈0.35 to ≈3.1 μm in thickness on platinized silicon substrates by chemical solution deposition. A dielectric constant of ≈1350 and dielectric loss of ≈0.04 were measured at room temperature. Hysteresis loop tests revealed that the remanent polarization increases while the coercive field decreases with PLZT film thickness. The residual stress in the PLZT films, as determined by the x-ray diffraction sin2ψ method, decreased from ≈380 to ≈200 MPa when the film thickness increased from 0.35 to 3.1 μm. The dependence of the residual stress (σ) on the PLZT film thickness (t) can be described by an empirical equation, σ = A0exp(−t2/λ2), with A0 ≈ 390 MPa and λ ≈ 3.8 μm.

This paper reports the resistive switching effects of ZnO, CeO2 and CeO2/ZnO stacked heterostructure deposited on Nb:SrTiO3 substrates by pulsed laser deposition. The CeO2/ZnO stacked heterostructure shows high resistive switching ratio of over 104 at a read voltage of −0.5 V and an expected retention ability of ten years, which is better than that of ZnO- or CeO2-based device. Furthermore, multilevel resistance states could be adjusted by changing the maximum value of the applied voltage, which shows promise for high-performance nonvolatile multilevel memory application. Studies indicated that the trap-mediated space charge limited conduction governs the low- and high-resistance states. The good resistive switching characteristics of CeO2/ZnO stacked heterostructure could be attributed to the carrier injection-trapped/detrapped process at the CeO2/ZnO interface and ZnO films in which oxygen vacancies act as ‘trapping center’.

Hard piezoelectric ceramics of manganese (Mn)-modified 0.36BiScO3–0.64PbTiO3 (0.36BS–0.64PTM) with a high Curie temperature were prepared using the traditional solid-state reaction method. The effects of different concentrations of Mn on the structure, dielectric and piezoelectric properties of the 0.36BS–0.64PTM ceramics were investigated. X-ray diffraction results indicated that the 0.36BS–0.64PTM ceramics showed a single perovskite structure with tetragonal symmetry and the c/a ratio decreased slightly with increasing Mn content. The grain sizes of the 0.36BS–0.64PTM ceramics were enlarged by Mn addition, and their distributions were uniform. The dielectric loss tan δ decreased clearly with the increase in Mn content, and the mechanical quality factor Q m and vibration velocity v 0 were improved significantly at the same time. The Curie temperature T c, the planar electromechanical coupling factor k p, dielectric loss tan δ, mechanical quality factor Q m and vibration velocity v 0 of the 0.36BS–0.64PTM ceramics with 3 mol% Mn were about 431 °C, 0.57, 0.007, 134 and 1.05 m s−1, respectively. The maximum vibration velocity v 0 of the 0.36BS–0.64PTM ceramics is much superior to those of PZT (0.4 m s−1) ceramics and PZT–PZM (0.72 m s−1). These results indicated that the 0.36BS–0.64PTM ceramics are promising candidates for high-temperature and high-power piezoelectric applications.

A TiO2 thin film was deposited on a Nb : SrTiO3 substrate by pulsed laser deposition to form an Ag/TiO2/Nb : SrTiO3/In device. The bipolar resistive switching (RS) effect of this device was investigated. The current–voltage characteristics exhibited pronounced and stable bipolar RS features. The device could be switched to a low resistance state (LRS) at forward voltage and returned to a high resistance state (HRS) at reverse voltage, and the RS ratio R HRS/R LRS reached up to 2 × 103 at a read voltage of −0.5 V. Moreover, the RS ratio could be adjusted by changing the maximum value of the forward or reverse voltage, which shows promise for multilevel memories. These results are discussed by considering carrier injection-trapped/detrapped process of the heterostructure and show high potential for nonvolatile memory applications.

Pure BiFeO3 (BFO), Nd-doped BFO (BNF) and Nd and Mo co-doped BFO (BNFM) multiferroic thin films were prepared by pulsed laser deposition on Pt/Ti/SiO2/Si substrates. Among these films, the BNFM film exhibited the lowest dielectric loss and leakage current density, a well-saturated P–E loop, excellent charge-retaining ability and fatigue-free behaviour. Furthermore, improved ferromagnetism was observed in this film with a saturation magnetization of ~15 emu cm−3. These significant improvements in ferroelectric and ferromagnetic properties could be preliminarily attributed to the elimination of oxygen vacancies and the increase in the Fe2+ ions in the film by Nd and high-valence Mo co-doping, respectively.