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Recently, memristors have garnered widespread attention as neuromorphic devices that can simulate synaptic behavior, holding promise for future commercial applications in neuromorphic computing. In this paper, we present a memristor with an Au/Bi3.2La0.8Ti3O12(BLTO)/ITO structure, demonstrating a switching ratio of nearly 103over a duration of 104 s. It successfully simulates a range of synaptic behaviors, including long-term potentiation and depression, paired-pulse facilitation, spike-timing-dependent plasticity, spike-rate-dependent plasticity etc. Interestingly, we also employ it to simulate pain threshold, sensitization, and desensitization behaviors of pain-perceptual nociceptor (PPN). Lastly, by introducing memristor differential pairs (1T1R-1T1R), we train a neural network, effectively simplifying the learning process, reducing training time, and achieving a handwriting digit recognition accuracy of up to 97.19 %. Overall, the proposed device holds immense potential in the field of neuromorphic computing, offering possibilities for the next generation of high-performance neuromorphic computing chips.

Metal–organic frameworks (MOFs) have attained broad research attention in the areas of sensors, resistive memories, and optoelectronic synapses on the merits of their intriguing physical and chemical properties. In this review, recent progress on the synthesis of MOFs and their electronic applications is introduced and discussed. Initially, the crystal structures and properties of MOFs encompassing optical, electrical, and chemical properties are discussed in brief. Subsequently, advanced synthesis methods for MOFs are introduced, categorized into hydrothermal approach, microwave synthesis, mechanochemical synthesis, and electrochemical deposition. After that, the various roles of MOFs in widespread applications, including sensing, information storage, optoelectronic synapses, machine learning, and artificial intelligence, are discussed, highlighting their versatility and the innovative solutions they provide to long-standing challenges. Finally, an outlook on remaining challenges and a future perspective for MOFs are proposed.

Today’s computing systems, to meet the enormous demands of information processing, have driven the development of brain-inspired neuromorphic systems. However, there are relatively few optoelectronic devices in most brain-inspired neuromorphic systems that can simultaneously regulate the conductivity through both optical and electrical signals. In this work, the Au/MXene/Y:HfO2/FTO ferroelectric memristor as an optoelectronic artificial synaptic device exhibited both digital and analog resistance switching (RS) behaviors under different voltages with a good switching ratio (>103). Under optoelectronic conditions, optimal weight update parameters and an enhanced algorithm achieved 97.1% recognition accuracy in convolutional neural networks. A new logic gate circuit specifically designed for optoelectronic inputs was established. Furthermore, the device integrates the impact of relative humidity to develop an innovative three-person voting mechanism with a veto power. These results provide a feasible approach for integrating optoelectronic artificial synapses with logic-based computing devices.

The research found that after doping with rare earth elements, a large number of electrons and holes will be produced on the surface of AlN, which makes the material have the characteristics of spontaneous polarization. A new type of ferroelectric material has made a new breakthrough in the application of nitride-materials in the field of integrated devices. In this paper, the application prospects and development trends of ferroelectric material ScAlN in memristors are reviewed. Firstly, various fabrication processes and structures of the current ScAlN thin films are described in detail to explore the implementation of their applications in synaptic devices. Secondly, a series of electrical properties of ScAlN films, such as the current switching ratio and long-term cycle durability, were tested to explore whether their electrical properties could meet the basic needs of memristor device materials. Finally, a series of summaries on the current research studies of ScAlN thin films in the synaptic simulation are made, and the working state of ScAlN thin films as a synaptic device is observed. The results show that the ScAlN ferroelectric material has high residual polarization, no wake-up function, excellent stability and obvious STDP behavior, which indicates that the modified material has wide application prospects in the research and development of memristors.

Neuromorphic computing, which mimics biological neural networks, is widely regarded as the optimal solution for addressing the limitations of traditional von Neumann computing architecture. In this work, an adjustable multistage resistance switching ferroelectric Bi2FeCrO6diode artificial synaptic device was fabricated using a sol–gel method with a simple process. The device exhibits nonlinearity in its electrical characteristics, demonstrating tunable multistage resistance switching behavior and a strong ferroelectric diode effect through the manipulation of ferroelectric polarization. One of its salient advantages resides in its capacity to dynamically regulate its polarization state in response to an external electric field, thereby facilitating the fine-tuning of synaptic connection strength while maintaining synaptic stability. The device is capable of accurately simulating the fundamental properties of biological synapses, including long/short-term plasticity, paired-pulse facilitation, and spike-timing-dependent plasticity. Additionally, the device exhibits a distinctive photoelectric response and is capable of inducing synaptic plasticity by light signal activation. The utilization of a femtosecond laser for the scrutiny of carrier transport mechanisms imparts profound insights into the intricate dynamics governing the optical memory effect. Furthermore, utilizing a convolutional neural network (CNN) architecture, the recognition accuracy of the MNIST and fashion MNIST datasets was improved to 95.6% and 78%, respectively, through the implementation of improved random adaptive algorithms. These findings present a new opportunity for utilizing Bi2FeCrO6materials in the development of artificial synapses for neuromorphic computation.

BaTiO3(BT) has attracted extensive attention among advanced lead-free ferroelectric materials due to its unique dielectric and ferroelectric properties. However, the enormous remanent polarization and coercive field severely impede the improvement of its energy storage capabilities. Here, the BaTiO3Bi(Zn0.5Hf0.5)O3(BT-BZH) ceramics with high breakdown field strength and remarkable relaxation characteristics can be obtained by introducing the composite component BZH in BT to regulate the phase structure and grain size of the ceramics. The findings demonstrate that the improvement of energy storage performance is related to the increase of relaxation behavior. A large energy storage density (Wrec∼3.62 J/cm3) along with superior energy storage efficiency (η∼88.5%) is achieved in 0.88BT-0.12BZH relaxor ceramics only at 240 kV/cm. In addition, the sample suggests superior thermal stability and frequency stability within 25–115 °C and 1–500 Hz, respectively. Furthermore, the outstanding charge-discharge properties with an ultrafast discharge time (100 ns), large discharged energy density (1.2 J/cm3), impressive current density (519.4 A/cm2) and power density (31.1 MW/cm3) under the electric field of 120 kV/cm are achieved in studied ceramics. The excellent energy storage performance of BT-BZH ceramics provides a promising platform for the application of lead-free energy-storage materials.

In the case of dielectric energy storage devices, excessive pursuit of giant electric fields means greater exposure to high temperatures and insulation damage risk. Ferroelectric thin film devices offer opportunities for energy storage needs under finite electric fields due to their intrinsically large polarization and the advantage of small size. Herein, we designed the capacitor’s dielectric layer by doping barium titanate Ba(1-x)CexTiO3 (BCTO). The addition of highly charged ions Ce3+ induce cell shrinkage thus further optimizing the ferroelectric polarization. Accordingly, the capacitor with Au/BCTO/Au structure integrated directly on silicon substrate showed excellent energy storage performance ( ${W} _{\text {rec}}~\approx ~92.6$ J/cm3 and $\eta ~\approx ~86.5$ %) under only 1961 kV/cm. In addition, we significantly increased the electrical breakdown strength from 1726 kV/cm to 3426 kV/cm by adjusting the Ba0.95Ce0.05TiO3 film thickness, thus achieving ultra-high energy storage density (107.9 J/cm3). The results expand the application prospects of silicon-based ferroelectric capacitors for energy storage at low electric field strength.

Triboelectric sensing technology reinforced with deep learning algorithm has shown significant potentials in the fields of sophisticated wearable devices and Internet of Things (IoT) applications. Herein, we present a large-scale and printable nanocomposite film for high-performance microstructured BaTiO3/Ecoflex triboelectric nanogenerator (MBE-TENG) and demonstrate its applications in deep-learning assisted self-powered sensing and human-machine interaction. The MBE-TENG device achieves a short-circuit current of 1.46 μA, an open-circuit voltage of 144 V, and a transfer charge density of 6.62 nC/cm². Additionally, the MBE-TENG device can charge a 10 μF capacitor from 0 to 2 V within 200 seconds, illuminate over 70 commercial LEDs, and power a digital calculator. Based on the MBE-TENG, a sensory array keyboard is demonstrated to wirelessly control the movement of a smart car via Bluetooth communication. Furthermore, a smart tactile sensing glove is developed by combining the MEB-TENG, residual neural network and convolutional block attention module, realizing the facile recognition on six different objects with a high accuracy of 96.33 %. This work presents a scalable fabrication for microstructured triboelectric layer and highlights the versatility and efficiency of TENG sensing technology when combined with advanced neural networks and embedded systems, paving the way for innovative development in human-machine interaction, personalized healthcare, and intelligent control interfaces.

0.7Bi(1−x)NdxFeO3–0.3BaTiO3(BNFO–BTO, x=0.005, 0.010, 0.020 and 0.050) ceramics were fabricated using the high-temperature solid-state reaction method. The X-ray diffraction (XRD) patterns revealed that the primary phase in these ceramics was pseudocubic. The Scanning Electron Microscopy (SEM) micrographs exhibited dense microstructures throughout all BNFO–BTO ceramics. Furthermore, the temperature dependence of dielectric behaviors and ferroelectric hysteresis loop shapes suggested the occurrence of a relaxor ferroelectric-type phase transition in BNFO–BTO ceramics. Additionally, the frequency dispersion characteristics and remnant polarization were enhanced with increasing substitution of Bi3+by Nd3+. Conducted impedance analysis on 0.7Bi(1−x)NdxFeO3–0.3BaTiO3ceramics and two dielectric responses of the grain at high frequency and grain boundary at low frequency were illustrated, respectively. The combination of imaginary impedance (Z″)and imaginary modulus (M″)versus logfplots revealed that the charge carriers’ motion was not entirely long-range, short-range migration also exists. Through calculations based on Curie–Weiss Law, the relaxation activation energy (Ea)and conductance activation energy (Ec)were investigated, confirming that doping Nd3+effectively mitigates the concentration of oxygen vacancies (OVs) and prevents the formation of oxygen vacancies clusters, ultimately suppressing conductivity in BNFO–BTO ceramics.

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Extremely high temperature in a chip will severely affect the normal operation of electronic equipment; however, the traditional air conditioning cooling technology is unsuitable for integrated circuit cooling. It is necessary to develop convenient and high-efficiency cooling techniques. In this paper, PbHfO3antiferroelectric (PHO AFE) film was fabricated by a sol–gel method and was first found to be a promising electrocaloric (EC) material with high temperature change (ΔT∼ −7.7 K) and acceptable EC strength (|ΔT/ΔE| ∼ 0.023 K cm kV–1) at room temperature. In addition to the negative EC effect (ECE), a large positive ECE can be observed at high temperature. The outstanding ECEs and their combination will make the PHO film one of the potential candidates for next-generation solid-state refrigeration. To understand the underlying physical mechanism for positive and negative ECEs in the PHO AFE film, a modified Ginzburg–Landau–Devonshire free-energy theory is adopted.

As an important method to further improve the storage density of resistive memory, multistage resistive switching devices have become an important research direction. However, no stable and controllable multistage resistive switching device has been prepared, and the working mechanism is still unclear. Here, a sandwich-structured device is simply prepared by spin coating, with the work layer is the Bi2FeCrO6thin film. The device can realize bidirectional controllable multistage resistive switching behavior, the biggest on/off ratio is 104, and it can maintain stability without attenuation at 100 times slow loop and 104times pulse cycle. The analyzes showed that the charged ions formed by defects in the device migrated under the action of an external electric field lead to the Schottky barrier height reversible changed. Which is the key to cause multistage resistive switching behavior. This work is the first report about the voltage control of bidirectional adjustable multistage resistive switching behavior in the Bi2FeCrO6thin film. The principle of generation is analyzed, and important ideas and insights are provided for the preparation and treatment of related multistage resistive problems.

PbxSr1-xTiO3(x = 0.30, 0.35, 0.40, 0.45, 0.50 and 0.55) ceramics were fabricated by a solid-state reaction route. X–ray diffraction data at room temperature show PST samples shift from cubic to tetragonal phase with the increase of Pb2+content. The microstructures were observed by scanning electron microscopy. Dielectric measurement was employed to investigate the ferroelectric–paraelectric phase transition behavior. Temperature dependent polarization–electric field hysteresis loops were conducted to study the electrocaloric effect (ECE) of the ferroelectric ceramics by indirect methods over a wide temperature range. Direct measurement of temperature change (ΔT) at room temperature for all samples can achieve 0.79–1.86 K. What's more, a giant ECE (ΔT = 2.05 K, EC strength (ΔT/ΔE) = 0.51 × 10−6 K m/V, under 40 kV/cm) was obtained in the sample of x = 0.35 near phase transition temperature. Our results suggest that the ceramics are promising cooling materials with excellent EC properties for energy related applications.

High-entropy materials (HEMs) have recently emerged as a prominent research focus in materials science, gaining considerable attention because of their complex composition and exceptional properties. These materials typically comprise five or more elements mixed approximately in equal atomic ratios. The resultant high-entropy effects, lattice distortions, slow diffusion, and cocktail effects contribute to their unique physical, chemical, and optical properties. This study reviews the electrical, magnetic, and optical properties of HEMs and explores their potential applications. Additionally, it discusses the theoretical calculation methods and preparation techniques for HEMs, thereby offering insights and prospects for their future development.

The conventional von Neumann architecture has proven to be inadequate in keeping up with the rapid progress in artificial intelligence. Memristors have become the favored devices for simulating synaptic behavior and enabling neuromorphic computations to address challenges. An artificial synapse utilizing the perovskite structure PbHfO3(PHO) has been created to tackle these concerns. By employing the sol–gel technique, a ferroelectric film composed of Au/PHO/FTO was created on FTO/glass for the purpose of this endeavor. The artificial synapse is composed of Au/PHO/FTO and exhibits learning and memory characteristics that are similar to those observed in biological neurons. The recognition accuracy for both MNIST and Fashion-MNIST data sets saw an increase, reaching 92.93% and 76.75%, respectively. This enhancement resulted from employing a convolutional neural network architecture and implementing an improved stochastic adaptive algorithm. The presented findings showcase a viable approach to achieve neuromorphic computation by employing artificial synapses fabricated with PHO.

Lead-free ferroelectric ceramics (1-x) BaTiO3–xBi(Mg1/2Ti1/2)O3(x = 0.0–0.07) were synthesized by conventional solid state reaction method and the correlation of structure, dielectric, ferroelectric and impedance properties were investigated. It was found that Tmand εmshowed decreasing trend with the increase of BMT content. The high-temperature dielectric relaxation behaviour was observed in all the samples. The activation energy calculated from impedance (Ea) and conductivity (Econd), which revealed that the relaxation behaviours were linked with the migration of OVs. The values of Eawere almost equivalent to Econd. It was concluded that the short-range hopping of oxygen vacancy contributed to the dielectric relaxation and long-distance movement of doubly ionized oxygen vacancies contributed to the conduction. On the other hand, with increasing BMT contents, it was found that P-Eloops became slimmer and slimmer, which indicated the increase of relaxor behaviour. The temperature dependence of P-Eloops for 0.98BT–0.02BMT ceramic clearly showed the transition process from ferroelectric to relaxed ferroelectrics.

The widely used pesticide thiram is found in various environments and foodstuffs, posing a risk to human health and contaminating the environment. In this work, the novel SERS flexible sensor (FP/AgNWs@ZIF-8) consisting of silver nanowires and zeolite imidazole frameworks combined with filter paper was prepared for the sensitive and rapid detection of thiram on fruit peel surfaces. The effect that different coating cycles of ZIF-8 films exert on the Raman signal enhancement of the sensor was investigated. The results show that optimal Raman response to 4-Aminothiophenol (4-ATP) was demonstrated in the FP/AgNWs@ZIF-8(5) sensor, with a low LOD of 1.6 × 10−15M due to a coating period of 5. Furthermore, a novel SERS FP/AgNWs@ZIF-8 sensor with a porous and flexible structure on low-cost and eco-friendly paper was obtained, as to be immersed in a solution of thiram or wiped on a nectarine skin surface, and the highly sensitive LODs of 1.4 × 10−12M and 7.4 fg/cm2were achieved, respectively. Therefore, this facile, rapid, and sensitive flexible sensor at low-cost has excellent potential for pesticide residue detection and environmental toxicity analysis.

(1−x)PbZrO3–xSrTiO3(x: 10, 20, and 30 mol %) ceramics were prepared by a conventional mixed‐oxide solid‐state reaction method. The relaxer behaviors of the PbZrO3–SrTiO3ceramics were examined in the temperature range of 120–523 K. A broad dielectric maximum that shifted to higher temperature with increasing frequency signified the relaxer‐type behaviors of these ceramics. The value of the relaxation parameter of γ=1.73, estimated from the linear fit of the modified Curie–Weiss law, indicated the relaxer nature. High‐temperature dielectric relaxation phenomena were found in the temperature region of 600‐850 K. The activation energy, calculated from impedance measurements of samples, suggested that the dielectric relaxation was a result of oxygen vacancies generated during the sintering process. The energy‐storage density calculated from hysteresis loops reached about 0.46 J cm−3for the PSZT30 ceramic at room temperature. Solid‐solution storage: In the polarization/electric field plot for the PSZT30 ceramic, typical double hysteresis loops manifest the antiferroelectric phase at room temperature. For evaluation, the blue and gray areas represent the energy‐storage and energy‐loss densities (Jrecoand Jloss), respectively. The electric‐field‐related energy‐storage properties of the PSZT30 ceramic (inset) show that the Jrecoand Jlossvalues increase as the electric field increases.

Antibiotics play an essential role in the treatment of various diseases. However, the overuse of antibiotics has led to the pollution of water bodies and food safety, affecting human health. Herein, we report a dual-emission MOF-based flexible sensor for the detection of antibiotics in water, which was prepared by first encapsulating rhodamine B (RhB) by a zeolite imidazolium ester skeleton (ZIF-8) and then blending it with polyvinylidene difluoride (PVDF). The luminescent properties, structural tunability, and flexible porosity of the MOF-based composites were combined with the processability and flexibility of polymers to prepare luminescent membranes. The sensor is capable of dual-emission ratiometric fluorescence sensing of nitrofurantoin (NFT) and oxytetracycline (OTC), exhibiting sensitive detection of fluorescence burst and fluorescence enhancement, respectively, with detection limits of 0.012 μM and 8.9 nM. With the advantages of visual detection, high sensitivity, short detection time, and simplicity, the highly sensitive ratiometric fluorescent flexible sensor has great potential for detecting antibiotics in an aqueous environment. It will further stimulate interest in luminescent MOF-based mixed matrix membranes and their sensing applications.

Flexible tactile sensors with high sensitivity, a broad pressure detection range, and high resolution are highly desired for the applications of health monitoring, robots, and the human–machine interface. However, it is still challenging to realize a tactile sensor with high sensitivity and resolution over a wide detection range. Herein, to solve the abovementioned problem, we demonstrate a universal route to develop a highly sensitive tactile sensor with high resolution and a wide pressure range. The tactile sensor is composed of two layers of microstructured flexible electrodes with high modulus and conductive cotton fabric with low modulus. By optimizing the sensing films, the fabricated tactile sensor shows a high sensitivity of 8.9 × 104kPa–1from 2 Pa to 250 kPa because of the high structural compressibility and stress adaptation of the multilayered composite films. Meanwhile, a fast response speed of 18 ms, an ultrahigh resolution of 100 Pa over 100 kPa, and excellent durability over 20 000 loading/unloading cycles are demonstrated. Moreover, a 6 × 6 tactile sensor array is fabricated and shows promising potential application in electronic skin (e-skin). Therefore, employing multilayered composite films for tactile sensors is a novel strategy to achieve high-performance tactile perception in real-time health monitoring and artificial intelligence.

The Al2O3 ceramics with high thermal conductivity prepared the spark plasma sintering (SPS) technology. The structure, image and magnetic properties of the SPS Al2O3 ceramics was characterized by X-ray, field emission scanning electron microscope (FE-SEM) and the vibrating sample magnetometer (VSM) at room temperature. The results shown that the average grain size of the Al2O3 ceramics is about 5~15μm, the thermal conductivity of Al2O3 ceramics up to 24.928 W/(m·K), and the remanent magnetization as higher as 0.00546emu/g and the saturation magnetization as higher as 0.0321 emu/g, respectively. The room-temperature ferromagnetism, which is different from the traditional, possibly originates from the oxygen vacancies.

Bi0.9Nd0.1FeO3 (BNFO) films were deposited on Si (100) and (La,Sr)(Al,Ta)O3 (100) (LAST) substrate by radio frequency (RF) magnetron sputtering method respectively. The structure，morphology and magnetic properties were studied. X-ray diffraction (XRD) result indicates that the BNFO films on different substrate adopted different orientation. Cross-section scanning electron microscopy shows that the film thickness is 145 nm．Magnetic properties measurement shows that the film on Si(100) substrate has the larger saturation magnetization (Ms) of 3 686 emu/cm3, while the Ms value of the BNFO films on LSAT(100) substrate is only 1 213 emu/cm3.

In this work, (Ba0.65Sr0.35)TiO3 (BST) and Ba(Zr0.20Ti0.80)O3 (BZT) ceramic targets were prepared using the traditional solid-state reaction technique, which were sintered at 1200 C for 2 h. The thin films of BST, BZT and sandwich structure BST/BZT/BST were grown on Pt/Ti/SiO2/Si(100) and Si(100) substrates by rf-sputtering at 500 C, respectively. And all samples crystallied at temperatures 650 C for 30 min in oxygen atmosphere. The cross-sectional images of the thin films were characterized by scanning electron microscope (SEM). The dielectric constant and dissipation factor tan of the BZT, BST and BST/BZT/BST thin films are 680 and 0.030, 240 and 0.021, 85 and 0.018, respectively at 100 kHz. Compared with BST and BZT films, the BST/BZT/BST film has lower dielectric constant and lower dissipation. The remanent polarization (Pr) of the sandwich structure BST/BZT/BST thin film is up to 9.57 μC/cm2, the Pr value is larger than that BST (0.25μC/cm2) film and BZT (8.45μC/cm2) film. The optical properties (refractive index n and extinction coefficient k) of the BST/BZT/BST film on Si(100) substrate were measured by n & k analyzer 2000.

Bi3.4Nd0.6Ti3O12 (BNT) thin films have been prepared on Si (100) substrate by RF magnetron sputtering method. The crystalline structures were studied by X-ray diffraction. The surface of the films have been observed by SEM. The reflectivity was measured by n & k Analyzer 2000 with the wavelength from 190 to 900 nm. The optical constant, thickness and the forbidden band gap were fitted. The results showed that with the annealing temperatures raised from 600 to 750 C, the reflectivity index decreased from 2.224 to 2.039, and the forbidden band gap decreased from 3.19 to 2.99 eV. The possible mechanism of the effect of annealing temperature on the optical properties was discussed.

The 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (abbreviated to BNT-BT) powder and ceramic was synthesized by sol-gel process. The phase structure and dielectric properties of the ceramics were investigated. The ceramic was sintering at 1000-1100 degree C for 2-4 h in air atmosphere, and the X-ray diffraction (XRD) results revealed that the samples was pure perovskite-type phase. The Curite temperature of BNT-BT ceramics was high up to 348 degree C. The temperature dependence of dielectric permittivity and loss revealed there were two phase transitions, which were from ferroelectric (tetragonal) to anti-ferroelectric (rhombohedral) and anti-ferroelectric to paraelectric (cubic) in BNT-BT ceramics. Diffuse phase transitions were observed in BNT and BNT-BT ceramics and the Curie-Weiss Exponent (CWE) were nearly 2.

Lead strontium zirconate titanate (Pb0.92Sr0.08)(Zr0.65Ti0.35)O3 (PSZT) thin films were grown on Pt (111)/Ti/SiO2/Si(100) substrates using a simple sol-gel method. X-ray diffraction studies confirmed that all the PSZT films undergone various thermal process show highly preferred (001)-orientation. On the surface image of the thin film, many clusters are found, which are composed by grains in size of 0.5-0.8 mm. Between the clusters, the nano-size grain is about 50-80 nm. The root mean square (RMS) roughness of the film surfaces is 5.1 nm. PSZT thin film exhibit excellent ferroelectric behavior, demonstrated by reproducible hystersis loops with high remnant polarization (Pr =49 μC cm-2) and relative low coercive field (Ec=53.5 kV cm-1). The pyroelectric coefficients (p) were measured, at 26 oC, the p=215 mC m-2 K-1 for PSZT films. The dielectric properties as well as phase transition behavior were characterized and a ferroelectric to paraelectric transition were found in the vicinity of 196 °C.

In this work, effect of low sintering temperature and time on the new lead-free perovskite (Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3 (BCZT) solid solution ceramics have been investigated. X-ray diffraction (XRD) was used to understand the phase transition of the BCZT during heating. The Curie temperature decreased nonlinearly 43 K in BCZT ceramics. Diffuse phase transitions were observed in BCZT ceramics and the Curie-Weiss exponent (CWE) was nearly 2. The dielectric permittivity versus temperature characteristics and the γ in the modified Curie-Weiss law, as a function of the dc bias field was obtained for BCZT ceramics. The fitting of parameters (Tm vs. f ) have close agreement with the data of Vogel-Fulcher’s relationship.

Two kinds ceramics of pure CaCu3Ti4O12 (CCTO) and Sr/Mg doped (Ca0.25Cu0.75)0.5Sr0.5TiO3 + xMgO (x=0.01, 0.03, 0.05, 0.1, denoted as CCST-M-1, CCST-M-3, CCST-M-5, CCST-M-10, respectively) were prepared using the traditional solid phase reaction method. The dielectric properties were measured by HP 4194A Impedance/Gain-Phase Analyzer with the frequency range from 100 Hz to 1MHz. The temperature dependence of dielectric constant and loss tangent were measured for different frequencies. The variation relation of the critical temperature with the frequency was fitted theoretically which is in agreement with the Arrhenius law for pure CCTO. According to a variable power law to describe the paraelectric dielectric constant of ferroelectrics with diffuse phase transitions, the theoretical fitting was carried out for doped samples, and it was suggested that all doped samples exhibited the Debye-like relaxation. Among the doped and pure CCTO samples, CCST-M-1 was of the lowest dielectric loss at the whole measurement frequency, and whose I–V response curve was nonlinear suggesting a non-ohmic contact. The complex-impedance analysis results showed that the reduction in dielectric loss of CCST-M-1 sample can be attributed to the increase of grain boundary resistance. It is expect that these results are helpful to promote the CCTO-related materials to practical applications.

Bismuth neodymium ferrite (Bi1-xNdxFeO3: BNFO; x=0, 0.025, 0.075, 0.125, 0.175) ceramics were prepared by a co-precipitation method and sintered at 800 °C, using nitrates as precursors. The crystal structure and dielectric properties of the samples were characterized by X-ray diffraction （XRD）and dielectric permittivity measurement at different temperatures and frequencies. XRD suggests that the impurity phases are weakened by suitably doping x=0.075. Dielectric spectra indicate that relaxation peaks below the Néel temperature which may be produced by the effect of grain boundaries and dipoles with heating vanish after doping Nd at the same content. Complex impedance spectra manifest that the doped samples are closer to Debye-type, and the impedance rises which will lead to low leakage current.

Lead-free ceramics with the composition of Mn-doped Ba(Zr0.06Ti0.94)O3 – xmol%MnO2 (BZT6-xMn, x=0, 1 and 2) have been synthesized by a mixed oxide process. Structure and micrograph characterization were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM), which revealed that all samples have the orthorhombic phase with dense and the uniform microstructure. The grain size of Mn-doped BZT6 ceramics decreased with increasing MnO2 doping. The effect of MnO2 doping on the dielectric and ferroelectric properties was also investigated. The maximum dielectric permittivity decreased dramatically with increasing MnO2 doping in the BZT6 ceramics. A peculiar double-hysteresis-like loop was observed. Mn ions as acceptor doping occupy the B site of ABO3 in the form of Mn2+ and Mn3+, which brought an increase in the oxygen vacancies concentration. The defect dipole model was explained the pinning mechanism.

(Pb1-xBax)ZrO3 (PBZ) ceramics for x = 0.10 were synthesized by the mixed oxide solid state reaction method. Phase transition was investigated by dielectric measurements in the temperature range from 27 to 350 °C at various frequencies. The permittivity of the solids corresponding to (Pb1-xBax) ZrO3 showed the maximum value of 10220 at x = 0.10 at the phase transition temperature. The maximum permittivity gradually increasing concentration up to x = 0.10. The ferroelectric hysteresis loop of the PBZ ceramics for x = 0.10 is displayed at room temperature and 0.2 Hz.

Pb(ZrxTi1-x)O3 (PZT, x=0, 0.8, 1) thin films on fused quartz and Pt-coated Si substrates were prepared by a modified sol-gel process. Without using reflux and distillation to remove water. Phase structure, refractive indices n of amorphous and polycrystalline PZT thin films were obtained by X-ray diffraction, spectroscopic ellipsometry, and UV-VIS spectroscopy. PbZrO3 thin films on fused quartz substrates annealed at various temperatures, the absorption edges shifted is mainly due to phase structure changed from amorphous to polycrystalline. The refractive indices n of crystalline PbZrO3 thin film on Pt-coated Si substrates, compared with that of crystalline thin films of PbTiO3 and PZT80/20 were discussed.

More and more researchers start to pay attention to the electrocaloric temperature change (ΔT) in polar materials, which is caused by an applied electric field. In this paper, Ba-doped PbHfO3(PBH) films were prepared by sol-gel method. Their components, microstructures, dielectric polarization and electrocaloric effects (ECEs) were investigated. With the addition of Ba2+, PBH films went from antiferroelectric (AFE) to ferroelectric (FE). At the same time, their dielectric peaks shifted toward lower temperature. The maximum ΔTobtained in Pb0.8Ba0.2HfO3FE film is 41.1 K, which is an order of magnitude larger than PbHfO3film (ΔT ∼ −4 K at 50 °C) and Pb0.9Ba0.1HfO3film (ΔT < 4 K at 120 °C). In order to explain this phenomenon, the Landau-Devonshire theory was adopted. Our analysis shows that the rapid variation of energy barrier height near the phase transition temperature is beneficial to obtain large polarization change and high △T, which is needed in solid-state cooling devices.

Calcium modified lead titanate (PCT) thin films have been prepared by spin-coating of solutions on Si(100) and LaAlO3(100) substrates. The thin films were characterized by x-ray diffraction, scanning electron microscope and Raman scattering. The PCT thin films were oriental grown on LaAlO3 substrate. Raman scattering from the PCT thin films was clearly observed. We suggest that strain exists in the films, which changes the crystal symmetry. The mechanism of orientation of the PCT films is discussed.

Resistive switching of amorphous Bismuth ferrite thin film device annealed at 500 °C.