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Dense and homogeneous BaTi1-xSnxO3 (BTS, x = 0.1, 0.15, 0.2, 0.25, and 0.3) thin films are prepared by sol-gel and spin-coating soft chemistry, which is a simple, repeatable and quality-controlled method. The effects of Sn content on the structure and dielectric properties are systemically studied. The BTS thin film with 0.25 mol% Sn is found to exhibit a moderate dielectric constant of 225–398, a high tunability of 43.3% under a low bias electric field of 8 kV/mm, and a corresponding leakage current density of 6.2×10−8 A/cm2. These improvements are a result of the enhancement in relaxor characteristics, the good crystallization conditions leading to a denser and more uniform structure, as well as the inhibition of oxygen vacancies resulting from the suppression of electronic transition from Ti4+ to Ti3+. The findings reported in this work provide a simple and effective way to prepare excellent tunable thin films that show great potential for the development of electrically tunable components and devices.

In the present work, we used a hybrid ceramic fabrication technology to synthesize lead zirconate titanate (PZT) piezoelectric ceramics coated with yttrium oxide–stabilized zirconia (YSZ) powders (PZT@YSZ). The tailoring effects of the YSZ grain coating layer were investigated systematically. The results demonstrate that the mechanical properties of the modified PZT ceramics were successfully improved, which is mainly attributed to the synergistic effect of reinforced martensitic transformation toughening, micro-crack toughening, and second-phase dispersion toughening of the YSZ grain coating layer. More importantly, the piezoelectric properties of the PZT@YSZ ceramics, such as d33, kp, strain (S), strain hysteresis Hs, and d33*, have no declined, instead, have improved significantly. This is due to the coexistence of the rhombohedral-tetragonal phase of PZT in the PZT@YSZ ceramics, which is confirmed by Rietveld refinements in X-ray diffraction. Furthermore, the breakdown strength of the PZT@YSZ ceramics increased by 28%, a result of the reduction in grain size. This work describes an effective approach to simultaneously toughening PZT-based piezoelectric ceramics and enhancing their piezoelectric properties.

In this work, a new core-shell structure of antiferroelectric ceramic powder (Pb0.97La0.02Zr0.85Sn0.12Ti0.03O3-PLZST) coated with linear dielectric (Al2O3) has been successfully prepared to realize high energy density through tape-casting process. According to the experimental results of electron microscope, the sol-gel derived Al2O3 layer was uniformly coated on the PLZST particles and the Al2O3 layer can be taken as the buffer layer to effectively refine the grain growth as well. Therefore, the modified PLZST particles were fine and uniform compared with the pure PLZST. It was found that the buffer layer could undertake higher electric field and the electric field applied to PLZST particles was weakened based on finite element analysis, which can avoid the premature breakdown of PLZST. And the actual measured breakdown strength was significantly enhanced from 22.2 kV/mm to 35.5 kV/mm. Correspondingly, an extremely high recoverable energy storage density of 5.3 J/cm3 was obtained for PLZST with 0.5%wt Al2O3, an 204% enhancement over the pure PLZST ceramics (2.6 J/cm3), and the corresponding efficiency was up to 88.3%. In addition, impedance spectroscopy measurement was carried out to further confirm the better insulation of the ceramic with Al2O3 buffer.

A novel piezoluminescent (PZL) phosphor was prepared by doping Pr3+ ions into ferroelectric LiTaO3 matrices, and their crystal structure and multi-luminescent performance were investigated. A slightly Li-rich nonstoichiometric design gave the phosphors optimized PZL behavior with favorable recoverability. Excited by 240 nm radiation, two strong photoluminescent (PL) emission bands lay around 511 and 615 nm, which corresponded to Pr3+ transitions of 3P0 to 3H4 and 1D2 to 3H4, respectively. Nevertheless, the 3P0 to 3H4 transition was detectably suppressed in AG/PZL spectra with 1D2 to 3H4 becoming dominant, which was possibly owing to the effect of trap level distribution on direct tunneling possibilities. In this context, a probable mechanism was proposed to explain the multi-luminescent process in LiTaO3:Pr3+. This study was aimed at exploring novel PZL materials for fundamental research and applications in multifunctional devices.

Taking Al as top electrode, a repairing layer with ultrahigh dielectric strength and resistivity was generated at the interface between sol-gel Al2O3 films and electrodes under the applied electric field. This repairing layer effectively restored the defects on the film surface and improved the dielectric strength. More importantly, it was found that adding ZrO2 nanoparticle into the matrix film could further enhance the dielectric strength, since the ZrO2 nanoparticle is conductive to forming the interfacial repairing layer. The analysis of ac conduction properties showed that the introduction of nano-ZrO2 resulted in a lower potential barrier and a longer hopping distance for ionic migration. In addition, the simulation result indicated that nano-ZrO2 addition induced a local region of high electric field that accelerated ionic migration. As a result of the two factors, the nanocomposite structure of Al2O3/nano-ZrO2 is capable to provide more ions for the formation of interfacial repairing layer. With the stronger repairing behavior, Al2O3/nano-ZrO2 composite films exhibited significantly enhanced breakdown strength of ~ 576 MV/m and energy density of 14.7 J/cm3, in contrast with 385 MV/m and 5.9 J/cm3 for pure Al2O3 films with Al electrodes.

Process of self-growth nanocrystalline structure was explored to improve the dielectric properties of amorphous Sr0.925Bi0.05TiO3 (SBT) thin films through controlling the annealing temperature. The crystallinity of the material was 15% when annealed at 550 °C, and the resulting nanocrystalline particles were 14 nm in size as determined by XRD analysis. Therefore, the proposed process could produce a novel film of an amorphous matrix coating nanocrystalline particles. Finite element analysis results showed that the applied electric field was focused primarily in the amorphous matrix, which could effectively decrease the probability of low voltage breakdown of the nanocrystalline particles. Simultaneously, the nanocrystalline particles supplied more polarization charges, which helped to improve the dielectric constant of the inorganic composite. Combining the merits of amorphous and crystalline phases, the ultimate energy storage density of the modified sample was as high as 21.2 J/cm3, which represents an improvement of 5.1 J/cm3 compared with that of pure amorphous SBT thin film.

The different Si-Mg co-doping content was explored to improve the dielectric properties of amorphous Al2O3 thin film. According to the analysis of DSC, FT-IR, and XPS spectra, it can be confirmed that a novel structure of glass network is formed in the co-doped Al2O3 thin film. More importantly, compared to Al2O3 thin film, the leakage current of (Al.97Si.02Mg.01)2Oy thin film is reduced by 2 orders of magnitude and the breakdown strength is improved from 276 MV/m to 544 MV/m. The corresponding energy density of the modified sample is up to 9.2 J/cm3, which is an enhancement of 6.2 J/cm3 over that of the undoped Al2O3 thin film. Based on finite element analysis, the simulation results show that the applied electric field is mainly focused on the glass network, which could strengthen the stability of Al2O3 structure and decrease the breakdown probability of the films. From the viewpoint of defect chemistry, another reason for the enhancement of the dielectric properties is that Si-Mg co-doping results in the generation of cation vacancies and thus the formation of oxygen vacancies could be effectively prevented. This work could provide a new design strategy for high-performance dielectric capacitor devices.

SrTiO3-based films doped with different Al-precursors were prepared by sol-gel methods and the dielectric strengths and leakage currents of the materials were investigated. The best performance was found in SrTiO3 films doped with Al2O3 nanoparticles (nano-Al2O3). When 5 mol% of nano-Al2O3 was added to SrTiO3 films with Al electrodes, the dielectric strength was enhanced to 506.9 MV/m compared with a value of 233.5 MV/m for SrTiO3 films. The energy density of the 5 mol% nano-Al2O3 doped SrTiO3 films was 19.3 J/cm3, which was also far higher than that of the SrTiO3 films (3.2 J/cm3). These results were attributed to interfacial anodic oxidation reactions, which were experimentally confirmed by cross-sectional transmission electron microscope studies and theoretically modelled based on Faraday's laws. The films with added nano-Al2O3 featured many conducting paths at the interfaces between the host phase and the guest nano-Al2O3, which promoted ion transport and contributed to the strong anodic oxidation reaction capability of the 5 mol% nano-Al2O3 doped SrTiO3 films.

Self-repairing behavior of SrTiO 3 film capacitor was explored to improve the energy density. With Au and Al being deposited on SrTiO 3 thin films as top electrode, the breakdown processes were investigated by a real-time optical microscope system. A high electric field of the electrode edge attributed to edge effect provided the “trigger factor” for the self-repairing behavior. Absorbed water not only provided “mobile phase” for self-repairing process which significantly enhanced breakdown strength but also, and equally important, it supplied additional polarization charges to raise dielectric constant. As a result of the concurrent increase in E b and e r , a higher energy density of 15.7 J/cm 3 is achieved. A leakage current platform was observed in the self-repairing process and the thickness of a new layer Al 2 O 3 film generated from self-repairing process was estimated according to Ohm's law and breakdown strength. Using relative humidity dependence of breakdown voltage, the maximum breakdown field was explored to realize the optimum self-repairing capability.

In this work, the effects of Zr 4+ addition on the phase structure and energy storage properties of (Pb 0.97 La 0.02 )(Zr x Sn 0.945−x Ti 0.055 )O 3 (PLZST) antiferroelectric (AFE) ceramics were investigated, aiming to optimize the composition for enhanced energy storage properties. Due to the substitution of Zr 4+ with larger ion radius for Sn 4+ , the tolerance factor of PLZST AFE ceramics decreased and thus the AFE state transformed gradually from tetragonal phase to orthorhombic phase with higher ferroelectric-antiferroelectric phase switching electric field ( E A ) with increasing Zr 4+ content from x=0.65–0.85. The increase of E A led to the improvement of recoverable energy density ( U re ) from 3.18 J/cm 3 (x=0.65) to 4.38 J/cm 3 (x=0.8). However, when Zr 4+ content was more than 0.8, the U re decreased from 4.38 J/cm 3 to 4.12 J/cm 3 (x=0.85) due to the reduction of the saturation polarization. The best energy storage properties were achieved in PLZST orthorhombic AFE ceramic with Zr 4+ content of x=0.8, which exhibited a maximum U re of 4.38 J/cm 3 and very small U re variation ( 0.97 La 0.02 )(Zr 0.8 Sn 0.145 Ti 0.055 )O 3 antiferroelectric ceramic is a promising material for developing high-performance pulse power capacitors usable in wide temperature range.

(Mg 0.95 Zn 0.05 ) 2 (Ti 0.8 Sn 0.2 )O 4 powder was synthesized by a solid state reaction. Then, Ni 0.4 Zn 0.6 Fe 2 O 4 was grown on the (Mg 0.95 Zn 0.05 )(Ti 0.8 Sn 0.2 )O 4 particles in a hydrothermal environment to form a core-shell structure. (1- x )(Mg 0.95 Zn 0.05 ) 2 (Ti 0.8 Sn 0.2 )O 4 @ x Ni 0.4 Zn 0.6 Fe 2 O 4 composite ceramics were sintered at 1200 °C with these powders. XRD, SEM, TEM analyses indicated that high dense core-shell ceramics without any foreign phase were obtained. Different types of sharp interfaces were self-assembled owing to the minimization of direct elastic energy in the hydrothermal environment. The composites enjoy good magnetic and dielectric properties, especially, good microwave dielectric properties with high saturation magnetization when the ferrite content is 0.3–0.5. The results provided a powerful experimental basis for the sensor and transducer.

Dielectric (1-x)SrTiO 3 /xSiO 2 (x=0, 0.01, 0.05 and 0.1) composite thin films were deposited onto Pt (100)/Ti/SiO 2 /Si substrates via sol-gel and spin coating technology and their surface morphology was examined by field emission scanning electron microscopy, indicating that surface morphology was apparently influenced by the nano-SiO 2 addition. A broad adsorption band at 3200–3500 cm −1 attributed to stretching vibrations of O-H bonds in the absorbed water was observed in fourier transform infrared spectroscopy (FTIR). The X-ray photoelectron spectroscopy (XPS) results show that nano-SiO 2 particles facilitate water absorption of STO thin films. The breakdown strength of SrTiO 3 /nano-SiO 2 composite films is increased to about 332 MV/m. At the same time, the leakage current of 0.9SrTiO 3 /0.1SiO 2 composite thin films decreases by two orders of magnitude under high electric field. Above results show that nano-SiO 2 particles facilitate water absorption of the thin films, making SrTiO 3 act as an effective solid state electrolyte for the anodic oxidation to achieve higher breakdown strength.

Dielectric Al 2−2 x La 2 x O 3 ( x =0.00, 0.005, 0.02, 0.05, and 0.10) thin films were fabricated on Pt/Ti/SiO 2 /Si substrates by sol–gel spin coating. The surface morphology of Al 2−2 x La 2 x O 3 thin film was observed by field emission scanning electron microscopy. The chemical state of the lanthanum in aluminum oxide films was analyzed using X-ray photoelectron spectroscopy (XPS), indicating that lanthanum reacts with absorbed water to form lanthanum hydroxide. J–E measurements were used to investigate the current conduction mechanism and breakdown behavior. The results show that La doping changes the conduction mechanism and makes influences on leakage current. The dominating conduction process of 10% La doped Al 2 O 3 films turns into the space charge limited current (SCLC) mechanism in the field region ranging from 25 to 150 MV/m. The leakage current of the films with 10% La doping decreases by three orders of magnitude from 10 −6 to 10 −9 at the electric field of 25 MV/m. The breakdown strength increases with the increasing content of lanthanum.

Using Al(NO 3 ) 3 ·9H 2 O as a precursor, optically transparent Al 2 O 3 thin films have been successfully synthesized by combining a sol–gel spin-coating process with one of two different annealing methods. One set of samples was subjected to a conventional annealing process (C.A) at 700 °C for 2 h in a muffle furnace, while the other set was exposed to a microwave annealing process (M.A) at 700 °C for 30 min in a microwave oven at 2.45 GHz. The structure, morphology, composition, stoichiometry, chemical bonding and optical properties of the films were investigated by X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and UV–vis–NIR spectrophotometry. XRD, FTIR and XPS investigations confirm that both the C.A and M.A films consist of amorphous Al 2 O 3 with a certain amount of chemisorbed oxygen, and both Al 2 O 3 films have a transmittance of at least 92% in the wavelength range of 400–1200 nm. However, compared to the C.A film, the M.A films have an even higher transmittance, a wider optical band gap and a lower refractive index.

A new Aurivillius oxide Na0.5Er0.5Bi4Ti4O15 (NEBT) was synthesized by conventional solid-state reaction and characterized by X-ray diffraction, scanning electron microscope, luminescent, dielectric, and piezoelectric measurements. The as-prepared NEBT ceramics showed a bright upconversion photoluminescence (UC) while simultaneously exhibited a piezoelectric characteristic. Under 980 nm radiation excitation, three emission bands located at green (532 nm, 556 nm) and red (671 nm) wavelength regions were obtained at room temperature. The fluorescence intensity ratio of two green emission bands (centered at 532,556 nm) was studied as a function of temperature in a range of 173–503 K. The maximum sensor sensitivity was found to be about 0.0017 K−1 (380 K). Dielectric property studies showed that NEBT had a phase transition from ferroelectric to paraelectric at around 665 °C. The annealing temperature dependence of piezoelectric d33 showed stably thermal piezoelectric properties of NEBT. As a multifunctional material, NEBT would be useful in sensor, future optical-electro integration devices.

Dense and crack-free aluminum oxide films were fabricated by sol–gel spin-coating technology. Aluminum nitrate (Al(NO 3 ) 3 .9H 2 O) was used as the precursor material. X-ray diffraction shows that the fabricated films are amorphous. X-ray photoelectron spectroscopy confirms that the thin films are alumina (Al 2 O 3 ). Field-emission scanning electron microscopy images of the films reveal that the films are compact with a dense cross section. Dielectric measurements were carried out on samples with a metal–insulator–metal structure. The electrical characteristics of the films were affected by the thermal sintering temperature of the films. The leakage current density of the films decreases with the increase in the sintering temperature and increases with the increase in the measuring temperature. The leakage current shows a linear dependence on the voltage in the low-electric field-regime. The current density ascends to higher values due to the effect of space charges in the high-electric-field regime. The ionization energy of the top-electrode metals (Au, Pt or Ti–Au) has a strong effect on the leakage current.

(1− x )Ba 0.5 Sr 0.5 TiO 3 – x Mg 2 TiO 4 composite ceramics were synthesized in situ by the hydrothermal method and their structure and dielectric properties were investigated systematically. Results showed that a ferroelectric–dielectric composite containing Ba 0.5 Sr 0.5 TiO 3 and Mg 2 TiO 4 phases could be successfully synthesized at sintering temperatures below 1300 °C. As the sintering temperature increased, the dielectric peaks of the cubic-tetragonal phase transition were markedly enhanced and sharpened and shifted toward high temperature. As the concentration of Mg 2 TiO 4 increased, both permittivity ( e ) and tunability ( T ) decreased, whereas Q value firstly increased and then decreased. The sample with x =0.6 exhibited good microwave dielectric properties, with e of 136, Q of 342 (at 3.804 GHz) and T of 16.2%, which make it a potential candidate for the fabrication of tunable microwave devices.

(Pb0.97Ba0.02)Nb0.02(Zr0.55Sn0.45−xTix)0.98O3 (PBNZST, 0.03≤x≤0.06) ceramics were prepared by conventional solid state synthesis and their crystal structure, ferroelectric, dielectric, and electric field-induced strain properties were systemically investigated. A transformation from antiferroelectric (AFE) phase to ferroelectric (FE) phase was observed at 0.05

An improved coprecipitation method using buffer solution was developed for synthesizing Pb 0.97 La 0.02 (Zr 0.75 Ti 0.08 Sn 0.17 )O 3 antiferroelectric ceramics. It was found that the perovskite phase was formed when the precursor powders were calcined at 550 °C for 2 h and the average diameter of these particles was less than 100 nm. Moreover, the results showed that when the pH value of the precipitating solution was in the range of 8.9–9.0, in comparison with the ceramics prepared by conventional solid state reaction, the samples synthesized by coprecipitation method had a larger electric field-induced phase transition and higher breakdown strength, which lay a basis for preparing high power energy storage capacitors and pulsed power applications.

A comparative study on the dielectric properties of Ba 1− x Sr x TiO 3 ( x =0.1–0.6) ceramics prepared by microwave sintering (MS) and conventional sintering (CS) has been done. It was found that MS samples need lower temperature and much shorter time than CS samples to obtain the same degree of densification. Compared with CS samples, MS samples possessed smaller grain size, better densification and more uniform grain growth. The dielectric properties of the samples were measured as a function of temperature. It was observed that the dielectric constant was higher for MS samples compared with that of CS samples especially in the ferroelectric phase.

(1 − x )Ba 0.4 Sr 0.6 TiO 3 – x BaMoO 4 ceramics with x = 5, 10, 20, 30, 40 and 60 wt% were prepared by traditional solid-state reaction method. Two crystalline phases, a cubic perovskite structure Ba 0.4 Sr 0.6 TiO 3 (BST) and a tetragonal scheelite structure BaMoO 4 (BM) were obtained by XRD analysis. The microwave dielectric properties of Ba 0.4 Sr 0.6 TiO 3 –BaMoO 4 composite ceramics were investigated systematically. The results show that the composite ceramics exhibited promising microwave properties. The dielectric constant can be adjusted in the range from 900 to 78, while maintaining relatively high tunability from 27.3% to 12.8% under a direct current electric field of 60 kV/cm and Q values from 619 to 67 in the gigahertz frequency region.

This paper investigated dielectric properties of rare earth (Dy, Tb, Eu)-doped barium titanate sintered in pure nitrogen. The substituting concentration of rare earth (Dy, Tb, Eu) was 2.0 mol%. The doping behaviors of intermediate rare-earth ions (Dy, Tb, Eu) and their effects on the dielectric property of barium titanate were investigated. Eu 3+ ion was substituted in the A-site of the perovskite lattice. Dy 3+ and Tb 3+ ions substituted partially for Ti 4+ site and partially for Ba 2+ site. The different rare earth element had a crucial effect on dielectric properties of rare-earth-doped BaTiO 3 . Among these doped samples, Tb-doped BaTiO 3 had the largest dielectric constant (70,000–80,000); the smallest dielectric loss (less than 4%), and good capacitance-temperature coefficient, which satisfies the X7R specification of the Electronic Industries Association Standards (TCC within ±15% from −55 °C to 125 °C).

This paper investigated the low-frequency mechanical properties of ferroelectric ceramics (PZT-5H and PZT-8) and anti-ferroelectric ceramics ((Pb 0.97− x Ba x La 0.02 )(Zr 0.50 Ti 0.10 Sn 0.40 )O 3 , x = 0.08, 0.09, 0.10, 0.11) by a dynamic mechanical analyzer (DMA). The dynamic mechanical analysis was performed from −100 to 400 °C in temperature and 0.1–4 Hz in frequency. The dielectric properties were also measured as a comparison. The results showed an obvious turning point ( T m ) where tan δ reached its maximum and the modulus began to increase for all the samples. tan δ revealed an relaxation region in the ferroelectric ceramics and no corresponding region in the anti-ferroelectric ceramics, which may be originated from the domain walls’ motion in the ceramic. The tan δ started to decrease to nearly zero around the tetragonal to cubic phase transition temperature ( T c ) for all of the tested samples.

In this paper, we reported on a novel, simple, and cost-effective chemical route to fabrication of thermoelectric films, such as Bi, PbTe, and Bi 2 Te 3 . The films were prepared by spinning coating corresponding metastable precursor solutions, using TeO 2 and/or metallic salt as the starting materials, and KBH 4 as reductant. The phase structure and morphology of the films were characterized by X-ray diffraction and field-emission scanning electron microscopy, respectively. The formation mechanisms of the films were proposed. The electrical conductivity of the films was measured at room temperature.

Textured K 0.5 Na 0.5 NbO 3 thick film was prepared by the reactive templated grain growth method. The effects of Mn 2+ doping on the phase structure, microstructure and electrical properties of the K 0.5 Na 0.5 NbO 3 textured thick film were investigated. The grain orientation degree decreased with increasing Mn 2+ and reduced to 50% for the thick film with 5 mol% Mn 2+ . The addition of Mn 2+ improved the microstructure of the thick film. The electric properties of the thick film were also enhanced because of the high densification, the vacancy compensation effect and the acceptor doping effects of Mn 2+ . The K 0.5 Na 0.5 NbO 3 thick film with 2 mol% Mn 2+ doping possessed the optimum properties: P r = 3.05 μC/cm 2 , E c = 4.79 kV/cm, J = 4.6 × 10 −6 A/cm 2 (at 25 kV/cm) and d 33 * = 124 pm/V .

The mechanoluminescence (ML) properties of Pr 3+ -doped BaTiO 3 –CaTiO 3 diphase ceramics in different stressed conditions have been investigated. The results indicate that this ML belongs to elastico-ML (EML) and possesses the advantages of intense emission, non-destruction, repeatability of luminescence, and linear relation between the luminescence intensity and the stress. This EML is considered to have a piezoelectric origin. Furthermore, this material shows superior water resistance property.

With the rapid development of low power devices, the technology of energy harvesting has improved greatly. The performance of a PZT diaphragm energy harvester is demonstrated in this paper. Under an acceleration of 9.8 m/s 2 , a pre-stress of 1.2 N applied on the harvester, a power of 12 mW was generated at the resonance frequency of the harvester (113 Hz) across a 33 k ohm resistor. It was found that the energy from the harvester increases while its resonance frequency decreases when the pre-stress increasing. The contacting part between the proof mass and the piezoelectric disc was found another key element, which would influence the performance of the harvester. With its simple structure, the diaphragm harvester may push energy harvesting devices towards practical applications.

Ba 0.5 Sr 0.5 TiO 3 –Mg 2 (Ti 0.95 Sn 0.05 )O 4 composite ceramics have been synthesized by the solid-state reaction. Phase structure, microstructure and microwave dielectric properties have been systematically characterized. The permittivity is tailored to a certain extent with the addition of Mg 2 (Ti 0.95 Sn 0.05 )O 4 . Both X-ray diffraction (XRD) and back electric image (BEI) analysis show the co-existence of two-phase structures of ABO 3 perovskite and A 2 BO 4 spinel structure. A high dielectric tunablity can be obtained and a high Q value can be achieved at microwave frequency. The composition 30 wt.%Ba 0.5 Sr 0.5 TiO 3 –70 wt.%Mg 2 (Ti 0.95 Sn 0.05 )O 4 exhibits good dielectric properties with ɛ of 79, Q of 152 (at 2.997 GHz) and T of 15.8% (30 kV/cm & 10 kHz) at room temperature, which make it a promising candidate for tunable microwave device applications in the wireless communication system.

Ba 0.6 Sr 0.4 TiO 3− x MgCo 2 (VO 4 ) 2 ceramics with x = 0, 0.5, 1.0, 2.0, and 5.0 wt% was fabricated via conventional solid-state reaction process. The effects of such additives on the structure, dielectric and tunability properties were systemically investigated. A small number of secondary phase identified as Ba 3 (VO 4 ) 2 appeared in Ba 0.6 Sr 0.4 TiO 3− x MgCo 2 (VO 4 ) 2 ceramics when x is more than 5.0 wt%. With increasing of MgCo 2 (VO 4 ) 2 content, the peak values of permittivity gradually decreased and shifted to low temperature. The Ba 0.60 Sr 0.40 TiO 3 added with 0.5 wt% MgCo 2 (VO 4 ) 2 possesses a dielectric constant of 2763, Q value of 267 at ∼1 GHz and tunability of 35.9% under dc electric field of 30 kV/cm at 10 kHz.

Bi 2 Zn 2/3 Nb 4/3 O 7 thin films were deposited at room temperature on Pt/Ti/SiO 2 /Si(1 0 0) and polymer-based copper clad laminate (CCL) substrates by pulsed laser deposition. Bi 2 Zn 2/3 Nb 4/3 O 7 thin films were deposited in situ with no intentional heating under an oxygen pressure of 4 Pa and then post-annealed at 150 °C for 20 min. It was found that the films are still amorphous in nature, which was confirmed by the XRD analysis. It has been shown that the surface roughness of the substrates has a significant influence on the electrical properties of the dielectric films, especially on the leakage current. Bi 2 Zn 2/3 Nb 4/3 O 7 thin films deposited on Pt/Ti/SiO 2 /Si(1 0 0) substrates exhibit superior dielectric characteristics. The dielectric constant and loss tangent are 59.8 and 0.008 at 10 kHz, respectively. Leakage current density is 2.5 × 10 −7 A/cm 2 at an applied electric field of 400 kV/cm. Bi 2 Zn 2/3 Nb 4/3 O 7 thin films deposited on CCL substrates exhibit the dielectric constant of 60 and loss tangent of 0.018, respectively. Leakage current density is less than 1 × 10 −6 A/cm 2 at 200 kV/cm.

WO 3 (0–6 mol%)-doped 0.94Bi 0.5 Na 0.5 TiO 3 –0.06BaTiO 3 lead-free ceramics were synthesized by conventional solid-state reaction. The effect of WO 3 addition on the structure and electrical properties were investigated. The result revealed that a small amount of WO 3 (≤1 mol%) can diffuse into the lattice and does not significantly affect the phase structure, however, more addition will result in distortion and enlargement of the unit cells. The maximum permittivity temperature ( T m ) is suppressed dramatically as the dopant increasing, while the depolarization temperature ( T d ) fall to the minimum with 1 mol% WO 3 additive. The remanent polarization ( P r ) was enhanced and coercive field ( E c ) was reduced by doping with WO 3 . The strain shows the largest value for 1 mol% doped sample, which is due to a field-induced antiferroelectric–ferroelectric phase transition.

(Na0.5Bi0.5)0.94Ba0.06TiO3 thin films were deposited on Pt/Ti/SiO2/Si (1 1 1) and LaNiO3/Pt/Ti/SiO2/Si (1 1 1) substrates by a sol–gel process. The phase structure and ferroelectric properties were investigated. The X-ray diffraction pattern indicated that the (Na0.5Bi0.5)0.94Ba0.06TiO3 thin film deposited on Pt/Ti/SiO2/Si (1 1 1) substrates is polycrystalline structure without any preferred orientation. But the thin film deposited on LaNiO3/Pt/Ti/SiO2/Si substrates shows highly (1 0 0) orientation (f ≥ 81%). The leakage current density for the two thin films is about 6 × 10−3 A/cm2 at 250 kV/cm, and thin film deposited on LaNiO3/Pt/Ti/SiO2/Si substrates possessed a much lower leakage current under high electric field. The hysteresis loops at an applied electric field of 300 kV/cm and 10 kHz were acquired for the thin films. The thin films deposited on LaNiO3/Pt/Ti/SiO2/Si substrates showed improved ferroelectricity.

Lead-free ferroelectric K0.5Na0.5NbO3 (KNN) films with different thicknesses were prepared by polyvinylpyrrolidone (PVP)-modified chemical solution deposition (CSD) method. The KNN films with thickness up to 4.9 μm were obtained by repeating deposition-heating process. All KNN thick films exhibit single perovskite phase and stronger (1 1 0) peak when annealed at 650 °C. The variation of dielectric constant with thickness indicates that there exists a critical thickness for the dielectric constant in the KNN films which should lie in 1.3–2.5 μm. The similar trend is observed for the ferroelectric and piezoelectric properties of KNN films. Both the remnant polarization Pr and the piezoelectric coefficient d33 of KNN thick films increase with the film thickness and become saturated after the critical thickness.

A nano-cerium dioxide hydrosol was synthesized via a sol-gel process at the range of room temperature to 65 degrees C with the nonionic surfactant PVP (polyvinylpyrrolidone). The mixture solution of cerium nitrate and urea turned out a visible chemical re

Dielectric properties of Ba0.5Sr0.5TiO3–xZn2P2O7 (x = 1, 3, 5, 10, 15 wt%) composite ceramics, which were prepared by solid-state reaction process, were intensively investigated. The results showed that the Curie temperature (Tc) of composites gradually shifted to lower temperature (−140 °C) with increasing the content of Zn2P2O7, and the dielectric constant were tuned effectively from 2020 to 107, while maintaining a relatively high tunability. Zn2P2O7 additions remarkably inhibited the grain growth of Ba0.5Sr0.5TiO3 phases, and improved the breakdown strength of samples up to 385 kV/cm. The sample with x = 10 wt% exhibited good dielectric properties (ɛr = 290, tg δ = 0.0006, T = 20.5%, BDS = 297 kV/cm). Meanwhile Zn2P2O7 addition also made the Tc far away from the room temperature, which reduced the sensitivity of the dielectric constant to temperature change and simultaneously improved the stability of materials.

The effect of Sn:Ti variations on antiferroelectric to ferroelectric phase transition of (Pb0.97La0.02)(Zr0.65Sn0.35−xTix)O3 (x = 0.08–0.11) ceramics with compositions near antiferroelectric to ferroelectric morphotropic phase boundary was studied. X-ray diffraction showed that all samples were tetragonal phase at room temperature. With the increase of x from 0.08 to 0.1, all samples showed the typical antiferroelectric double loops. The critical value EAF of the electric-field induced antiferroelectric to ferroelectric phase transition decreased from 64 kV/cm to 38 kV/cm, and the electric field EFA of induced-ferroelectric to antiferroelectric phase transition decreased from 44 kV/cm to 10 kV/cm. A high polarization of the sample with x = 0.1 can be induced with a lower electric filed. The variations of Sn:Ti ratio had no effect on hysteresis of ΔE (=EAF − EFA), but ΔE reduced with temperature increasing. The virgin sample of which x = 0.11 was intrinsic antiferroelectric phase, but the remanent polarization of induced-ferroelectric phase remained after electric-field was removed at room temperature.

Non-stoichiometric pyrochlore ceramics with formula Bi 1.5+ x ZnNb 1.5 O 7+1.5 x were systematically investigated. Crystal structures of the compounds were studied by X-ray diffraction (XRD) technique. The structures were identified as pure cubic pyrochlores when | x | x = −0.1, 0 and 0.1 were studied. All samples have high resistivities and low dielectric loss. With increasing x in Bi 1.5+ x ZnNb 1.5 O 7+1.5 x , the lattice constant, permittivity, temperature coefficient of permittivity and thermal expansion coefficient increased, while dielectric loss decreased. Raman spectra indicated that the intensity of Bi–O stretching become stronger with increasing x . A vibration mode emerging at 861 cm −1 when x = −0.1 means that the B–O coordination environment is significantly more disordered. Absorption spectra suggested that the bandgap energy become lower from 2.86 to 2.70 eV as lattice constants increased. Strong absorption occurs at wavelengths from 433 to 459 nm, shows that samples have the ability to respond to wavelengths in the visible light region.

(1 0 0)- and (1 0 1)-oriented PbTiO 3 (PT) thin films on conductive LaNiO 3 (LNO)-coated Si(1 1 1) substrates were prepared by a metal-organic decomposition method. It is found that the crystallization states of LNO thin films used as buffer layers have significantly effects on preferential orientation of PT thin films. PT thin films with (1 0 0) orientation could be obtained not only on the crystalline LNO (1 0 0) film, but also on the amorphous LNO thin film. The highly (1 0 0)-oriented PT films show high dielectric constant of 189.4 on LNO (1 0 0) films and 183.1 on amorphous LNO films. The PT capacitors fabricated on the LNO buffer layers display good P – E hysteresis loops. The remnant polarization ( P r ) and coercive field ( E c ) of PT films on amorphous, (1 0 0)- and (1 1 0)-oriented LNO films are 9.35 μC/cm 2 and 162.8 kV/cm, 10.03 μC/cm 2 and 163.3 kV/cm, 11.23 μC/cm 2 and 166.2 kV/cm, respectively.

The sintering behavior and dielectric properties of the monoclinic zirconolite-like structure compound Bi 2 (Zn 1/3 Nb 2/3 ) 2 O 7 (BZN) and Bi 2 (Zn 1/3 Nb 2/3− x V x ) 2 O 7 (BZNV, x = 0.001) sintered under air and N 2 atmosphere were investigated. The pure phase were obtained between 810 and 990 °C both for BZN and BZNV ceramics. The substitution of V 2 O 5 and N 2 atmosphere accelerated the densification of ceramics slightly. The influences on microwave dielectric properties from different atmosphere were discussed in this work. The best microwave properties of BZN ceramics were obtained at 900 °C under N 2 atmosphere with ɛ r = 76.1, Q = 850 and Q f = 3260 GHz while the best properties of BZNV ceramics were got at 930 °C under air atmosphere with ɛ r = 76.7, Q = 890 and Q f = 3580 GHz. The temperature coefficient of resonant frequency τ f was not obviously influenced by the different atmospheres. For BZN ceramics the τ f was −79.8 ppm/°C while τ f is −87.5 ppm/°C for BZNV ceramics.

Conductive perovskite lanthanum nickelate LaNiO 3 (LNO) thin films were fabricated on SiO 2 /Si substrates through metal-organic chemical liquid deposition method. The effect of annealing temperature on the orientation and sheet resistance of the LNO films were investigated. XRD patterns showed that the LNO films deposited on SiO 2 /Si substrates exhibited preferred-(1 1 0) orientation. The lowest sheet resistance of the LNO thin films, 250 Ω/□ was obtained after being annealed at 650 °C for 1 h. Subsequently, Pb 0.97 La 0.02 (Zr 0.85 Sn 0.13 Ti 0.02 )03 (PLZST) antiferroelectric thin films were prepared on the LaNiΟ 3 buffered SiO 2 /Si substrates via sol-gel process. And the crystallinity, microstructure and electric properties of the PLZST thin films were studied in details.

Metal–insulator–metal capacitors structures, employing the cubic pyrochlore Bi 1.5 Zn 1.0 Nb 1.5 O 7 (BZN) thick films, were fabricated by screen-printing techniques on alumina substrates. Chemical compatibility and microstructure between layers was studied by EDS/SEM analysis. The dielectric properties of BZN thick films have been investigated as a function of temperature and frequency. The films exhibited the dielectric constant up to 130, and the dielectric loss less than 0.005 at 1 MHz. The dielectric tunabilities of the films have been compared at different temperature. The BZN thick film showed low tunability of about 1.8% at 10 kHz under 100 kV/cm dc bias voltage in temperature from −150 to 180 °C. The temperature stability of dielectric properties for BZN thick film should be useful for designing temperature stable frequency agile.

Effect of substitution of CuO and WO 3 on the microwave dielectric properties of BiNbO 4 ceramics and the co-firing between ceramics and copper electrode were investigated. The (Bi 1-x Cu x )(Nb 1-x w x )O 4 (x = 0.005, 0.01, 0.015, 0.02) composition can be densified between 900 and 990 °C. The microwave dielectric constants lie between 36 and 45 and the pores in ceramics were found to be the main influence. The Q values changes between 1400 and 2900 with different x values and sintering temperatures while Q f values lie between 6000 and 16,000 GHz. The microwave dielectric losses, mainly affected by the grain size, pores, and the secondary phase, are discussed. The (Bi 1-x cu x )(Nb 1-x w x )O 4 ceramics and copper electrode was co-fired under N 2 atmosphere at 850 °C and the EDS analysis showed no reaction between the dielectrics and copper electrodes. This result presented the (Bi 1-x Cu x )(Nb 1-x W x )O 4 dielectric materials to be good candidates for LTCC applications with copper electrode.

ZnSe nanocrystals have been successfully synthesized by high energy ball milling method. X-ray diffraction patterns show a single zinc blende structure formed in the milling process. HRTEM images confirm that the formation of the ZnSe nanocrystals synthesized by high energy ball milling have a wide crystals distribution (3-20 nm). Using the aqueous solutions of Na 3 PO 4 , (NaPO 3 ) 6 and Na4P 2 O 7 to disperse the 40 h-milled samples, we have observed the gradual blue-shift of the absorption edge along with the different centrifuging speed. In PL spectras, two main bands peaked at about 1.95 and 2.35 eV are observed, the former band is related to the V Zn defects emission; and the latter is related to the V Se defects emission. The V Se defects emission does not depend on the dispersants, but the V Zn defects emission changes in different dispersants.