In-Situ Composition and Luminescence of Europium and Terbium Coordination Polymers/PEMA Hybrid Thick Films

Europium and terbium coordination polymers of pyridine-3-carboxylic acid were in-situ composed with ethyt methacrylate （ EMA ）. With the polymerization of EMA monomer and the formation of europium and terbium coordination polymers of pyridiae- 3-carboxylic acid, the transparent hybrid thick fihns composed of [ Eu（ NIC ）3 ]n （ [ Tb（ NIC）3 ]n ） and poly ethyl mettuwrylate （ PEMA ） have been prepared. The luminescence properties and energy transfer of these polymeric composites were studied with absorption spectra, fluorescent excitation trod emission spectra in detail. All the hybrid thick films composed of terbium coordination polymer show the characteristic strong green emission of terbium ions, which implies the same energy transfer mechanism as the pure complex and the hybrid composite film is a suitable sabstrate for the luminescence of terbium ions. In the range of camposing concentration of luminescent species （0.01,0.025,0.05,0.1 mmol /15 mL EMA ）, emission intensities increase with the increasing of corresponding composing concentration and the concentration quenching effect does not take place.

Enhanced ferro-/piezoelectric properties of tape-casting-derived Er^(3+)-doped Ba_(0.85)Ca_(0.15)Ti_(0.9)Zr_(0.1O3) optoelectronic thick films

Er^(3+)-doped Ba_(0.85)Ca_(0.15)Ti_(0.9)Zr_(0.1O3)(xEr-BCTZ,x=0,0.005,0.01,0.015)multifunctional thick films were prepared by the tape-casting method,using sol-gel-derived nano-sized powders as the matrix material.The surface morphologies,photoluminescence,and electrical properties were investigated.Dense microstructures with pure perovskite structure were obtained in the thick films.By doping an appropriate amount of Er^(3+),the samples exhibit superior up-conversion photoluminescence performance and simultaneously enhanced electrical performances.In addition,relatively higher texture fractions(with the largest value of 83.5%)were realized through introducing plate-like BaTiO_(3) templates to make the thick film grow by the[001]_(c) orientation.And the ferro-/piezoelectric properties of the thick films were further improved,showing potential in the applications of micro-optoelectronic devices.

PZT–NZF/CF ferrite flexible thick films:Structural,dielectric,ferroelectric,and magnetic characterization

The preparation and properties of thick flexible three-phase composite films based on lead zirconium titanate(PZT) and various ferrites(nickel zinc ferrite(NZF) and cobalt ferrite(CF)) were reported in this study. Properties of three-phase composite films were compared with pure polyvinylidene fluoride(PVDF) and PZT–PVDF films. X-ray diffraction data indicated the formation of well crystallized structure of PZT and NZF/CF phases, without the presence of undesirable phases. Scanning electron micrographs showed that the ceramic particles were dispersed homogeneously in the PVDF matrix and atomic force microscopy confirmed that the size of the particles is around 30 nm. Non-saturated hysteresis loops were evident in all samples due to the presence of highly conductive ferrite phases. Under magnetic field of 10 k Oe, composite films exhibited a typical ferromagnetic response. Dielectric properties were investigated in the temperature range from –128 to 250 ℃ and frequency range of 400 Hz–1 MHz. The results showed that the value of dielectric constant of the PVDF/PZT/ferrite composites increased about 25% above the one obtained for pure PVDF.

Investigation of low-temperature cathodoluminescence mechanism of Er-doped Ga N thick films by ion implantation

Er ions are implanted into the GaN thick films grown by hydride vapor phase epitaxy. The implantation energy is 200 keV and the implantation doses are 1 × 10^13, 1 × 10^14, 1 × 10^15, and 5 × 10^15 atom/cm2, respectively. The effects of the implantation dose and annealing temperature on the GaN band-edge luminescence are investigated. The cathodoluminescence spectra from 82 to 323 K are measured for 1 × 10^15 atom/cm2- implanted GaN annealed at 1100℃. Luminescence peaks at 356, 362, 376, 390, and 414 nm are observed on the 82 K cathodoluminescence spectrum. When the temperature is increased to 150 K, the intensities of the 356 and 414 nm peaks are nearly unchanged and the 362,376, and 390 nm peaks disappear. The intensity ratio of 538 nm （2H11/2 →4 4I15/2） and 559 nm （4A3/2 →4I15/2） is increased with the increase in temperature. We try to shed light on the above interesting phenomena.

Preparation and characterization of SiO_2/TiO_2/methylcellulose hybrid thick films for optical waveguides

SiO_2/TiO_2/methylcellulose composite materials processed by the sol-gel technique were studied for optical waveguide applications. With the help of methylcellulose, an organic binder, SiO2/TiO2/methylcellulose hybrid thick films were prepared by a single spin-coating processes. After annealing at 70 °C for an hour, 2.5-μm crack-free and dense organic-inorganic hybrid optical films with a refractive index of 1.537 were achieved. Optical losses of plane waveguide made up of those films and ordinary slide glass substrate are around 0.3 dB/cm at 650 nm. Scanning electronmicroscopy (SEM) and UV-visible spectroscopy (UV-VIS), have been used to characterize the thick films.

Stable self-polarization in lead-free Bi(Fe_(0.93)Mn_(0.05)Ti_(0.02))O_(3)thick films

The BiFeO3-based film is one of the most promising candidates for lead-free piezoelectric film devices.In this work,the 1μm-thick Bi(Fe_(0.93)Mn_(0.05)Ti_(0.02))O_(3)(BFMT)films are grown on the ITO/glass substrate using a sol-gel method combined with spin-coating and layer-by-layer annealing technique.These films display a large saturated polarization of 95μC/cm^(2),and a rema­nent polarization of 70μC/cm^(2).Especially,the films are self-poled caused by an internal bias field,giving rise to asymmetric polarization-electric field(P-E)loops with a positive shift along the x-axis.A stable self-polarization state is maintained during the applied electric field increasing to 1500 kV/cm and then decreasing back.The weak dependence of P-E loops on frequency(1-50 kHz)and temperature(25-125°C)indicate that the internal bias field can be stable within a certain frequency and tempera­ture range.These results demonstrate that the self-polarized BFMT thick films can be integrated into devices without any poling process,with promising applications in micro-electro-mechanical systems.

Effects of glass additions on energy storage performance of(Pb_(0.9)7La_(0.02))(Zr_(0.92)Sn_(0.05)Ti_(0.03))O_(3) antiferroelectric thick films

50μm-thick(Pb_(0.9)7La_(0.02))(Zr_(0.92)Sn_(0.05)Ti_(0.03))O_(3) antiferroelectric(AFE)thick films with different amount of 0.8Pb_O-0.2B_(2)O_(3) glass additions were fabricated by the screen-printing method on alumina substrate,which was pre-coated with Pt as electrode.The effects of glass additions on dielectric properties and energy storage performance were investigated in details.Due to the enhancement of breakdown strength(BDS)of the specimens by the addition of glass,the energy storage performances of the thick films could be greatly improved.As a result,with 3%glass addition,the BDS of the specimens were as high as 475 kV/cm,the maximum polarization of 34.8μC/cm^(2) and the maximum recoverable energy storage density of 7.4 J/cm^(3) were obtained.The results indicated the(Pb_(0.9)7La_(0.02))(Zr_(0.92)Sn_(0.05)Ti_(0.03))O_(3) (PLZST)thick films have a promising potential application in capacitors for pulsed power systems.

Texture and self-biased property of an oriented M-type barium ferrite thick film by tape casting

In this paper, the oriented M-type barium ferrite （BaM） thick films with different thicknesses are prepared by tape casting. It is found that the crystallographic alignment degree （f）, the pore and the squareness ratio （Mr/Ms） are not affected by the thickness of the film. XRD and SEM results show that the thick film has hexagonal morphology with a crystal texture of c-axis grains perpendicular to film plane. The hysteresis curve indicates that the BaM thick film exhibits a self-biased property with a remanent magnetization of 3.30 T, a squareness ratio （Mr/Ms） of 0.81, and a coercivity of 0.40 T. The results show that the BaM thick film has potential for use in self-biasing microwave devices, and also proves that the tape casting technique is capable of fabricating high-quality barium ferrite films, thus providing a unique opportunity to realize the large area production of thick film.

Femtosecond laser induced index and relief gratings in polymer films

A true single-step process suitable for fabrication of micro-periodic structure in polymer films by twophoton initiated photopolymerization and laser ablation is presented. By the right choice of the irradiation energy, the irradiated zone is modified or ablated in the 1.44-μm-thick film. The mechanism of grating generation and the potential application of the gratings in integrated optics are discussed.

Intrinsic ZnO films fabricated by DC sputtering from oxygen-deficient targets for Cu(In,Ga)Se_2 solar cell application

Intrinsic zinc oxide films, normally deposited by radio frequency （RF） sputtering, are fabricated by direct current （DC） sputtering. The oxygen-deficient targets are prepared via a newly developed double crucible method. The 800-nm-thick film obtaines significantly higher carrier mobility compareing with that of the 800-nm-thick ZnO film. This is achieved by the widely used RF sputtering, which favors the prevention of carrier recombination at the interfaces and reduction of the series resistance of solar cells. The optimal ZnO film is used in a Cu （ln, Ga） Se2 （CIGS） solar cell with a high efficiency of 11.57%. This letter demonstrates that the insulating ZnO films can be deposited by DC sputtering from oxygen-deficient ZnO targets to lower the cost of thin film solar cells.

Temperature-dependent dielectric anomalies in powder aerosol deposited ferroelectric ceramic films

Room-temperature fabrication of functional ceramic films using powder aerosol deposition(AD)is important for practical applications.However,the as-processed ferroelectric films show unusual temperature-dependent dielectric response,including enhanced conductivity in the as-processed state and subsequent significant increase in the permittivity following heat treatment.In this work,we investigate the influence of the residual internal stresses developed during the high-impact consolidation process on the dielectric response.Moreover,the recombination of charged defects generated during deposition is driven by the temperature and the atmospheric condition during the heat treatment as well as the carrier gas type used during deposition.Thermal treatment up to 500℃ in different atmospheres was used to tune the dielectric and ferroelectric response,highlighting that irrespective of the type of carrier gas,AD deposition process induces charged defects in polar oxide ceramics that can be reduced through heat-treatment far-below their bulk sintering temperature.Macroscopic electromechanical properties are contrasted to in-situ heating scanning transmission electron microscopy to observe possible local effects,such as crystallization,grain growth,crystal defect structure,or grain reorientation.In addition X-ray diffraction and X-ray photoelectron spectroscopy studies were conducted to gain insight into the effect of annealing on the crystal structure and local moisture adsorption.

Electrical properties of BaFe_(0.9)Sn_(0.1)O_(3)–BaCo_(0.02)^(Ⅱ)Co_(0.04)^(Ⅲ)Bi_(0.94)O_(3)composite thick-film thermistors

The BaFe_(0.9)Sn_(0.1)O_(3)-BaCo_(0.02)^(Ⅱ)Co_(0.04)^(Ⅲ)Bi_(0.94)O_(3)composite thick films were prepared by screen printing.X-ray diffraction(XRD)analysis confirms that the composite films are still composed of BaFe_(0.9)Sn_(0.1)O_(3)-BaCo_(0.02)^(Ⅱ)Co_(0.04)^(Ⅲ)Bi_(0.94)O_(3)phases.For the prepared BaFe_(0.9)Sn_(0.1)O_(3)-BaCo_(0.02)^(Ⅱ)Co_(0.04)^(Ⅲ)Bi_(0.94)O_(3)composite thick films,a linear relationship between the logarithmic resistivity and the reciprocal of the absolute temperature is observed,indicating an excellent NTC thermistor characteristic.The values of resistivity at 25℃,thermistor constant and activation energy,decreasing with BaCo_(0.02)^(Ⅱ)Co_(0.04)^(Ⅲ)Bi_(0.94)O_(3)content increasing,are in the range of 8.9-92,990Ω·cm,1,126-3,777 K and 0.097-0.325 eV,respectively.Impedance analysis shows that at higher BaCo_(0.02)^(Ⅱ)Co_(0.04)^(Ⅲ)Bi_(0.94)O_(3)content,the electrical properties of the composite films are mainly attributed to the contribution of grains and grain boundaries.With the gradual decrease of BaCo_(0.02)^(Ⅱ)Co_(0.04)^(Ⅲ)Bi_(0.94)O_(3)content,the grain boundaries affect strongly the electrical properties of the composite films.

Ultrafast thermoelasticity modeling of microbump formation irradiated by femtosecond laser

Finite element method and ultrafast thermoelasticity model are combined to simulate the microbump formation irradiated by a femtosecond laser. It has been shown that the effect of microbump formation is related to the characteristic of incident femtosecond laser and the thermoelasticity properties of the film. The numerical results exhibit good agreements with the experimental results in both the shape and height of the conical microbump structure, which verify the effectiveness of the ultrafast thermoelasticity model in experiments. It should be helpful for selecting appropriate materials for nanotexturing of thin films by ultrafast lasers.

Near-Net-Shaped Objects of RE123 Superconductors byInfiltration Processing

The fabrication of near-net-shaped objects of RE123 superconductors by 'infiltration processing' is discussed. Near-net-shape processing involves the infiltration of preshaped porous green bodies of either 211 or yttria phases by liquids containing barium cuprates and copper oxides followed by a controlled peritectic solidification. The process yields poly- and also single-crystalline superconducting objects with a shrinkage of less than half of one percent of the green bodies. The preservation of the initial structure of the green bodies results in fabrication of RE 123 in a wide variety of dimensions and complex shapes. The demonstrated products include bulk components like cylinders, single domain thick films on a variety of substrates, freestanding fabrics and open porous superconducting foams. This paper presents a comprehensive description of the infiltration processing technique and the resulting microstructures of the superconducting bodies. The advantages of this technique and practical applications of the processed superconducting structures are highlighted.