Analysis of characteristics of broadband matching for piezoelectric ceramic transducer

Characteristics of broadband matching for piezoelectric ceramic transducer are fully analyzed. It is stated that in the case of without an all pass function, good matching characteristics of maximum bandwidth and gain-bandwidth product are implied in the Butterworth matching theorem. If the parameterσ< .252, it is not helpful to add an all pass function to the circuit following the rule of minimizing center frequency and maximizing gain-bandwidth product.     

Laser-induced chemical etching of ceramic PbTi1−xZrxO3

The laser-induced etching of ceramic PbTi_1–xZr_xO₃ in a hydrogen atmosphere and in air has been investigated. Visible Ar⁺ and Kr⁺ laser radiation was employed in most of the experiments. In H₂ atmosphere, regular patterning of the ceramic is possible. Average etch rates reach up to about 250 m/s.     

Parallel ripple formation during femtosecond laser grooving of ceramic

The self-organized formation of ripples in the direction parallel to the groove during the femtosecond laser machining of microgrooves on aluminum nitride ceramic at laser fluences much higher than the single-pulse ablation threshold is reported. These parallel ripples are notably different from the commonly observed polarization-perpendicular ripples and are produced in grooves having an appropriate width and depth, irrespective of laser polarization. From subsequent experiments with narrow and wide groove widths, it could be considered that the groove walls play an important role in the formation of these parallel ripples, possibly by confining the laser-induced plasma.     

Comparison of laser performance of electro-optic Q-switched Nd:YAG ceramic/single crystal laser

An electro-optic Q-switched Nd:YAG ceramic laser operating at kHz repetition rate was demonstrated. Thermal induced lens' focus of ceramic rod was measured and compensated by plano-convex cavity structure. Depolarization loss at different output powers was measured in Nd:YAG single crystal and ceramic lasers. High-energy high-beam-quality laser pulse output was obtained in both laser structures. Pulse energy of about 20 mJ and pulse width of less than 12 ns were achieved, and the average power reached 20 W. The divergence of output laser beam was less than 1.2 mrad, and the beam propagation factor M2 was about 1.4.     

Investigation of emission properties of Tm3＋：Y2O3 transparent ceramic

A transparent and emitting ceramic of Y 2 O 3 doped with 6% Tm 3+ ions is fabricated by vacuum sintering with ZrO 2 . Absorption, photoluminescence (PL), and PL excitation (PLE) spectra are investigated in a spectral range of 200 to 2 100 nm at various temperatures between 296 and 12 K. Intense emission band appears at 450 to 465 nm in the visible range. Near-infrared emission bands are observed at 1 200 to 1 300 nm and 1 400 to 1 550 nm, with intense peaks at 1 270, 1 450, and 1 523 nm. The luminescence mechanisms and potential applications of the emissions are discussed with the help of Judd-Ofelt theory and PLE spectra.     

Study of an anisotropic ferrimagnetic bioactive glass ceramic for cancer treatment

For the hyperthermia therapy of cancer, ferrimagnetic glass ceramics are a potential candidate. Ferrimagnetic zinc-ferrite-containing bioactive glass ceramics were prepared by quenching the glass ceramics from sintering temperature. Then the samples were heated to 600°C and cooled in an aligning magnetic field of 1 Tesla to cause anisotropy. The magnetically aligned samples were compared with non-aligned samples. Vibrating sample magnetometry measurements at 10 kOe showed that the magnetic properties were enhanced by the aligning magnetic field and it led to an enhancement of the magnetic heat generation under a magnetic induction furnace operating at 500 Oe and 400 kHz for 2 min. Data showed that the maximum specific power loss and temperature increase after 2 min were 31.5 W/g and 45°C, respectively, for the aligned sample of maximum zinc-ferrite crystalline content. The glass ceramics were immersed in simulated body fluid for 3 weeks. X-ray diffraction and Fourier transform infrared and atomic absorption spectroscopy results indicated the growth of precipitated hydroxyapatite, suggesting that the ferrimagnetic glass ceramics were bioactive and could bond to living tissues in physiological environment.     

Raman spectroscopic study of ceramic Sr2Bi4Ti5O18

Raman spectra of ceramic Sr2Bi4Ti5O18 （SBTi5） are reported to consist of four different Raman bands. Temperature-dependent spectra reveal the relationship between the lattice vibration and the material＇s structure. There appears a relatively large change in structure of the material at about 273K, The anharmonic potential of the material has a great influence on its phonon mode full width at half maximum （FWHM）, which can be expressed by a function of temperature. Theoretical fittings of the FWHMs for the two modes at around 312 cm^-1 and 464cm^-1 indicate that the latter phonon mode is more anharmonic than the former one.     

A model for “cold” laser ablation of green state ceramic materials

This paper reports calculations of predicted values of the key process parameters associated with “cold” laser ablation of ceramic materials in the green state. A model for material removal of composite organic/ceramic materials is proposed and verified experimentally by laser ablation measurements and ultrafast videography. An energy balance approach is used with the model to calculate values of threshold fluence, material removal rate and particle escape velocity, which are seen to be in good agreement with experimental results. Suggested values for optimised laser machining of LTCC are proposed. PACS 79.20.Ds; 42.62.Cf; 42.55.Lt; 81.20.Wk     

Phase formation and electrical properties of BNLT–BZT lead-free piezoelectric ceramic system

Phase formation study in lead-free piezoelectric ceramics based on lanthanum doped bismuth sodium titanate (Bi_0.4871Na_0.4871La_0.0172TiO₃:BNLT) and zirconium doped barium titanate (BaZr_0.05Ti_0.95O₃:BZT), has been carried out in the system of (1−x)BNLT–xBZT where x = 0.0–1.0, by two-step mixed oxide method. It was observed that the addition of BZT in the BNLT ceramics developed the dielectric and piezoelectric properties of the ceramics with the optimum piezoelectric constant (d₃₃) and dielectric constant (ε_r) at room temperature of about 138 pC/N and 1651, respectively, from the 0.2 BNLT to 0.8 BZT ceramic sample. The Curie temperature (T_C) of this ceramic was found at 295 °C which is 195 °C higher than that of pure BZT ceramics, promising the use of this ceramic in a higher range of temperature.     

Effect of electric field,stress and environment on delayed fracture of a PZT-5 ferroelectric ceramic

The combined effect of electric and mechanical loading on fracture of a PZT-5 ferroelectric ceramic in silicone oil has been investigated using a single edge notched specimen. The results show that the fracture toughness and the threshold stress intensity factor of delayed fracture in silicone oil, i.e. stress corrosion cracking, decrease linearly with the increasing applied electric field, either positive or negative. For the PZT-5 ferroelectric ceramics, delayed fracture in silicone oil under sustained positive or negative field can occur, and the threshold field for delayed fracture under sustained positive or negative field decreases linearly with applied stress intensity factor. The combined effect of electric and mechanical loading on delayed fracture in silicone oil includes field-enhancing delayed fracture under sustained load and stress-enhancing delayed fracture in silicone oil under sustained field.     

Study of the crystalline structure of the superconducting phase of the YBaCuO ceramic compound

We present the results of a study of the crystalline structure of the high-temperature superconducting (above 110K) phase in the single-phase ceramic compounds YBaCuO. We have concluded that the crystal symmetry of this HTS phase with chemical composition Y_1.2Ba_0.8CuO_4−δ is orthorhombic type with crystallographic lattice constants a=0.3815 nm, b=0.3457 nm, c=2.650 nm.     

Optical and structural properties of Zn1−x Mg x O ceramic materials

This paper reports structural, optical and cathodoluminescence characterizations of sintered Zn_1?x Mg _x O composite materials. The effects of MgO composition on these film properties have been analyzed. X-ray diffraction (XRD) confirms that all composites are polycrystalline with prominent hexagonal wurtzite structure along two preferred orientations (002) and (101) for the crystallite growth. Above doping content x = 10 %, the formation of the hexagonal ZnMgO alloy phase and the segregation of the cubic MgO phase start. From reflectance and absorption measurements, we determined the band gap energy which tends to increase from 3.287 to 3.827 eV as the doping content increases. This widening of the optical band gap is explained by the Burstein–Moss effect which causes a significant increase of electron concentration (2.89 × 10¹⁸?5.19 × 10²⁰ cm^?3). The luminescent properties of the Zn_1?x Mg _x O pellets are studied by cathodoluminescence (CL) at room and liquid nitrogen temperatures under different electron beam excitations. At room temperature, the CL spectra of the Zn_1?x Mg _x O composites exhibit a dominant broad yellow-green light band at 2.38 eV and two ultraviolet emission peaks at 3.24 and 3.45 eV corresponding to the luminescence of the hexagonal ZnO and ZnMgO structures, respectively. For the doped ZnO samples, it reveals also new red peaks at 1.72 and 1.77 eV assigned to impurities’ emissions. However, the CL spectra recorded at 77 K show the presence of excitonic emission peaks related to recombination of free exciton (X _A), neutral donor-bound excitons (D⁰X) and their phonon replicas. The CL intensity and energy position of the green, red and ultraviolet emission peaks are found to depend strongly on the MgO doping content. The CL intensity of the UV and red emissions is more enhanced than the green light when the MgO content increases. CL imaging analysis shows that the repartition of the emitting centers in Zn_1?x Mg _x O composites is intimately connected to the film composition and surface morphology.     

Light scattering and 2-μm laser performance of Tm:YAG ceramic

The scattering effect of Tm:YAG ceramic has been investigated and the scattering coefficient at 1064 nm wavelength is measured to be 0.014 cm⁻¹. Furthermore, a high power Tm:YAG ceramic laser with a slope efficiency of 10.7% has been built, which is end-pumped at a central wavelength of 805 nm. The 2-μm maximum output power is 7.1 W with an optical-optical conversion efficiency of 7.2%.     

Release of charges under external fields of PbLa（Zr,Sn,Ti）03 ceramic＊

This paper investigates the pyroelectric of poled antiferroelectric （AFE） ceramic Pbo.97Lao.02 （Zro.69Sno.196 Ti0.114）03 and its remnant polarization dependence of hydrostatic pressure. The results show that the bound charges of poled sample can be released in short time by temperature field or pressure field. The released charge abruptly forms a large pulse current. The phenomena of released charge under external fields result in the ferroelectric-AFE phase transition induced by temperature or hydrostatic pressure.     

Effect of additives on structure and corrosion resistance of ceramic coatings on Mg–Li alloy by micro-arc oxidation

In order to improve the corrosion resistance of ceramic coatings formed on Mg–5mass%Li substrate by micro-arc oxidation (MAO) method, two kinds of additives (Na₂B₄O₇ and EDTA) were doped in Na₂SiO₃–Na₃PO₄ solution system. The surface and cross-section morphology feature, phase composition and elemental composition were examined by SEM, XRD and EDX, respectively. Corrosion resistance of ceramic coating was tested by electrochemical methods. It was revealed that all coatings were composed of MgO and Mg₂SiO₄, and had porous surface structure. Doping of additives had little effect on the elemental composition, while it influenced the morphological feature of the coating. The results of electrochemical tests showed that the coatings prepared in the solutions with additive had good corrosion resistance. The addition of EDTA to the solution made coatings thinner and more uniform which resulted in better general corrosion resistance. The addition of Na₂B₄O₇ to the solution made coatings much thicker and compacter, which improved the pitting corrosion resistance.     

Fabrication of ceramic oxide-coated SWNT composites by sol–gel process with a polymer glue

The functional copolymer bearing alkoxysilyl and pyrene groups, poly[3-(triethoxysilyl)propyl methacrylate]-co-[(1-pyrene-methyl) methacrylate] (TEPM₁₃-co-PyMMA₃), was synthesized via atom transfer radical polymerization. Attributing the π–π interaction of pyrene units with the walls of single-walled carbon nanotubes (SWNTs), this polymer could disperse and exfoliate SWNTs in different solvents through physical interaction as demonstrated by TEM, UV/Vis absorption, and FT-IR analysis. The alkoxysilyl groups functionalized SWNTs were reacted with different inorganic precursors via sol–gel reaction, and, as a results, silica, titania, and alumina were coated onto the surface of SWNTs, respectively via copolymers as a molecular glue. The nanocomposites of ceramic oxides/SWNTs were characterized by SEM analysis. Dependent upon the feed, the thickness of inorganic coating can be tuned easily. This study supplies a facile and general way to coat SWNTs with ceramic oxides without deteriorating the properties of pristine SWNTs.     

Electrical properties of ferroelectric BiMnO3–PbTiO3 under tailored synthesis and ceramic processing

Conductivity is a main issue in research on multiferroic perovskite oxides, which makes the characterization of their ferroelectric properties difficult, and for several compounds even to unambiguously state their ferroelectric nature. In this report, we use ferroelectric BiMnO₃–PbTiO₃ as a model system to study the relationships among synthesis, processing, and conductivity in ABO₃ perovskite oxides with magnetically active cations in the B-site. Three single phase, dense ceramic materials processed by conventional sintering, hot pressing, or spark plasma sintering (SPS) of powders synthesized by either wet chemistry or mechanochemical activation were studied. Impedance spectroscopy analysis was carried out to obtain grain and grain boundary conductivities for the three materials, along with activation energies. Mechanosynthesis is shown not to modify the mechanism of bulk or boundary conductivity, but only the carrier concentration, while SPS processing results in a low temperature, additional conduction mechanism.     

Microstructure of pulsed laser deposited ceramic–metal and polymer–metal nanocomposite thin films

Ceramic–metal (MgO combined with Fe, Ti and Ni₈₀Nb₂₀) and polymer–metal (polycarbonate combined with Ag and Pd) nanocomposite multilayers were deposited at room temperature by laser ablation (at 248 nm). The multilayers were characterized by X-ray reflectometry, infrared spectroscopy and transmission electron microscopy. In the case of MgO/metal multilayers, well-layered structures are produced down to layer periodicities of 1.2 nm, necessary for tunneling magnetoresistance devices and X-ray mirrors in the water window. The interface roughness in the case of polymer/metal multilayers is found to be a strong function of the metal layer thickness and also the nature of the metal. PACS 68.55.-a; 81.15.Fg