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A magnetostrictive-piezoelectric laminated composite has been developed by sandwiching a lead-free BNKLBT ceramic plate polarized in the thickness direction between two terfenol-D continuous fiber composite plates. This lead-free magnetoelectric (ME) laminated composite has a large ME voltage sensitivity of 2.5 V/Oe at the resonance frequency of 130.9 kHz under a low magnetic bias field (HBias) of 0.6 kOe. This work shows the potential of BNKLBT lead-free ceramics in ME sensing application. [ABSTRACT FROM AUTHOR]

The use of lead-free materials has recently become a very important issue in environmental protection of the earth. Two groups of lead-free ceramics, (K0.5,Na0.5)NbO3 based (KNN) and Bi1-y(NaxK1-x)yTiO3 based (BNKT), were studied for their thermal, dielectric, and pyroelectric properties as candidates for pyroelectric sensor applications. The BNKT-based ceramic, [Bi0.5(Na0.94K0.05Li0.016)0.5]0.95Ba0.05TiO3 (BNKLBT), shows excellent pyroelectric properties when compared with KNN-based ceramic and lead zirconate titanate. Its properties were measured as follows: pyroelectric coefficient p=360 μC/m2 K, pyroelectric figure of merit of current, voltage, and detectivity Fi=221 pm/V, Fv=0.030 m2/C, and Fd=14.8 μPa-1/2. With these outstanding pyroelectric properties, the BNKLBT ceramic can be a promising material for pyroelectric sensor applications. The BNKLBT ceramic with different thicknesses (i.e., 0.3, 0.5, and 0.7 mm) have been used as the sensing element for fabricating infrared detectors. The current responsivity of the sensors was evaluated as functions of frequency. [ABSTRACT FROM AUTHOR]

Bismuth sodium titanate based lead-free ceramic fiber with the chemical formula of 0.885(Bi0.5Na0.5)TiO3–0.05(Bi0.5K0.5)TiO3–0.015(Bi0.5Li0.5)TiO3–0.05BaTiO3, BNKLBT-1.5, has been fabricated by a powder-based extrusion method. The ceramic fibers with 400 μm diameter were well crystallized after being calcined at 800 °C and sintered at 1170 °C. The piezoelectric and ferroelectric properties of the single fiber were found to be 155 pC/N and ∼34.5 μC/cm2, respectively, which is comparable with that in bulk sample. 1-3 ceramic/polymer composites were fabricated by two routes, including dice and filled method and fiber pick-and-place method. Theoretical models were used to calculate the piezoelectric properties of the composites and compared with experimental results. [ABSTRACT FROM AUTHOR]

(0.95-x)(Bi1/2Na1/2)TiO3-x(Bi1/2K1/2)TiO3-0.05BaTiO3 lead-free piezoelectric ceramics sabbreviated as BNT-BKT-BT100x with x varying from 0 to 20 mol %d are prepared by a solid-state reaction process. Variation of the dielectric properties and microstructure of BNT-BKT-BT100x ceramics with BKT content is studied. The results indicate that the relative permittivity εr and loss tangent tan d vary with the BKT amount. Scanning electron microscope observation also indicates that BKT in high amount affects the microstructure. X-ray diffraction analysis shows that the incorporated BKT diffuses into the BNT-BT lattice toform a solid solution during sintering. [ABSTRACT FROM AUTHOR]

Lead-free (0.90-x)(Bi1/2Na1/2)TiO3-0.05(Bi1/2K1/2)TiO3-x(Bi1/2Li1/2)TiO3-0.05BaTiO3 piezoelectric ceramics (abbreviated as BNKLBT-100x, with x ranged from 0 to 2.5 mol %) were prepared by a conventional mixed oxide method. Effects of the amount of (Bi1/2Li1/2)TiO3 (BLT) on the electrical properties and crystal structure of the BNKLBT ceramics were examined. BNKLBT-1.5 ceramics have good properties with piezoelectric constant d33=163 pC/N, electromechanical coupling factor kp=0.33, kt=0.53, relative permittivity εr=785 and dissipation factor cosδ=2.2% at 1 kHz. The sample has larger remnant polarization than BNKLBT-0 ceramics and the same coercive field as BNKLBT-0 ceramics. X-ray diffraction analysis shows that the incorporated BLT diffuses into the BNT–BKT–BT lattice to form a solid solution during sintering, but changes the crystal structure from rhombohedral to tetragonal symmetry at higher BLT amounts. Depolarization temperature (Td) of the BNKLBT-100x ceramics increases from 102 °C to ∼136 °C for BNKLBT-0 to BNKLBT-2.5. BNKLBT-1.5 is used as the transduction element in compressive type accelerometer and its sensitivity is calibrated by the back-to back method. Within the ±2.5% tolerance, the lead-free accelerometer has a mean value of 2.97 pC/ms-2 within 50 Hz–12.45 kHz and the lead-based accelerometer has a mean value of 4.34 pC/ms-2 within 50 Hz to 8.24 kHz. [ABSTRACT FROM AUTHOR]

Lead-free bismuth sodium potassium lithium titanate - barium titanate [0.885 (Bi1/2Na1/2)TiO3-0.05(Bi1/2K1/2)TiO3-0.015(Bi1/2Li1/2)TiO3-0.05BaTiO3, BNKLBT-1.5] fibres have been fabricated by a powder-based extrusion method. The ceramic fibres with 400 μ m diameter were well-crystallized after being calcined at 800°C and sintered at 1170°C. After being poled, the electromechanical coupling coefficient k33 of the fibre is 0.55 while other properties are comparable to those a ceramic disc. The BNKLNT ceramic fibres prepared by the powder-based extrusion method have good piezoelectric and ferroelectric properties and have potential to replace lead zirconate titanate (PZT) fibres in various device applications. [ABSTRACT FROM AUTHOR]

This paper presents a stepped horn transducer based on lead-free piezoelectric ceramics. A two-step titanium horn has been bonded to a Ba0.95Ti0.95Sr0.05Zr0.05O3 (BSZT) lead-free piezoelectric ceramic disk. The stepped horn is a promising candidate for transducer design mainly due to its efficacious mechanical amplification. The strontium and zirconium doped barium titanate has been prepared in disk-shape and poled in a thickness direction. When an AC voltage is applied to the electrodes of the driving disk, the lead-free piezoceramic disk produces radial ultrasonic contractions and expansions. The stepped horn transforms and amplifies the radial deformation into an axial vibration of the horn tip. At resonance, the deformation of the horn is significantly enhanced, the axial displacement of the horn tip has been measured near the resonance frequency and compared to that produced by a PZT driven transducer. Finite element modeling has been conducted to determine the vibration mode and resonance frequency of the device. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramic 0.90(Bi1/2Na1/2)TiO3–0.05(Bi1/2K1/2)TiO3–0.05BaTiO3 (BNKBT-5) rings (OD=12.7 mm, ID=5.1 mm and 2.3-mm thick) were fabricated and characterized. Four ceramic rings were used as the driving element in an ultrasonic wirebonding transducer and the performance of the transducer was characterized. The lead-free transducer was found to have comparable voltage rise and fall times as a lead-based PZT transducer and has a relatively large vibration amplitude, thus showing that BNKBT-5 has the potential to be used in fabricating lead-free ultrasonic wirebonding transducers. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric 0.75(Bi 1/2 Na 1/2 )TiO 3 -0.20(Bi 1/2 K 1/2 )TiO 3 -0.05BaTiO 3 ceramics(abbreviated as BNKBT-20) with addition of 0.2, 0.4, 0.6 and 0.8 wt% of CeO 2 , respectively, were prepared by a conventional mixed oxide method. The addition of CeO 2 can reduce the dissipation factor and enhance the mechanical quality factor significantly. The composition with 0.4 wt% CeO 2 has a piezoelectric d 33 constant of 129 × 10 - 12 C/N and a relatively low dissipation factor (tan δ = 1.8%) at 1 kHz which shows a 50% reduction in the dissipation factor when compared with BNKBT-20 before doping (tan δ = 3.74%). [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric 0.90(Bi1/2Na1/2)TiO3-0.05(Bi1/2K1/2)TiO3-0.05BaTiO3 ceramics(abbreviated as BNKBT-5) rings were fabricated using a conventional mixed oxide method. The ceramics have a piezoelectric constant d33=168 pC/N, electromechanical coupling factors kp=0.313 and kt=0.487. The BNKBT lead-free ceramic rings were used as the transduction elements in a compressive type accelerometer and its performance compared with a lead zirconate titanate (PZT) APC 840 ceramic accelerometer with similar structure. The lead-free accelerometer shows good performance and has a broader frequency response compared to the lead-based PZT accelerometer. [ABSTRACT FROM AUTHOR]

Lead zirconate titanate (PZT) fibres were prepared by a powder-based extrusion method. Pre-sintered PZT powder mixed with poly(acrylic acid) was spun in a spinnerette to produce fibres. The fibre of ∼400 μm diameter was used to fabricate 1-3 PZT fibre/epoxy composite discs with different volume fractions (ϕ) of PZT. Since the ceramic fibres are rather brittle, their elastic properties cannot be measured directly. In order to determine the properties of the ceramic fibres, effective properties of the fibres/epoxy 1-3 composite were measured. By using a modified series and parallel model, the properties of 1-3 composites can be calculated. Then, the elastic coefficient s33,fibreE, relative permittivity ε33,fibreT and piezoelectric strain coefficient d33,fibre of the ceramic fibre could be found. Ring-shaped PZT fibre/epoxy materials composites with different ϕ were fabricated to be used as the sensing material in force sensor applications. The ring-shape composite with ϕ=0.5 was installed into a housing and the sensor was calibrated by different methods and its sensitivity was found to be 144 pC/N within the frequency range of 0.5–6.4 kHz which is much higher than that of a quartz force sensor with a similar structure. [ABSTRACT FROM AUTHOR]

Doping effects with respect to the electrical properties of morphotropic phase boundary (Bi0.5Na0.5)0.94Ba0.06TiO3 thin films epitaxially grown on CaRuO3 electroded (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) substrates were investigated. Substantial enhancement of ferroelectricity and piezoelectricity has been achieved in La+Ce codoped films with a remanent polarization Pr of 29.5 μC/cm2 and a remanent piezoelectric coefficient d33,f of 31 pm/V, whereas Mn doping seems more favorite to reduce the leakage current by two order of magnitude. Both doped films exhibited diodelike I-V characteristics, which are correlated with resistance switching effect. [ABSTRACT FROM AUTHOR]

Thermal tuning of phononic bandgaps in megahertz range was demonstrated in ferroelectric ceramic-based phononic crystal structure. Temperature variation across ferroelectric phase transition, accompanied by substantial changes in acoustic velocities, leads to a shift in the phononic bandstructure of a two-dimensional (Ba,Sr)TiO3/epoxy composite sample over a range of 10 °C. Experimental results are supported by modelings based on plane-wave expansion calculations. The high tunability of phononic bandstructure is advantageous for active control of ultrasound transmissions. [ABSTRACT FROM AUTHOR]

A high sensitivity piezoelectric accelerometer has been developed by replacing the conventional piezoelectric rings with a cymbal transducer. The sensitivity of the cymbal-based accelerometers containing cymbal transducers with different endcap thicknesses and different seismic masses has been measured as a function of driving frequency. Due to the high d33′ coefficient of the cymbal transducers, the cymbal-based accelerometers have a high sensitivity of ∼97 pC/ms-2 with the amplitude rise of 2.85% (<1 dB) at one-third of the mounted resonance frequency (3.38 kHz). The effect of the seismic mass, the resonance frequency, and d33′ coefficient of the cymbal transducers on the sensitivity and the frequency range of the cymbal-based accelerometers are reported. [ABSTRACT FROM AUTHOR]

A correction to the article "Lead free ceramics for pyroelectric applications" published online on December 18, 2008 is presented.

An unusual case of cavernous hemangioma of the superior mediastinum in a 38-year-old male is presented. Mediastinal hemangiomas occur more often in children and are usually localized in the anterior-superior compartment in all age groups. Slow expansile growth, lack of infiltration of adjacent structures and microscopically mature cellular elements clearly marked the benign nature of the lesion. Vascular mesenchymal tumors in this location must be approached with caution because of the risks of hemorrhage or local infiltration of vital structures. Electron microscopy revealed active endothelial cells, smooth muscle cells, and intercellular matrix components suggestive of smooth muscle cell origin. Computerized tomography delineated the lesion clearly and demonstrated identical densities for the mass and adjacent blood vessels.

The formation of structures resembling hair matrices is the least common form of follicular differentiation and only occurs with any frequency in pilomatricoma. Rarely, follicular cysts and both benign and malignant adnexal tumors can show areas of pilomatricoma-like change, or hair matrix differentiation. Examples of focal hair matrix differentiation in a follicular cyst, a cutaneous mixed tumor, and an adnexal carcinoma are presented. Each of these cases also demonstrates the presence of limited differentiation toward structures of the inner root sheath.