Crystallographic texturing of polycrystalline ferroelectric ceramics offers a means of achieving significant enhancements in the piezoelectric response. Templated grain growth (TGG) enables the fabrication of textured ceramics with single crystal-like properties, as well as single crystals. In TGG, nucleation and growth of the desired crystal on aligned single crystal template particles results in an increased fraction of oriented material with heating. To facilitate alignment during forming, template particles must be anisometric in shape. To serve as the preferred sites for epitaxy and subsequent oriented growth of the matrix, the template particles need to be single crystal and chemically stable up to the growth temperature. Besides templating the growth process, the template particles may also serve as seed sites for phase formation of a reactive matrix. This process, referred to as Reactive TGG (RTGG), has been used to obtain highly oriented Pb(Mg1/3Nb2/3)O3-PbTiO3, Sr0.53Ba0.47Nb2O6, and (N...

Templated Grain Growth of Textured Piezoelectric Ceramics

Nanorods, nanowires, and nanotubes of ferroelectric perovskites have recently been studied with increasing intensity due to their potential use in non-volatile ferroelectric random access memory, nano-electromechanical systems, energy-harvesting devices, advanced sensors, and in photocatalysis. This Review summarizes the current status of these 1D nanostructures and gives a critical overview of synthesis routes with emphasis on chemical methods. The ferroelectric and piezoelectric properties of the 1D nanostructures are discussed and possible applications are highlighted. Finally, prospects for future research within this field are outlined.

One-dimensional nanostructures of ferroelectric perovskites.

Review of the biocompatibility of micro-arc oxidation coated titanium alloys

Integral passives are becoming increasingly important in realizing next generation electronics industry needs through gradual replacement of discretes. The need for integral passives emerges from the increasing consumer demand for product miniaturization thus requiring components to be smaller and packaging to be space efficient. In this paper, the feasibility of integration of polymer/ceramic thin film (∼5 μm thick) capacitors (C) with other passive components such as resistors (R) and inductors (L) has been discussed. An integrated RC network requiring relatively large capacitance and resistance is selected as a model for co-integration of R and C components using low temperature PWB compatible fabrication processes. This test vehicle is a subset of a large electrical circuit of a functional medical device. In order to produce higher capacitance density and reduce in-plane device area, multi-layer (currently two-layer) capacitors are stacked in the thickness direction. A commercially available Ohmega-Ply resistor/conductor material is selected for integral resistors. Resistors were fabricated using a multi-step lithography process with the utilization of two separate masks. Bottom copper electrodes for capacitors were also defined during the resistor fabrication process. Photodefinable epoxies filled with a high permittivity ceramic powder were used for fabrication of thin film capacitors. Epoxy and ceramic powders were mixed in the required proportion and blended using a high shear apparatus. The coating solution was homogenized in a roll miller for 3 to 5 days prior to casting in order to prevent settling of the higher density ceramic particles. Capacitors were fabricated by spin-coating on the sub-etched copper electrodes. The deposited dielectric layers were dried, exposed with UV radiation, patterned, and thermally cured. Top capacitor electrodes (copper) were deposited using a metal or an e-beam evaporator. The electrodes were patterned using the standard photolithography processes. Selected good samples were used for depositing the second capacitor layer. The RC network is extended to incorporate electroplated polymer/ferrite core micro-inductors through the fabrication of an industry prototype low pass RLC filter. Meniscus coating was evaluated for large area manufacturing with high process yield. A capacitance density of ∼3 nF cm−2 was obtained on a single layer capacitor with ∼6 μm thick films. The capacitance density was increased to ∼6 nF cm−2 with the two-layer deposition process. The capacitors were relatively stable up to a frequency range of 120 Hz to 100 KHz. Meniscus coating was qualified to be a viable manufacturable method for depositing polymer/ceramic capacitors on large area (300mm x 300mm) PWB substrates. Dielectric constant values in the range of 3.5 to 35 with increase in filler loading up to 45 vol% were achieved in the epoxy nanocomposite system where the dielectric constant of the host polymer was limited to ∼3.5. Higher dielectric constant polymers are required to meet the increasingly higher capacitance needs for the next generation electronics packaging. Possible avenues for achieving higher capacitance density in polymer/ceramic nanocomposite system have been discussed.

Next generation integral passives: materials, processes, and integration of resistors and capacitors on PWB substrates

Calcium orthophosphate deposits: Preparation, properties and biomedical applications.

Microarc oxidation (MAO) was performed on Ti–6Al–4V in electrolytes containing calcium glycerphosphate (Ca-GP) and calcium acetate (CA) using a regulated direct current power supply. It was found that the MAO method was suitable for Ti–6Al–4V to form a ceramic coating in electrolytes of Ca-GP and CA, and the oxide films displayed a porous and rough structure on the surface of films. The film with a Ca/P ratio equivalent to hydroxyapatite was obtained when final voltage and current density were 350 V and 200 A/m2 in the electrolyte containing 0.06 M calcium glycerphosphate (Ca-GP) and 0.25 M calcium acetate (CA). After hydrothermal treatment, the hydroxyapatite was precipitated on the surface of the film obtained by MAO and the hydroxyapatite thickness was about 4 μm. The films were investigated by means of electron probe micro-analysis, atomic force microscopy, X-ray diffractometry and scanning electron microcopy before and after hydrothermal treatment.

Formation of hydroxyapatite on Ti–6Al–4V alloy by microarc oxidation and hydrothermal treatment

Formation characterization of hydroxyapatite on titanium by microarc oxidation and hydrothermal treatment.

The biomedical NiTi alloy was treated by micro-arc oxidation in an electrolytes containing sodium aluminate and sodium hypophosphite at 400 V constant voltages for 30 min. The MAO-treated NiTi has a porous microstructure on its surface and coatings consisting only of the γ-Al 2 O 3 phase. The ceramic coating prepared by micro-arc oxidation is composed of Al, Ti, Ni, O, and P with the atomic concentration of 26.98%, 3.67%, 3.33%, 65.30% and 0.72%, respectively. The MAO-treated NiTi was soaked in a simulated body fluid (1.0SBF) to investigate the biomimetic deposition of apatite on the surface of Al 2 O 3 coated NiTi alloy. It was found that Al 2 O 3 coated NiTi alloy shows an excellent apatite-forming ability after soaking in a simulated body fluid (1.0SBF) for 14 days, while no apatite-forming ability was observed on bared NiTi alloy even though soaking time is up to 28 days.

Biomimetic deposition of apatite coatings on micro-arc oxidation treated biomedical NiTi alloy

Hydroxyapatite formation on oxide films containing Ca and P by hydrothermal treatment

A fibrous lead titanate (PbTiO3) powder with light-yellow colour has been prepared by hydrothermal synthesis. The influences of Pb/Ti ratio (0.3 to 1.0) in the mixture and reaction time on the formation of fibrous PbTiO3 under hydrothermal conditions have been investigated. The preferable conditions for preparing fibrous perovskite-type PbTiO3 from fibrous potassium titanate are that the Pb/Ti ratio is 1.0, reaction temperature 150 °C and time 72 h. The particles of fibrous powder of perovskite type are usually less than 2 μm in diameter and more than 50 μm in length. The fibrous morphology is essentially unchanged up to about 650 °C, but it disappeared after heating to 1000 °C.

Tadao Shimizu

Papers

Formation of hydroxyapatite on Ti–6Al–4V alloy by microarc oxidation and hydrothermal treatment

Formation characterization of hydroxyapatite on titanium by microarc oxidation and hydrothermal treatment.

Biomimetic deposition of apatite coatings on micro-arc oxidation treated biomedical NiTi alloy

Hydroxyapatite formation on oxide films containing Ca and P by hydrothermal treatment

Hydrothermal synthesis of fibrous lead titanate powders