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The effects of calcination time and sintering temperature on the properties of Ca[Cu.sub.3][Ti.sub.4][O.sub.12] are examined. Results suggest the complete formation of a single-phase of Ca[Cu.sub.3][Ti.sub.4][O.sub.12] by calcination at 750 degree Celsius for 12 hours.

Research in phase equilibria and crystallography has been a tradition in the Ceramics Division at National Bureau of Standards/National Institute of Standatrds and Technology (NBS/NIST) since the early thirties. In […]

Research describing the effect of dc electric fields on the behavior of cadmium pyroniobate is presented. In particular the field dependence of the dielectric constant and loss are investigated.

Research describing the complex dielectric permittivity of lossy ceramic composites is presented. In particular an AlN composite is investigated with regard to the phasing out of BeO composites on environmental and safety grounds.

Research describing parametric phase conjugation of ultrasound waves is presented. Increased average output power by means of multifrequency operation of the phase conjugator is demonstrated.

The authors propose a low-cost, relatively simple resonance testing to measure the new parameters for electroactive materials. A pair of coupling parameters can, with this method, characterize the material's electromechanical quality.

A study investigated the use of mechanical indentation with conducting spherical indentors, with zero potential basis, as a technique for characterizing piezoelectric ceramic-polymer 1-3 composites. The measured currents as a function of load, at larger loads, are in qualitative agreement with those predicted using analytical and finite element models based on given electromechanical properties of the constituents.

The effective dielectric, piezoelectric and elastic constants of polycrystalline ferroelectric materials were determined from single-crystal data through an advanced technique of effective medium. The technique considers the piezoelectric interactions between grains in full measure. The material constants were found to be dependent on the remanent polarization for bulk BaTiO3 and PbTiO3 polarized ceramics. Dielectric and elastic constants were also obtained for unpolarized c- and a-textured ferroelectric thin films deposited on cubic and amorphous substrates.

Research was conducted to examine the dielectric properties of Bi doped SrTiO3 ceramics in the temperature range 500-800 K. Ceramic samples were prepared using solid state reaction. Temperature dependence of dielectric properties was calculated while the temperature of samples was increasing at a rate of 0.7 K/min an readings were taken at every 3 K. Results indicate that the permittivity peaks are related to the movement of oxygen ions.

Research was conducted to investigate the fragmentation and flow of hot-pressed silicon carbide under high-strain-rate deformation and comminution of silicon carbide. Three different silicon carbides having similar average grain size were examined based on their fragmentation and large deformation of ceramics. Results indicate that high-strain-rate deformation of comminuted SiC is applicable in the validation of computer models for penetration process.

The influence of mobile space charges on the ferroelectric properties is investigated by measuring the ac complex impedance and thermal depolarization current for aged (K0.50Na0.50)2(Sr0.75Ba0.25)4Nb10O30 ceramic samples. An analysis of the impedance behavior was done through an equivalent circuit composed of a capacitor connected in series with a parallel resistor-capacitor circuit. Experimental results show that the dielectric relaxation consists of two mechanisms which are discussed.

Microhardness profiles were used to monitor the density at BSCCO/Ag wires' and tapes' transverse cross sections after several deformation processes. Results provide an explanation of the deformation process and indicate the type of deformation is ideal for developing homogeneous and dense BSCCO-core through the powder-in-tube method. Results also stress the importance of optimal core density values in achieving high transport currents.

Photoemission spectroscopy was used in studying the surface properties of CuBa2Ca3Cu4O12-delta superconducting ceramics. Ultra-high vacuum annealing at temperatures below 150-degrees celsius was conducted to enhance the materials' surface electronic structure for applications in high performance contacts. A contact resistivity as low as 1x10(super -8) ohmcm2 was achieved using the approach.

A study was conducted on the fracture resistance and microstructural properties of superconductive ceramics. A computer model for crack bridging processes was employed in analyzing three types of restraining bridges, namely, frictional ligaments, elastic connections and tractions caused by thermal expansion anisotropy. An evaluation was then performed on the effects of initial press-powder porosity on certain crack bridging parameters.

Bulk samples of (Bi,Pb)2Sr2Ca2Cu3O10 were sintered for different times and then isothermally pressed at 850-degrees celsius under a constant pressure of 15 MPa for 1 hour. Critical temperature, mass density and critical current density were measured using EDS, XRD and scanning electron microscopy. The removal of voids in the materials under pressure and high temperature resulted in a significant increase in mass density.

The interactions between thick-film resistors and the dielectric layers of a low-temperature, cobalt-fired, integrated ceramic package were examined. The reactions, which occurred during co-sintering, were influenced by the microstructural and microchemical characteristics of the glass phase of the resistor material. These explained why the glass flow at the sintering temperature and the activity gradients between components at the glass phase were able to control the kinetics and thermodynamics of the reactions.

(Pb,La)(Zr,Ti)O3 and Pb(Zr,Ti)O3 bulk ceramics and thin films reveal two photoinduced modifications in their hysteresis properties, a voltage shift and a reduction of switchable polarization. Photogenerated charge capture at domain boundaries results in a decrease in internal depolarizing fields and accounts for the photoinduced-changes in hysteresis. Polarization-inhibition depends on exponential time while voltage shift depends on stretched exponential time and thickness of the film. The relaxation times of both effects is same, but that of the voltage shift effect decreases when light intensity increases.

X-ray measurements of the dielectric constant, dielectric polarization, crystallographic parameters and electrostrictive strain of lead zirconate titanate stannate ceramics with lanthanum reveal that the electric field activates the transition from the antiferroelectric to ferroelectric phase. The transition occurs with a volume modification of 0.35 cubic Angstrom units and is the most dominant process in the strain. The parameters of ceramics depend on the technology of ceramic formation while the backward switching critical field depends on temperature.

Interconnection and placement requirements are the impediments in the miniaturization of electronic system beyond the 0402 size. A new approach for miniaturization uses ceramic multilayer technology and thick film resistor networks. Design of ceramic multicomponent modules involves the integration of capacitors and resistors into a single ceramic module. This technique enables the design of high density of functions in an easy mountable package.

An equivalent circuit with a frequency-dependent capacitor substitution explains the ac electrical reactions for (Ba,Pb) TiO3 ceramics, and the importance of constant n displayed in the depressed circular arcs. This design illustrates that a resistance state above Tc will give a more efficient semicircular, and that the positive temperature coefficient of resistance is affected by the conduction characteristics of the grain boundary.

Microwave sintering of ceramics in multimode cavities, particularly the use of picket-fence arrangements, has recently received considerable attention. Various types of ceramics have been successfully sintered and, in some cases, a desirable and unique 'microwave effect' has been observed. At present, various aspects of the sintering process such as preparation of sample sizes and shapes, types of insulations, and the desirability of including a process stimulus such as SiC rods are considered forms of art and highly dependent on human expertise. The simulation of realistic sintering experiments in a multimode cavity may provide an improved understanding of critical parameters involved and allow for the development of guidelines towards the optimization of the sintering process. In this paper, we utilize the FDTD technique to model various geometrical arrangements and material compatibility aspects in multimode microwave cavities and to simulate realistic sintering experiments. The FDTD procedure starts with the simulation of a field distribution in multimode microwave cavities that resembles a set of measured data using liquid crystal sheets. Also included in the simulation is the waveguide feed as well as a ceramic loading plate placed at the base of the cavity. The FDTD simulation thus provides realistic representation of a typical sintering experiment. Aspects that have been successfully simulated include the effects of various types of insulation, the role of SiC rods on the uniformity of the resulting microwave fields, and the possible shielding effects that may result from excessive use of SiC. These results as well as others showing the electromagnetic fields and power-deposition patterns in multiple ceramic samples are presented.

Glass+ceramics with low dielectric values aid the densification of multilayer ceramic substrates having alumina, borosilicate glass and high silica glass at less than 1,000 degrees Celsius in air. This increases electrical conductivity metallization. Analytical studies and a mixing rule help fabricate this cristobalite-free ternary system with desired properties.

The electrical properties of lead-lanthanum zirconate-titanate-x/95/5 ceramics with an La content ranging from 4 to 5% were investigated. The results showed that La dopants exerted a strong effect on the antiferroelectric-ferroelectric-paraelectric phase transitions and properties of the material. Ferroelectric microdomains induced the formation of properties like those observed in ferroelectric relaxors.

The results of a numerical study conducted by R Feng et al and Feng and YM Gupta were analyzed. The study was carried out to gain an insight into the dynamic response of lateral piezoresisting stress gauges. The results were investigated to highlight the difficulties with the simulations and to focus on several conclusions concerning the choice of optimal gauge dimensions and emplacement methods.

The comment made by Z. Rosenberg regarding two studies conducted on lateral piezoresistance gauges in shocked ceramics and shocked solids were found to be invalid. There were also misleading statements pertaining to the previous studies that Rosenberg reviewed. A response to the comment is presented which focuses on such points as the agreement between his assumptions and the reviewed dynamic calculations and his ad hoc statements about the numerical calculations.

The magnetic properties of nanocrystalline FeHfC single layered and FeHfC/ceramics (AlN, [Al.sub.2][O.sub.3], [Si.sub.3][N.sub.4], Si[O.sub.2]) multilayered films were investigated. The soft magnetic properties of the multilayered films laminated by the Al-based ceramics were better, but those of films laminated by the Si-based ceramics were worse than the magnetic properties of single layered films. An analysis of multilayered structure revealed that FeHfC/AlN and FeHfC/[Al.sub.2][O.sub.3] films maintained better periodic structure than FeHfC/[Si.sub.3][N.sub.4] and FeHfC/Si[O.sub.2] films. The present results suggest that the interdiffusion effect plays an important role in determining the magnetic properties of the multilayered films.

An introduction and advanced picture of dielectric relaxation in solids and dielectric data interpretation is presented. The description of the principles of dielectric spectroscopy (DS) that are useful for practical situations, irrespective of the field is discussed.

Ferroelectric properties of 9% mol (Hf,Zr)-doped BaTi[O.sub.3] ceramics have been studied by comparison with those of pure tetragonal BaTi[O.sub.3] ceramics. The addition of doping ions lead to a shift of the rhombohedral to orthorhombic and orthorhombic to tetragonal transition temperatures above 0 [degrees] C, and to a decrease of tetragonal to cubic (ferroelectric to paraelectric) transition temperature from 122 [degrees] C to 95 [degrees] C on heating and from 120 [degrees] C to 85 [degrees] C on cooling. In pure tetragonal ceramics at room temperature, aging develops by a thermally activated process, leading to a linear dependence of the relative permittivity and dielectric loss on the logarithm of time. In case of doped ceramics, the experiments showed a decreasing reversed-S dependence of capacitance and tan [Delta] on the logarithm of time, suggesting that dielectric aging in these materials is related with defect diffusion. It was concluded that in doped BaTi[O.sub.3] ceramics the aging mechanisms depend on the crystalline symmetry, which influences the twinning process and the domain-wall dynamics. Aging of (Hf,Zr)-doped BaTi[O.sub.3] ceramics depends on temperature and the phase symmetry, which imposes the twinning rate and the rearrangement speed of ferroelectric domains minimizing the elastic energy of the lattice.

Delaminations of embedded passive components are often associated with reliability problems. Understanding the delamination can help us quickly identify the failure caused at an early stage of failure analysis. In this work, defects in buried capacitors have been detected by use of scanning acoustic microscopy (SAM). Defects in buried capacitors caused by thermal shock have also been clearly observed. The results show that SAM can be a powerful analytical tool for the nondestructive evaluation of delaminations in buried passive components. Through transmission scan (THRU-scan) is a fast method to detect the existence of internal defects, while Tomographic Acoustic Multiple Imaging scan (TAMI-scan) is shown to be capable of detecting the location and size of delaminations and voids. [S1043-7398(00)01102-6]

This paper outlines a method of tuning a microwave broadside coupler buried in the low-temperature co-fired ceramic. Etching a slot in the exposed ground plane tunes the characteristic impedance [Z.sub.0] of a stripline coupler. An iterative method computes the correct dimensions of the slot. Applying the method salvages microwave circuits detuned due to manufacturing tolerances. Index Terms--Co-fired, low temperture, Multilayer ceramic, stripline coupler.

The first volume of a collection of phase diagrams focused on the increasingly important field of electronic ceramics was presented to the American Ceramic Society (ACerS) at its annual meeting […]