Zirconium Tin Titanate Research Articles

Erosive smoothing of abrasive slurry-jet micro-machined channels in glass, PMMA, and sintered ceramics: Experiments and roughness model

Abrasive slurry jet micro-machining (ASJM) was used to machine channels in glass, PMMA, zirconium tin titanate, and aluminum nitride. The channel roughness was measured as a function of the ASJM process parameters particle size, dose, impact velocity, and impact angle. The steady-state roughness of the channels was reached relatively quickly for typical ASJM abrasive flow rates. The roughness of channels having depth-to-width aspect ratios up to about 0.25 could be reduced by approximately 35% compared to the roughest channel by decreasing particle impact velocity and angle. However, machining at such conditions reduced the specific erosion rate by 64% on average. It was therefore quicker to post-blast reference channels (225nm average root mean square (Rrms) roughness) using process parameters selected for peak removal. It was also found that the roughness of reference channels could be reduced by about 78% by post-blasting using 3μm diameter silicon carbide particles at 15° jet incidence. The smoothest post-blasted channels had an Rrms roughness of about 23nm in glass, PMMA, and zirconium tin titanate, and 170nm in aluminum nitride. Computational fluid dynamics was used to predict the particle impact conditions that were used in a model to predict the steady-state roughness due to ductile erosion with an average error of 12%.

The effects of fluid vapor pressure and viscosity on the shapes of abrasive slurry-jet micro-machined holes and channels

Abrasive slurry jet micro-machining (ASJM) can etch micro-features such as holes and channels in virtually any material. Holes, and to a lesser extent, channels machined in brittle materials using ASJM typically suffer from substantial edge rounding near the opening. This study investigated the erosive mechanism responsible for the rounding in borosilicate glass and sintered zirconium tin titanate targets, and determined the process parameters capable of minimizing the effect. Computational fluid dynamics (CFD) showed that the rounding that occurred during ASJM with a water-based slurry was due to the impact of particles accelerated by the formation and collapse of cavitation bubbles in regions where local pressures were below the vapor pressure of water. Further evidence of this was obtained by comparing the micro-topography in these regions with that produced by an ultrasonic cavitation apparatus in a water-particle slurry. Cavitation-enhanced erosion in ASJM was minimized using liquids such as mineral or soybean oil that have relatively low vapor pressures, resulting in blind and through-holes having sharp entrance and exit holes in glass and sintered zirconium tin titanate. The increased viscosity of the test fluids also altered the particle trajectories observed in the CFD models, causing the cross-sectional shape of the holes to have flatter bottoms and steeper sidewalls. In ductile targets such as copper, edge rounding due to cavitation-enhanced erosion was found to be much smaller than in brittle targets. In glass channels, the use of a soybean oil-based slurry eliminated the edge rounding and resulted in flatter bottoms, but increased the width by approximately 20%.

Spark Plasma Sintering of Dielectric Ceramics Zr0.8Sn0.2TiO4

Zirconium-tin titanate ceramics (Zr,Sn)TiO4 was prepared by spark plasma sintering (SPS) technique. Resulting samples, low-height cylinders, were subjected to microstructural observations, immersion measurements of density and porosity and X-ray diffraction phase analysis. Dielectric parameters – relative permittivity and loss factor – were tested in the frequency range from 80 Hz to 1 MHz and volume DC resistivity at 100 volts.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.8767

High-Resolution, Far-Field, and Passive Temperature Sensing up to 700 °C Using an Isolated ZST Microwave Dielectric Resonator

This paper presents a high-resolution, wireless and passive temperature measurement system up to 700 °C. The sensor is based on a metallization-free monolithic microwave dielectric resonator composed of zirconium tin titanate (Zr0.8Sn0.2TiO4) operating at 2.37 GHz. The external electromagnetic fields of the tracked single mode are adequate for the far-field coupling without the need to use any conducting part on the sensor surface. The measurements are conducted in a light weight refractory bricks oven at a distance of 1.20 m between the sensor and a reader planar antenna connected to a time-domain RADAR-based interrogation unit. This method allows to retain a quality factor ( $Q$ ) higher than 670 at 700 °C, while the $Q$ -factor from other electromagnetic cavity or microwave dielectric resonators degrades below 100, hence limiting the sensing resolution and increasing the sensitivity to the environmental echoes. The effect of temperature on the tracked sensor resonance frequency, signal-to-noise ratio, $Q$ -factor, thermal expansion, and sensing resolution is presented. The concept is suitable for applications working in extreme environments, such as aerospace applications.

CFD-aided prediction of the shape of abrasive slurry jet micro-machined channels in sintered ceramics

The extreme hardness of sintered ceramics makes it difficult to machine them economically. Abrasive slurry-jet micro-machining (ASJM), in which a target is eroded by the impingement of a micro-jet of water containing fine abrasive particles, is a low-cost alternative for micro-machining of sintered ceramic materials without tool wear and thermal damage, and without the use of patterned masks. Existing profile prediction models could not account for changes in the flow field observed in the ASJM of sintered ceramics as channel depth increased. These changes in the flow of abrasive particles fundamentally altered the channel profiles so that the specific erosion rate (mass of material removed per mass of erodent) of the channel centerline decreased with increasing depth and, when machined at 90° incidence, the profiles changed shape. Computational fluid dynamic (CFD) modeling was used to derive a generalized relation between channel geometry and erosive flow (the nonlinearity function), which was used in an existing numerical-empirical model to predict the depths, widths, and shapes of ASJM micro-channels in sintered ceramics; i.e. aluminum nitride (AlN), alumina (Al2O3), and zirconium tin titanate (Zn–Sn–TiO2). The specific erosion rate-particle impact angle and specific erosion rate-particle impact velocity relations, measured for 1wt%, 10μm-diameter alumina slurry jet, were used in a CFD model of a first-pass channel to obtain the erosive pattern (erosive efficacy distribution) of the slurry jet within a shallow ceramic channel. This shallow, first-pass erosion pattern was then generalized and used with the nonlinearity function to predict the shapes of deeper channels. The predicted depths in each of the three ceramics at any point on the cross-section were within 6% of those of measured channels up to a depth/width aspect ratio of about 0.5 for nozzle angles of both 90° and 45° in both the forward or backward channel-machining configurations.

Hybrid erosive jet micro-milling of sintered ceramic wafers with and without copper-filled through-holes

Abrasive slurry jet micro-machining (ASJM) in combination with abrasive air jet micro-machining (AJM) was used to mill micro-pockets in three different ceramic wafers: sintered alumina, aluminum nitride, and zirconium tin titanate. A composite substrate of aluminum nitride with an array of copper-filled through-holes was also machined using a hybrid process of AJM and ASJM that capitalized on the significant differences in the erosive characteristics of each method. The objective was to investigate an alternative to laser micro-milling. The sintered ceramics were found to erode in a brittle manner by the dislodgment of grains upon abrasive particle impact. The eroded profiles produced by ASJM and AJM were modeled analytically.ASJM could make 100μm deep flat pockets, 500μm wide with 60° sidewall angles in the sintered ceramics using overlapping parallel channels. The shapes of the pockets could be predicted accurately as long as the depth of each machined pass was less than 50μm. Pockets of the same size and roughness (Ra=0.4μm) could also be machined and modeled accurately using masked AJM. The surface roughness of the sintered ceramics was found to be insensitive to particle size, being controlled by the size of the sintered grains.Similar pockets could be machined in the aluminum nitride containing 180μm diameter copper through-holes using ASJM provided that the maximum depth was about 25μm. Beyond that, the secondary slurry flow away from the jet footprint created unwanted etching of the copper-filled through-holes leading to a lack of flatness. Deeper pockets in these substrates were machined using a hybrid AJM–ASJM methodology, in which AJM was used to selectively erode the brittle sintered ceramic without etching the ductile copper, followed by the leveling of the protruding copper pillars to the depth of the ceramic using ASJM. Computational fluid dynamics models were used to explain the results in terms of the large differences in the local particle impact angles and velocities in ASJM and AJM.

Effect of electric field on dielectric properties of antiferroelectric ceramic/polymer composites

Antiferroelectric ceramic/polymer composites can be used as a base material in the future application of the tunable photonic crystals even high strain actuators, shock-activated energy transducer and high-density capacitor for their easy fabrication, good flexibility, precise control of the process parameters and good dielectric tenability affected by electric field. The adjustable dielectric effect in the antiferroelectric ceramic/polymer composites are experimentally studied with specific interest in the dependence on the inducing electric field up to 100 V/mm. The particulate composite consisting 20 vol% of polystyrene (PS), 80 vol% of lead barium lanthanum zirconium tin titanate (PBLZST) is fabricated by the means of solution mixing and hot pressing in lab. Scanning electron microscopy was used to investigate the morphology of the composites and the particle distribution, which shows that the nano carbon powders evenly dispersed in composite materials. It is observed that the addition of coupling agent and nano carbon powders influence the dielectric properties, such as the value of the tunability rate of dielectric permittivity and loss tangent. This is partly attributed to coupling agent improve two phase separation and enhanced the effect of ceramic phase in composites, and partly attributed to carbon powders which create electric paths between PBLZST Particles in composite material, which together make more electric field applied to ceramic phase and influence the response of dielectric permittivity controlled by electric field. As a result, the best electric field value to adjust the dielectric permittivity (e) is 100 V/mm and maximum tunability rate was 49 %, with coupling agent at 10 wt% and nano carbon powders at 1 wt% in composites.

High dielectric constant EBG technology to avoid gratings lobes and scan blindness in array configurations

High dielectric electromagnetic band gap (EBG) substrates can be used in patch antenna configurations to reduce size and mitigate substrate modes propagation with reasonable radiation efficiency values (ηrad > 0.55). Furthermore, EBG substrate structures applied in array configurations are able to avoid grating lobes and scan blindness phenomena as distance and coupling between patch antenna-radiating elements can be reduced at the same time. In this paper, a 2 × 2 array configuration using Zirconium Tin Titanate EBG substrate with high dielectric constant is presented. The array has been simulated showing 9 dB coupling reduction obtained by the inclusion of the EBG substrate in between the patch antennas placed to a distance lower than 0,5λ0. This short distance together with the coupling reduction results in a configuration which does not suffer from grating lobes and scan blindness problems, obtaining a 30º scan angle for the 2 × 2 configuration which is the maximum achievable angle due to a 2 × 2 array factor. A scan angle larger than 70º can be seen for the infinite configuration.

DR OMUX for Satellite Communications: A Complete Step-by-Step Design Procedure for the C-Band Dielectric Resonator Output Multiplexer

Although the behavior of dielectric materials has been known since 1939 when R.D. Richtmyer showed that unmetalized dielectrics can operate as microwave resonators [1], it was only in the 1970s when real breakthroughs occurred in ceramic technology, and low loss and temperature stable ceramics were developed. In 1975 the first practical dielectric resonator (DR) loaded microwave filter was reported at the IEEE MTT-S International Microwave Symposium [2]. Significant advancements in ceramic technology and the progress in satellite and mobile communications in the 1990s revived interest in DR applications for a wide variety of microwave components. A number of new materials such as zirconium-tin titanate, ZST ((Zr ? Sn)TiO4), barium zinc tantalate, BZT (Ba(Zn,Ta)O3), and barium magnesium tantalate, BMT (Ba(Mg,Ta)O3), with high-dielectric constant, high-quality factor and low-temperature coefficient were developed [3]. These new materials, along with the application of rigorous full-wave modeling and analysis methods, fueled the development of new DR filter configurations such as single and dual mode filters with elliptic transfer function. Today, DR filters and output multiplexers (OMUXs) are widely used in satellite communications because of their superior characteristics, such as smaller size, better temperature stability, and higher unloaded Q compared to conventional cavity-based OMUXs. A number of papers have been published on DR filters and OMUXs [4]?[6], [8], [9], but no comprehensive paper on the design of a DR-based OMUX has been reported. The large interchannel interaction (due to contiguity of channel filter frequencies, performance of one channel filter is effected by the presence of other channel filters), wide spurious free frequency band, and stringent in-band and out-of-band (OOB) specifications (such as large near band and far band rejections, small passband group delay and flatness), along with the requirement of high Q, low frequency drift with temperature, and high power handling capability, make the design of DR OMUXs extremely challenging. This article presents a practical approach to the design of C-band high power OMUXs based on single mode DR filters for space application (Figures 1 and 2), making extensive use of present day simulation capabilities. All the major steps involved in the design of a DR OMUX such as the concept of a singly terminated filter, conversion of doubly terminated filters to singly terminated filters using a series L-C circuit, modeling of the DR OMUX in a circuit simulator incorporating full wave effects, and the OMUX optimization sequence are explained in detail. A successful design of the DR filter is crucial to the eventual design of the DR OMUX.

Sintering and Microwave Properties of Zirconium Tin Titanate Doped with Select Oxides

Zirconium tin titanate (ZST) is often used as a dielectric resonator for the fabrication of microwave devices. Pure compositions do not sinter easily by solid state sintering; therefore, sintering ZST requires sintering aids capable of creating defects that could improve diffusion processes and/or promote liquid phase sintering. The mechanisms by which the additives influence the microstructure and, consequently, the ZSTs dielectric properties are not very clear. The effects of ZnO, Bi2O3, and La2O3, on the stoichiometry and dielectric properties of ZST sintered at different temperatures were investigated in this study.

Preparation and Characterization of ZST Films for CMOS Applications

Zirconium tin titanate (Zr, Sn)TiO4 (ZST) thin films have been deposited at ambient temperature by dc magnetron sputtering from individual titanium, zirconium and tin metal targets on platinized silicon substrates. The present study demonstrates the possibility of growing zirconium tin titanium oxide films in 100% pure dc oxygen plasma. Films having thickness of the order of 450 nm have been grown starting from the metallic Zr, Ti and Sn targets in pure oxygen plasma. The grains as observed from atomic force microscope images are found to be a mixture of spherical and triangular geometry. The maximum value of dielectric constant and loss are found to be 53.7 and 0.0075 (at 5 MHz) for the films deposited at 40% Oxygen Mixing Percentage (OMP). The magnitude of current density and the breakdown field strength of the ZST films deposited at 40% OMP are found to be 9.72 × 10−7 Amp/cm2 and 62.5 KV/cm respectively. The effect of processing parameters on structural, microstructural, optical, dielectric and electrical properties of the (Zr,Sn)TiO4 films have been investigated.

Effect of annealing on microstructure of CuO-doped (Zr 0.8Sn 0.2)TiO 4

Zirconium tin titanate ceramics, and specifically the (Zr 0.8Sn 0.2)TiO 4 (ZST) are the preferred materials for use in resonators or filters working at microwave frequency. However, the problem with these materials is their high sintering temperature which is as high as 1550 °C. In this research, the influence of different amounts of CuO additions on the densification and microstructure evaluations of ZST ceramics modified with 1 wt% ZnO has been studied in two different states: before and after annealing. Results showed that annealing process at 1250 °C resulted in some changes in density, grain size and shape due to the rearrangement of liquid phase and its reactivation, but no secondary phase was detected. Also, variations in lattice parameters during annealing compared to those of as-sintered specimens suggested the possibility of disorder–order transformation during long time high temperature heat treatment process.

Miniaturized high impedance surfaces with angular stability by using zirconium tin titanate substrates and convoluted FSS elements

AbstractA new approach for obtaining metasurfaces realized by using frequency selective surfaces with reduced periodicity printed on a new class of high dielectric constant materials is presented. The proposed engineered ad‐hoc materials and the innovative electromagnetic design provide an improvement of the overall device in terms of compactness and angular stability, as shown by the use of our novel band vs. incidence angles chart. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2753–2758, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24731

Optical and microwave characteristics of ambient temperature deposited zirconium tin titanate high-kfilms

High- k (Zr,Sn)TiO 4 films were grown on glass substrate by DC magnetron sputtering at ambient temperature using elemental, all metallic targets. Films were polycrystalline irrespective of the oxygen partial pressure. The refractive index and optical bandgap of the films were in the range 1.79–1.59 at 600 nm and 3.27–3.39 eV, respectively. Highest value of microwave dielectric constant exhibited was 33 and lowest loss tangent was 0.001 at 10 GHz. Films prepared at 40% oxygen mixing percentage (OMP) gave minimum strain and the same film gave minimum dielectric loss with highest dielectric constant. A correlation between strain values and dielectric loss was observed. The grain sizes as observed from atomic force microscope images are found to be triangular in nature.

Pulsed electron beam deposition of oxide thin films

In this work we studied the pulsed electron beam deposition (PED) method using a channel-spark discharge as the electron source. In order to estimate the potential of the PED method, thin films of zinc oxide, zirconium tin titanate, barium strontium titanate and biocompatible oxides were grown and investigated taking into account two important points: the surface morphology and the film composition. We showed that PED leads to films free from micrometre size droplets and by a careful optimization of the beam parameters it is possible to drastically reduce the density and size of nanoparticulates. In fact, by studying the relationships between the discharge parameters, electron beam characteristics and surface morphology of films we evidenced that a decrease in the beam energy leads to a drastic reduction in the nanoparticulate density. The composition of the various oxide thin films investigated in this work is close to that of the target, as in the case of pulsed laser deposition, even in the case of complex oxide compounds. Hence, smooth and dense thin films preserving the composition of the bulk target can be obtained by the PED method. The study by fast imaging of the expansion of the plasma plume produced by the pulsed electron beam interaction with the target indicates that the kinetic energy of the species emitted by the target is roughly in the 10–50 eV range.

Effect of annealing temperatures on microstructure of (Zr 0.8Sn 0.2)TiO 4 thin films grown by a sol–gel process

The impact of annealing temperatures on microstructures of zirconium tin titanate (Zr 0.8Sn 0.2TiO 4, ZST) thin films grown by a sol–gel process is proposed. ZST thin films were deposited along the (1 0 0) orientation p-type Si substrate and were characterized by XRD, AFM, SIMS and TEM. Amorphous and polycrystal films were grown successfully on Si substrates with different annealing temperatures. The chemical compositions of the films were detected and showed a uniform concentration distribution for all species. Due to the interface layer formed during the annealing process, the dielectric constants of 81-nm-thick ZST films in the present study were ∼16.

Microstructure and electrical properties of (Zr, Sn)TiO4 thin film deposited on Si(1 0 0) using a sol–gel process

Polycrystalline zirconium tin titanate (Zr0.8Sn0.2TiO4, ZST) thin films with thickness of 81nm were deposited successfully along the (100) on a p-type Si substrate by an improved sol–gel method. The deposited films were crystallized when annealing temperature was up to 450°C. The thickness and compositions of the interface layer between the ZST films and Si substrate were identified by high-resolution transmission electron microscope (HRTEM). The electrical properties such as leakage current density, flat-band voltage and capacitance of the films were measured and discussed. Furthermore, the mechanism of the leakage current was also investigated.

Effect of Thickness on the Structural and Electrical Properties of Sol-Gel-Derived (Zr,Sn)TiO[sub 4] Thin Films

Zirconium tin titanate (Zr 0.8 Sn 0.2 TiO 4 , ZST) thin films were deposited along the (100) index on a p-type Si substrate by a modified sol-gel method. The effects of film thickness on the crystalline structure and electrical property of the ZST films were investigated. X-ray diffraction confirmed a pronounced preferred orientation in thinner films and a polycrystalline structure in thicker films. The relationship between the leakage current densities and different crystalline structures is discussed. The leakage current densities of the prepared ZST films were below 10 -7 A/cm 2 at 3 MV/cm, which were sufficiently small to be a candidate for application in dynamic random-access memory (DRAM).

Nano powder and Microwave Dielectric Properties of Sol–Gel-Derived Zr0.8Sn0.2TiO4 Ceramics

The Nano powder and microwave dielectric properties of zirconium tin titanate (Zr0.8Sn0.2TiO4, ZST) ceramics prepared by sol–gel process were investigated. Pure and fine ZST powders with particle sizes of 10–20 nm were derived by thermal decomposition of an amorphous gel precursor at about 700°C. They formed a single orthorhombic ZST phase and appeared fine and well-dispersed in both scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM). The high sintering ability of the prepared powders enabled the fabrication of dielectric ceramics at low sintering temperatures (1250–1300°C). The well-sintered ZST ceramics with high relative densities (96%) showed excellent microwave dielectric properties compared with those prepared by a conventional method at the same sintering temperature.

High Quality Microwave Zr0.8Sn0.2TiO4 Dielectric Thin Film Prepared by Sol–Gel Method

High-quality zirconium tin titanate (Zr0.8Sn0.2TiO4, ZST) thin films are deposited along the (100) plane on a p-type Si substrate by the sol–gel method. The effects of two different heat treatment temperatures, 250 and 450°C, for organic burn-out between each spin coating on the crystal structure, morphology, roughness and thickness of the films are investigated. X-ray diffraction confirms a pronounced preferred orientation in thinner films and a polycrystalline structure in thicker films. Microstructure analyses by scanning electronic microscopy (SEM) and atomic force microscopy (AFM) prove that a high-quality ZST film approximately 75 nm thick with a smooth surface (surface roughness of 4 nm) is obtained under suitable processing conditions.