Conventional Ceramic Processing Research Articles

Low loss Z-type Hexaferrites with Bi2O3 Additives for Ultra-high Frequency Antenna Applications

The Z-type ferrites of nominal composition Ba3Co2Fe24O41+x wt% Bi2O3, where x=0.25, 0.5, 1.0, 1.5, 2.0, were prepared by conventional ceramic processes. The influence of Bi2O3 content on the bulk densities, microstructures, magnetic and dielectric properties of Z-type ferrite samples were systematically examined so as to obtain materials with low magnetic and dielectric loss tangent over a frequency ranging from 600 to 800 MHz. The experimental results showed that addition of Bi2O3 lowered the sintering temperature (1 020 ℃) and then reduced the average grain size ( 2.68×108 Ω•cm) dramatically, which consequently decreased the magnetic and dielectric loss. Additionally, the low loss factors were observed at the Bi2O3 content x = 1.0, i e, tan δμ/μ’ = 0.013 and tan δe/e’ = 0.001 at 800 MHz, and such materials could be used for antennas miniaturization from 600 to 800 MHz.

Modulation of Magnetic Properties in Ni0.4Zn0.6Fe₂O₄ Spinel Ferrite by Additives

Sintered NiSUB0.4/SUBZnSUB0.6/SUBFe₂O₄ ferrite with various additives, namely, CoO, Cu₂O, SiO₂, CaCO₃, and MgO was prepared by conventional ceramic processes. The formation of a single-phase cubic spinel structure was confirmed by powder X-ray diffraction. The microstructure and magnetic properties of the samples were significantly changed by the type of additive. In the frequency-dependent complex permeability (μ

Li7La3Zr2O12-PEO Composite Electrolytes and the Role of Interface Resistance

Composite electrolytes consisting of both polymer and ceramic solid state electrolytes have recently received more attention because of their potential to combine high ionic conductivity, facile interface formation and simplified processing compared to conventional ceramic processing routes. Ceramics (e.g. Li7La3Zr2O12 (LLZO)) show high ionic conductivity, but processing the materials into thin membranes is challenging. Energy consuming sintering steps are necessary to obtain dense specimen. In addition, ceramics are brittle, posing further challenges on subsequent processing steps. Polymer electrolytes (e.g. based on poly(ethylene oxide) (PEO)) are facile to prepare by tape casting method and offer flexibility; however, ionic conductivities are lower compared to inorganic materials. Hence, combining both materials forming a composite electrolyte may be a solution. Here, we present the preparation of composite electrolytes consisting of LLZO and PEO based polymer electrolyte with high weight fractions of LLZO. The composites are investigated with regard to their electrochemical properties, paying special attention to the interface between ceramic and polymer. A model system is used to determine the interface resistance between LLZO and PEO as a function polymer electrolyte composition using both experimental and computational methods.

(Invited) Sputtered Thin Films for Very High Power, Efficient, and Low-Cost Commercial SOFCs

Sputtering of thin electrolyte layers has been demonstrated to increase solid oxide fuel cell (SOFC) performance in very small-scale, e.g., button cells. The few cases where thin film techniques were brought in to early stages of commercialization (e.g., Lilliputian and SiEnergy) showed remarkable low temperature SOFC performance, but required sophisticated cell designs processed with Si and MEMs type technologies. This work takes advantage of low cost, conventional ceramic processing to build large format (10 cm x 10 cm) half-cells upon which the sputtered layers above are added to dramatically increase SOFC performance. In this work, an electron-blocking layer which increases the open circuit cell voltage of the GDC electrolyte based cell and a Gd doped ceria (GDC) buffer layer which mitigates reactions between the cathode and electron blocking layer are deposited by sputtering. This presentation will present progress towards developing increased SOFC performance using this sputtering technology at the commercial-scale. Challenges encountered or expected with thin film development for SOFC commercialization will be discussed.

Structural stability, phase transition and dielectric properties of Pb(Mg1/2W1/2)1−xMxO3 (M = Zr,Sn, Ti) ceramics

ABSTRACTPb(Mg1/2W1/2)1−xMxO3 (M = Zr,Sn,Ti) ceramics have been prepared by the conventional ceramic process. Their crystallographic, phase transition and dielectric properties have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer in this paper. The solubility of the tetra-valent cation in Pb(Mg1/2W1/2)1−xMxO3 decreases in the sequence of Ti4+ > Zr4+ > Sn4+. The doping led to the phase transition from orthorhombic antiferroelectric to cubic paraelectric phase, the microscopic nature of which could be attributed to the contraction of Pb-O12 dodecahedron. A definition of the ordering parameter of the cubic phase was deduced to quantitatively evaluate the B-site ordering degree which decreased with the increase in doping concentration. Anti-site disordering of Mg2+ and W6+ occurred in the high-level doping compositions, which led to the relaxor behavior observed in Ti4+-doped series with x = 0.01 composition. Both of the maximum dielectric permittivity and loss in the paraelectric phase increased with the increasing doping concentration.

Net-shaped barium and strontium ferrites by 3D printing with enhanced magnetic performance from milled powders

Net-shaped hexagonal barium and strontium ferrites with desirable shapes have been successfully fabricated by the extrusion-based three-dimensional (3D) printing. The influence of milling and calcination conditions on magnetic properties of as-printed hexaferrites are systematically investigated by vibrating sample magnetometry (VSM). The typical ferromagnetic hysteresis loops are observed, revealing that the resulting bulk ferrites derived from the preliminary milled powders are prefect hard magnetic materials. In particular, it is clear that the saturation magnetization is very close to the theoretical values after calcinations. Moreover, the coercivity can be effectively enhanced in the range of 4–6 kOe upon thermal treatment, which is a much higher value compared to ferrites prepared by the conventional ceramic processing. More importantly, the maximum energy product can be significantly improved to as high as around 2.5 MGOe for the 3D-printed strontium ferrites. This is attributed not only to fine precursor powders subjected to mechanical milling, but also to the optimized annealing for grain growth with sizes near the critical single domain limit. Overall, the fabrication of bulk ferrites derived from milled powders using the 3D printing is attractive for the large-scale applications, and may also pave the way for some specific applications, for instance, magnetic separation for nanoparticles.

Improved electrical performance of MgO-modified CaCu3Ti4O12 ceramics

Colossal permittivity material CaCu3Ti4O12 (CCTO) ceramics modified by MgO with the mass fraction of 0%, 0.5%, 1%, and 2% were synthesized using a sol-gel method followed by a conventional ceramic preparation process. The scanning electron microscope exhibits that all CCTO ceramics possess the high densities and large grain size. The results of dielectric measurement show that all the samples possess giant dielectric properties. The colossal dielectric constant of CCTO ceramics increases firstly and then decreases with the increase of mass fraction from 0% to 2% at room temperature, while the value of dielectric loss is opposite. Specifically, the sample with the mass fraction of 1% shows the highest density, largest grains and most obvious grain boundaries. 1% sample also shows better electrical properties with giant dielectric constant (~6.59 × 104 at 1 kHz) and low dielectric loss (~0.06 at 1 kHz) at room temperature. In addition, the optimal sample with the mass fraction of 1% shows a more stable dielectric constant from 20 °C to 200 °C. The electrical properties of the CCTO ceramics have achieved good performance by the addition of MgO.

Investigation about the reason of limited grain growth of Y-doped barium zirconate

Abstract Yttrium-doped Barium Zirconate is a protonic conductor that shows excellent chemical stability but low sinterability, demanding high sintering temperatures to achieve appropriate densification. However, even after sintering at high temperature, the grain size remains small, resulting in a low electrical conductivity due to the high grain boundary area. This behavior, according to literature, is associated with the high refractoriness. The first contribution of this work is the establishment of a suitable method to prepare the powder, following the fundamentals of conventional ceramic process, that allowed obtaining BZY20 samples with 98% of theoretical density after sintering at 1600⁰C without sintering aid. The second contribution of this paper is to understand the parameters that limit the grain growth of BZY20, since high grain boundary area compromises the electrical conductivity. This understanding was constructed from SEM microstructure analysis associated with EDS of sintered samples.

A novel Li1/3Sr1/3Eu1/3MoO4 red phosphor: Influences of sintering temperature on microstructures and luminescent properties

A series of novel Li1/3Sr1/3Eu1/3MoO4 phosphors have been fabricated via the conventional ceramic processing route at different sintering temperatures. The crystal structure, morphology and luminescent properties of the as-synthesized phosphors were characterized through X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and photoluminescence (PL), respectively. It is found that the sintering temperature has significant influences on the crystallinity, morphology and luminescent properties of the obtained Li1/3Sr1/3Eu1/3MoO4 phosphors. In the selected sintering temperature range (600–1000 °C), all the obtained Li1/3Sr1/3Eu1/3MoO4 phosphors possess tetragonal scheelite structure, the synthesized phosphors changed gradually from quasi-spherical to polyhedral particles with a size of 1.0–5.0 μm. All the as-synthesized Li1/3Sr1/3Eu1/3MoO4 samples are typical red-emission phosphors, which can emit 591 nm and 615 nm red light under the excitation of 393 nm ultraviolet and 464 nm blue light, respectively. Moreover, the emission intensities of the phosphors firstly increase and then decrease with increasing sintering temperature, reaching the maximum at 800 °C. All the obtained Li1/3Sr1/3Eu1/3MoO4 phosphors displayed a pure red emission, which are promising red phosphors.

Lipon-like Electrolyte Powders Made By Scalable Alternative Processing

Lithium phosphorus oxynitride (Lipon) is the most prominent example of glassy oxynitride electrolytes, which have demonstrated high ionic conductivities, stability over a wide voltage window, and resistance to Li dendrite formation.1Perhaps the greatest drawback of glassy oxynitride electrolytes is that expensive, high-vacuum deposition techniques have been necessary to produce electrolyte compositions with high ionic conductivity (> ~10-6S/cm). High-vacuum deposition techniques have low deposition rates (1 – 50 nm/min, which is less than 0.07 g/hr for Lipon at lab scale) and have only been successfully demonstrated for use in thin film batteries. Alternative processing routes for producing Lipon-like electrolytes could enable their wider usage as electrolytes and ionically conductive additives in commercially viable lithium metal and lithium-ion batteries. We have used scalable alternative processing to produce Lipon-like electrolyte nanopowders at a high throughput (5 g/hr at lab scale). This alternative processing method has successfully produced Lipon-like electrolytes that conventional ceramic and glass processing methods have been unable to produce.2,3 The processed powders have a predominantly amorphous structure (x-ray diffraction), a particle size of ~100 nm (SEM), and a Lipon-like composition (energy dispersive x-ray spectroscopy and inductively coupled plasma optical emission spectroscopy). Neutron pair distribution function analysis has been coupled with ab initiomolecular dynamics to verify that the Lipon-like nanopowders have local atomic structures (0 – 20 Å) that are nearly identical to conventionally sputtered Lipon. Impedance spectroscopy was used to measure the ionic conductivity and activation energy of unsintered Lipon-like nanopowder compacts. While interparticle contact resistance likely dominates these values, the unsintered Lipon-like nanopowder compact still demonstrated an ionic conductivity of 5.3 x 10-7S/cm at room temperature. Acknowledgements The information, data, and work presented herein was funded by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000775. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy. Electron microscopy experiments were conducted at ORNL’s Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Computing resources were provided by the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Brendan Lewis, Rutuja Samant, Dora Cheung, and Bob Herbeck at Buffalo Manufacturing Works aided in the processing of later batches of Lipon-like material. Special thanks to: Brenda Smith, Chelsea Chen, Dale Hensley, and Robert Sacci at Oak Ridge National Laboratory. References 1 Bates, J. B.; Dudney, N. J.; Gruzalski, G. R.; Zuhr, R. A.; Choudhury, A.; Luck, C. F. Sputtering of lithium compounds for preparation of electrolyte films. Solid State Ionics, 1992, 53-56, 647-654. 2 Muñoz, F.; Durán, A.; Pascual, L.; Montagne, L.; Revel, B.; Rodrigues, A. C. M. Increased electrical conductivity of LiPON glasses produced by ammonolysis. Solid State Ionics, 2008, 179, 574-579. 3 Mascaraque, N.; Fierro, J. L. G.; Durán, A.; Muñoz, F. An interpretation for the increase of ionic conductivity by nitrogen incorporation in LiPON oxynitride glasses. Solid State Ionics, 2013,233, 73-79.

Structural, electrical and ferroelectric properties of lithium niobate-bismuth ferrite solid solutions

In this present communication, a polycrystalline lead-free system with composition Bi0.60Li0.40Fe0.60Nb0.40O3 (BLFNO termed further) is synthesized using a cheap conventional ceramic processing route. It featured with resistive, capacitive and dielectric properties of the synthesized composition. Room temperature XRD (X-ray diffraction) technique used to determine the single phase formation, structure and lattice parameters. The SEM micrograph reveals the non-uniform distribution of grains with highly dense grain growth. The complex impedance and modulus technique help to analyze the electrical properties of the sample. The frequency and temperature dependent electrical characteristics occurring in the sample were carried out in a wide temperature (25–500 °C) and frequency (1 kHz-1MHz) range. The Nyquist plot depicts the contribution of both grain and grain boundary effect in the prepared composition. The temperature dependent AC conductivity shows the activation energy for conduction. The frequency dependent electrical modulus and impedance analysis suggest non–Debye type relaxation behavior in the sample.

Tunable UV/blue luminescence in rare-earth free glass-ceramic phosphor

A novel rare-earth (RE) free feldspar glass-ceramic phosphor has been designed by a fast sintering route, following a conventional ceramic process. In this work, it is studied how subtle chemical modifications of structural elements may affect luminescence behaviour in this novel matrix. These cation additions acting as glass network former and as modifiers, 1 wt % of SiO2 and CaCO3 or Na2CO3, respectively, produce a photoluminescence enhancement up to 200%. Whereas, addition of Al2O3, a glass network former, decreases the photoluminescence emission. Raman spectroscopy evinces a correlation between photoluminescence emission and the Al,Si disorder at microscopic scale. These findings open a new challenge in order to obtain larger structural disorder to make this RE free glass-ceramic much more powerful for future optical applications, highlighting for security markers or light emitting glasses. This new phosphor might be considered as a more sustainable and low-cost alternative to RE phosphors.

Low-temperature sintering of (1–x)Pb(Zr0.53Ti0.47)O3–xBiYO3 ceramics with nano-powder for piezo-speaker

(1−x)Pb(Zr0.53Ti0.47)O3−xBiYO3 (PZT–x·BY) ceramics were synthesized by conventional bulk ceramic processing technology with various BiYO3 (BY) doping contents. The maximum values of the piezoelectric properties were obtained in the PZT–0.01BY samples sintered at 1160 °C. After optimizing the composition of the PZT–0.01BY piezoelectrics, the sintering temperature could be lowered down to 1000 °C by applying a nano-powder technique. The maximum values of the piezoelectric properties achieved by this novel process were: d33 of 580 pC/N, kp of 67%, and g33 of 95 mV · m N−1. Finally we fabricated a thick-film piezo-speaker with optimized PZT–0.01BY nano-powders using multi-layered ceramic capacitor processes. The sound pressure level (SPL) of the speaker was analyzed at a distance of 50 cm with a driving voltage of 5 Vrms in the frequency range of 100 Hz–11 kHz. The measured SPLmax was very high at 87 dB, which is superior quality compared with other commercial products.

Binder jetting of ceramics: Powders, binders, printing parameters, equipment, and post-treatment

Abstract Binder jetting is expected to become the universal process for preparing ceramic parts because it can overcome multiple problems, such as the difficulty to prepare complex-shaped ceramic parts and the shrinkage of the sintering process, which appear in conventional ceramic preparation process. This paper introduces principles, steps, and applications of binder jetting printing ceramics. Furthermore, five key factors of binder jetting printing ceramics (powders, binders, printing parameters, equipment, and post-treatment process) have been investigated. Accordingly, effects of powders (including shape, particle size and distribution, and additives), binders (including binding method, droplet-formation mechanism, and droplet-infiltration kinetics), printing parameters (including layer thickness, saturation, solid binder, and printing orientation), equipment, and post-treatment (including de-powdering process, and densification process) on density, roughness, strength, accuracy, and resolution of ceramic parts have been discussed and summarized. This paper provides detailed analysis of techniques and mechanisms of binder jetting of ceramics, giving guidance on how to handle raw materials and select various processing parameters for achieving desired performance.

Temperature-induced phase transition, luminescence and magnetic properties of Eu2(MoO4)3 microcrystal red phosphors

A series of Eu2(MoO4)3 crystals with different crystal structures have been successfully fabricated via a conventional ceramics process under different sintering temperatures. Using X-ray diffraction (XRD), Rietveld refinement, Fourier transform infrared (FT-IR) spectra, scanning electron microscope (SEM), differential thermal analysis (DTA), photoluminescence (PL) and vibrating sample magnetometer (VSM), the microstructures, luminescent and magnetic properties of the as-fabricated Eu2(MoO4)3 crystals have been investigated in detail. XRD, FT-IR and Rietveld refinement results show that the crystal structure of the final Eu2(MoO4)3 crystals can be remarkably influenced by the sintering temperature, exhibiting the phase transformation from tetragonal to monoclinic and then orthorhombic in the region of 600–1000 °C. SEM images manifest the sintering temperature has significantly influence on grain size and dispersity of the samples, although it has negligible effect on their morphology. DTA results confirm that the phase transition temperature for tetragonal to monoclinic and monoclinic to orthorhombic is 624 and 887 °C, respectively. PL results reveal that the excitation and emission intensities of the Eu2(MoO4)3 crystals initially increase and then decrease with increasing sintering temperature, given the maximum at 900 °C. VSM results indicate that all the as-fabricated Eu2(MoO4)3 crystals exhibit paramagnetic property. Our work can offer a simple and effective strategy to adjust the crystal structure of Eu2(MoO4)3 crystals.

Co2O3 and SnO2 doped MnZn ferrites for applications at 3–5 MHz frequencies

Abstract The rapid advancement of modern electronic technology requires MnZn ferrites capable of handling high-frequency signals, offering very low power loss and reasonably high permeability. MnZn ferrites were developed by using the conventional ceramic processing technique and the effects of Co2O3 and SnO2 doping on high-frequency magnetic properties were investigated. Co2O3 and SnO2 co-doping resulted in a sharp decrease of eddy-current loss and residual loss of the MnZn ferrites at 3–5 MHz and improved the temperature characteristics at 20–120 °C. The minimum power losses at 20 °C, 10 mT for 3 MHz and 5 MHz were 20 kW/m3 and 81 kW/m3, while the power losses at 100 °C, 10 mT for 3 MHz and 5 MHz were 60 kW/m3 and 205 kW/m3 respectively. The optimal saturation magnetic flux density and initial permeability were 480 mT and 675 respectively. The cut-off frequency of the sample was 12 MHz, establishing it as an ideal material for high-frequency applications.

Improvement of quality factor of SrTiO3 dielectric ceramics with high dielectric constant using Sm2O3

AbstractThe ceramics with the formula of Sr1−xSm2x/3TiO3 (x = 0‐0.5) were prepared by conventional ceramic process. A single phase of SrTiO3‐type with cubic perovskite structure was found companied with a decrease in crystal volume when x < 0.5, which was confirmed by X‐ray diffraction results and Rietveld refine. At the level of x = 0.5, the sample consisted of two phases of SrTiO3‐type and Sm2Ti2O7. Raman spectra were used to confirm the change of vibration to explain the variation in microwave dielectric properties. The dielectric constant decreased, the quality factor increased, and the temperature coefficient shifted negatively, when the x value increased from 0 to 0.4. When the x value located between 0.3 and 0.4, the ceramics exhibited high dielectric constant of 140‐152, high quality factor (>6000).

Structural evolution, dielectric and ferroelectric properties of (1-x)Bi0.5Na0.5TiO3-xBa0.3Sr0.7TiO3 ceramics

(1 − x)Bi0.5Na0.5TiO3−xBa0.3Sr0.7TiO3 (abbreviated as BNT-BST, x = 0.05 ~ 0.40) was prepared by a conventional ceramic processing method and their structural evolution, dielectric and ferroelectric properties were investigated. The structure of the BNT-BST ceramics changes from phase coexistences of Rhombohedral-Tetragonal (x ≤ 0.10) to Tetragonal-Cubic (x ≥ 0.35), across a dominant Tetragonal phase region (0.15 ≤ x ≤ 0.30). By increasing BST content, the grain size of the BNT-BST ceramics slightly decreases, while the temperature Tm of the maximum dielectric constant gradually goes downward from ~ 250 °C to near room temperature. Meanwhile, with the increase of measuring frequency, the Tm increases for the BNT-BST ceramics with x ≥ 0.15, indicating their relaxor ferroelectric characteristics. Room temperature P-E loop test results show that both coercive field Ec and remnant polarization Pr gradually reduce with the increase of x value for relaxor BNT-BST ceramics. Both high peak dielectric constant (er > 6000 at Tm) and saturated polarization (Ps ~ 30 µC/cm2), as well as tunable remnant polarization Pr are obtained in relaxor BNT-BST ceramics suitable for capacitor candidate materials.

Structural evolution and electrical properties of lead-free (1-x) (K0.4Na0.6)Nb0.96Sb0.04O3-xBa0.1(Bi0.5Na0.5)0.9ZrO3 ceramics

New lead-free piezoelectric ceramic system based on (1-x) (K0.4Na0.6) Nb0.96Sb0.04O3-xBa0.1(Bi0.5Na0.5)0.9ZrO3 was designed and fabricated by using conventional ceramic processing techniques. An investigation was carried out with a focus on the effects of Ba0.1(Bi0.5Na0.5)0.9ZrO3 content on the phase structure, dielectric and piezoelectric properties of the ceramics. It was found that adding Ba0.1(Bi0.5Na0.5)0.9ZrO3 could move the rhombohedral-orthorhombic phase transition temperature upwards and simultaneously shift the orthorhombic-tetragonal phase transition temperature downwards, and thereby resulted in the formation of a rhombohedral-tetragonal phase boundary with 0.045 ≤ x ≤ 0.05. The piezoelectric properties were obviously enhanced for the ceramics with compositions near the rhombohedral-tetragonal phase boundary. Furthermore, an analysis was as well conducted on the main characteristics of the ferroelectric-paraelectric phase transition of the ceramics. Our experimental results suggest that the Ba0.1(Bi0.5Na0.5)0.9ZrO3 is an effective additive for the construction of phase boundaries in (K,Na)NbO3-based ceramics, therefore benefiting the improvement of piezoelectric activity.

Structural, Bulk Permittivity, and Magnetic Properties of Lead-Free Electronic Material: Ba1Bi1Cu1Fe1Ni1Ti3O12

In this report, Ba1Bi1Cu1Fe1Ni1Ti3O12 (BBCFNTO termed further) ceramics were synthesized using a conventional ceramic processing route. The formation of multiple phases has been confirmed from by the XRD pattern at room temperature. The surface micrograph indicates the uniform distribution of grains with distinct grain boundary. The co-relation between the impedance and dielectric parameters was realized by using a phase sensitive meter over a good temperature and frequency range. The temperature- and frequency-dependent dielectric properties are linked to the conduction mechanism. The dielectric constant (K) and loss (tanδ) are increased sharply at high-temperature region, which is expected to be the onset of dipolar relaxation phenomena. The contribution of grain boundary (GBs) and grain (Gs) effects can be identified using the complex impedance spectroscopy. This synthesized material is investigated to model multifunctional devices.