Bulk Ceramic Processing Research Articles

Thin film growth effects on electrical conductivity in entropy stabilized oxides

Entropy stabilization has garnered significant attention as a new approach to designing novel materials. Much of the work in this area has focused on bulk ceramic processing, leaving entropy-stabilized thin films relatively under-explored. Following an extensive multi-variable investigation of polycrystalline (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O thin films deposited via pulsed laser deposition (PLD), it is shown here that substrate temperature and deposition pressure have strong and repeatable effects on film texture and lattice parameter. Further analysis shows that films deposited at lower temperatures and under lower oxygen chamber pressure are ∼40× less electrically resistive than otherwise identical films grown at higher temperature and pressure. Annealing these films in an oxygen-rich environment increases their electrical resistivity to match that of the films grown at higher temperatures and pressures. Because of this, the electric conductivity is hypothesized to be the result of polaron hopping mediated by transition metal valence changes which compensate for oxygen off-stoichiometry.

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.

Improved Temperature Stability in Dielectric Properties of 0.8BaTiO3-(0.2-x)NaNbO3-xBi(Mg1/2Ti1/2)O3 Relaxors

Ferroelectric relaxor ceramics with BaTiO₃-NaNbO₃-Bi(Mg 1/2 Ti 1/2 )O₃ ternary compositions (BT-NN-BMT) have been prepared by sol-gel powder synthesis and consequent bulk ceramic processing. Through the modified chemical approach, fine and single-phase complex perovskite compositions were successfully obtained. Temperature and frequency dependent dielectric properties indicated typical relaxor characteristics of the BT-NN-BMT compositions. The ferroelectric–paraelectric phase transition became diffusive when NN and BMT were added to form BT based solid solutions. BMT additions to the BT-NN solid solutions affected the high temperature dielectric properties, which might be attributable to the compositional inhomogeneity of the complex perovskite and resulting weak dielectric coupling of the Bi-containing polar nanoregions (PNRs). The temperature stability of the dielectric properties was good enough to satisfy the X9R specification. The quasi-linear P-E response and the temperature- stable dielectric properties imply the high potential of this ceramic compound for use in high temperature capacitors.

The Magnetoelastic Ion: Friend and Foe to Microwaves

From the earliest years of ferrite development, spin-lattice interactions from select transition-metal (3dn) and rare-earth (4fn) ions have influenced key parameters of microwave device performance. Hysteresis loop squareness and coercivity, and magnetic loss that is related to the ferrimagnetic resonance linewidth will continue to depend on cautious inclusion of ions of the 3dn and 4fn series. As the promise of films and layers for planar devices are made more realizable by rapidly advancing deposition technologies, new challenges appear from the presence of stress imparted by mismatches at film/substrate interfaces. To offset unwanted effects of bias strains, increased use of magnetoelastic ions will become necessary. An additional feature made possible by deposition processing at temperatures lower than those of bulk ceramic sintering or melt-grown single crystals is the stabilization of cation valence states that do not normally occur in the thermodynamic equilibrium of conventional bulk ceramic processing. In the future that will undoubtedly involve structures of steadily decreasing dimensions, ferrite applications will have to account for surface compositional variations and interface stress effects. To this end, this article examines the physics that underlies the possible advantages and potential hazards to microwave technologies of the future, where magnetoelastic 3dn ions Mn3+, Fe4+, Fe2+, Co4+, Co2+, and Cu2+, as well as other ions such as Ho3+ or Dy3+ of the 4fn shell can influence the microwave performance.

Effects of CeO<sub>2</sub> on the Piezoelectric Properties of PSN-PMN-PZT Composition under Various Alternating Electric Fields

0.03Pb(Sb0.5Nb0.5)O3-0.03Pb(Mn1/3Nb2/3)O3-(0.94-x)PbTiO3-xPbZrO3 ceramics doped with CeO2 were synthesized by conventional bulk ceramic processing technique. Phases analysis, microstructures and piezoelectric properties were investigated as a function of CeO2 contents (0.03, 0.05, 0.1 0.3, 0.5 and 0.7wt%). Microstructures and phases information were characterized using a scanning electron microscope (SEM) and an X-ray diffractometer (XRD). Relative dielectric constant (K33 T) and coupling factor (kp) were obtained from the resonance measurement method. Both K33 T and kp were shown to reach to the maximum at 0.1wt% CeO2. In order to evaluate the stability of resonance frequency and effective electromechanical coupling factor (Keff) as a function of CeO2 addition under strong electric field, the variation of resonance and anti-resonance frequency were also measured using a high voltage frequency response analyzer(FRA5096) under various alternating electric fields from 10V/mm to 80V/mm. It was shown that effective electromechanical coupling factor was increased by increasing the CeO2 additions.

Effects of Y<sub>2</sub>O<sub>3</sub> on the Piezoelectric Properties of PSN-PMN-PZT Composition under Various Alternating Electric Fields

0.03Pb(Sb0.5Nb0.5)O3-0.03Pb(Mn1/3Nb2/3)O3-(0.94-x)PbTiO3-xPbZrO3 ceramics doped with Y2O3 were synthesized by conventional bulk ceramic processing technique. Phases analysis, microstructures and piezoelectric properties were investigated as a function of Y2O3 contents (0.03, 0.05, 0.1 0.3, 0.5 and 0.7 wt.%). Microstructures and phases information were characterized using a scanning electron microscope (SEM) and an X-ray diffractometer (XRD). Relative dielectric constant (K33 T) and coupling factor (kp) were obtained from the resonance measurement method. Both K33 T and kp were shown to reach to the maximum at 0.1wt.% Y2O3. In order to evaluate the stability of resonance frequency and effective electromechanical coupling factor (Keff) as a function of Y2O3 contents under strong electric field, the variation of resonance and anti-resonance frequency were also measured using a high voltage frequency response analyzer(FRA5096) under various alternating electric fields from 10V/mm to 80V/mm. It was shown that the effective electromechanical coupling factor was stabilized along with increasing Y2O3 contents.

Effects of ZnO on the piezoelectric properties of Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramics

Perovskite-type 0.05 Pb(Mn1/3Sb2/3)O3-0.95 Pb(Zr0.5Ti0.5)O3 (PMS-PZT) was synthesized by conventional bulk ceramic processing technique. ZnO as a dopant up to 0.5 mol% was incorporated into the PMS-PZT system, and the effects on piezoelectric properties were investigated. Pyrochlore phase was not detected to form during the synthesis of the PMS-PZT system with 0∼0.5 mol% ZnO addition. The highest density of 7.92 g/cm3 was obtained when sintered at 1200°C for 2 hrs. Piezoelectric properties as a function of ZnO content were evaluated using a gain phase analyzer. Piezoelectric charge constant (d31) and piezoelectric voltage output coefficient (g31) increased up to −130 pC/N and −24.9 × 103Vm/N, respectively, with increasing ZnO content. Mechanical quality factor (Qm) was shown to reduce considerably with increasing ZnO content. When 0.3 mol% of ZnO was added into the system, electromechanical coupling factor (kp) and relative dielectric constant (\( {\varepsilon ^{T}_{{33}} } \mathord{\left/ {\vphantom {{\varepsilon ^{T}_{{33}} } {\varepsilon _{0} }}} \right. \kern-\nulldelimiterspace} {\varepsilon _{0} } \)) reached to the maximum of 56% and 1,727, respectively.

PSN-PMN-PZT 조성의 CeO2첨가에 따른 압전.유전특성 변화

0.03Pb<TEX>$(Sb_{0.5}Nb_{0.5})O_{3}-0.03Pb(Mn{1/3}Nb{2/3)O_{3}-(0.94-x)PbTiO_{3}-xPbZrO_{3}$</TEX> ceramics doped with <TEX>$CeO_{2}$</TEX> were synthesized by conventional bulk ceramic processing technique. Phases analysis, microstructures and piezoelectric properties were investigated as a function of <TEX>$CeO_{2}$</TEX> content (0.03, 0.05, 0.1 0.3, 0.5 and 0.7 wt%). Microstructures and phases information were characterized using a scanning electron microscope (SEM) and an X-ray diffractometer (XRD). Mechanical quality factor (<TEX>$Q_{m}$</TEX>) and coupling factor(kp) were obtained from the resonance measurement method. Both <TEX>$Q_{m}$</TEX> and <TEX>$k_{p}$</TEX> were shown to reach to the maximum at 0.1 wt% <TEX>$CeO_{2}$</TEX>. In order to evaluate the stability of resonance frequency and effective electromechanical coupling factor (<TEX>$K_{eff}$</TEX>) as a function of <TEX>$CeO_{2}$</TEX>, the variation of resonance and anti-resonance frequency were also measured using a high voltage frequency response analyzer under various alternating electric fields from 10 V/mm to 80 V/mm. It was shown that the stability of resonance frequency and effective electromechanical coupling factor were increased with increasing the <TEX>$CeO_{2}$</TEX> contents.

Energy Efficiency Alloy Design in PSN-PMN-PZT Ceramic System for Piezoelectric Transformer Application

To enhance high power characteristics for piezoelectric transformer, an alloy design approach in PZT base ceramic system was considered. Various Zr/Ti ratio compositions in 0.03Pb(Sb0.5Nb0.5)O3- 0.03Pb(Mn1/3Nb2/3)O3-(0.94-x)PbTiO3-xPbZrO3 (0.445x0.475 mol)[PSN - PMN - PZT] system were synthesized by the conventional bulk ceramic processing technique. To improve high power characteristics at their morphotropic phase boundary (MPB) composition of PSN-PMN-PZT system, various spectra of Zr/Ti ratio were systematically experimented, and their effects on the subsequent piezoelectric properties and dielectric properties for high power piezoelectric transformer application were investigated using an impedance analyzer and a laser vibrometer. Microstructure and phase information were characterized using X-ray diffractometer (XRD) and a scanning electron microscope (SEM). When the Zr/Ti ratios were 0.475/0.465, the mechanical quality factor and electromechanical coupling factor were shown to reach the maximum, indicating that this alloy design can be a feasible composition for high power transformer.

Effects of La&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; on the Piezoelectric Properties of Lead-Free (Bi&lt;sub&gt;0.5&lt;/sub&gt;Na&lt;sub&gt;0.5&lt;/sub&gt;)&lt;sub&gt;0.94&lt;/sub&gt;Ba&lt;sub&gt;0.06&lt;/sub&gt;TiO&lt;sub&gt;3&lt;/sub&gt; Piezoelectric Ceramics

In an approach to acclimate ourselves to the recent ecological consciousness trends, a lead free piezoelectric material, bismuth sodium barium titanate (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT), was considered as an environment-friendly alternative to the PZT system. A perovskite BNBT was synthesized by the conventional bulk ceramic processing technique.La2O3 as a dopant was incorporated into the BNBT system up to 0.025 mol, and the doping effects on subsequent piezoelectric and dielectric properties were systematically investigated. In the case of La2O3 addition, the formation of grain boundary coherency was remarkably increased, and the sintered density was increased with increasing La2O3 contents. Piezoelectric and dielectric properties were shown to have the maximum value at 0.02 mol of La2O3 addition. La3+ ions were believed to act as a softener in the BNBT system and to enhance dielectric and piezoelectric properties in this study.

Energy Efficient Alloy Design in PSN-PMN-PZT Ceramic System for Piezoelectric Transformer Application

In order to enhance energy efficiency in high electric conversion devices such as Power transformers, which need to have high power properties, an alloy design approach in <TEX>$Pb(Zr,Ti)O_3(PZT)$</TEX> base ceramic system was attempted <TEX>$0.03Pb(Sb_{0.5}Nb_{0.5})O_3-0.03Pb(Mn_{1/3}Nb_{2/3})O_3-(0.94-x)PbTiO_3-xPbZrO_3$</TEX>[PSN-PMN- PZT] ceramics were synthesized by conventional bulk ceramic processing technique. To improve power properties, the various Zr/Ti ratio was varied ]lear their morphotropic phase boundary (MPB) composition of PSN-PMN-PZT system and their effects on subsequent piezoelectric and dielectric properties for the transformer application at high power were systematically investigated using an impedance analyzer. Microstructure and phase information were characterized using X-ray diffractometer (XRD), a scanning electron microscope (SEM) and others. When the Zr/Ti ratio was 0.415/0.465, the value of <TEX>$Q_m\;and\;k_p$</TEX> were shown to reach to the maximum, indicating that this alloy design can be a feasible composition :or high power transformer.

Effects of La2O3 on the Piezoelectric Properties of Lead-Free (Bi0.5Na0.5)0.94Ba0.06TiO3 Piezoelectric Ceramics

【A lead free piezoelectric material, bismuth sodium barium titanate $(Bi_{0.5}Na_{0.5})_{0.94}Ba_{0.06}TiO_3$ (BNBT), was considered as an environment-friendly alternatives for the current PZT system. A perovskite BNBT was synthesized by conventional bulk ceramic processing technique. In order to improve piezoelectric properties, $La_2O_3$ as a dopant was incorporated into the BNBT system up to 0.025 moi, ana the effects on subsequent the piezoelectric ana dielectric properties were systematically investigated. With increasing $La_2O_3$ contents, the equilibrium grain shape was remarkably evidenced and sintered density was increased. Piezoelectric and dielectric properties were s]town to have maximum values at the $La_2O_3$ contents of 0.02 mol. $La^{3+}$ ions seemed to act as a softener in the BNBT system and to enhance dielectric and piezoelectric properties in this study. ဤΗ⨀ ሀ老 ? ??邰ʗ⨀ 塨岖⨀ ⁗잖⨀ 頨Ζ⨀ 餂 ?돐 련Η⨀ 䞖⨀ ／ࠀ‮Η⨀ 夂 ?? 䠀 က ᠀ � ??邰ʗ⨀ 適岖⨀ 適?⨀ �Ζ⨀  ?돐 硙잖⨀ 硙䞖⨀ ᠦΗ⨀ ? ?? ⠦Ζ⨀ ? ꠉ Ā᭢合 㔀܀檘 큭ࠁ琇؀ ᭢合 Ā Ā Ā ? � 倦Ζ⨀ ਀ 倦Ζ⨀ 性Ζ⨀ ؀က 性Ζ⨀ 怦Ζ⨀ 搀 怦Ζ⨀】

Synthesis of Bi(FexAl1-x)O3 Thin Films by Pulsed Laser Deposition and Its Structural Characterization

We have been attempting to synthesize perovskite BiAlO3 as a new lead-free piezoelectric material. No indication of the formation of the BiAlO3 phase by the bulk ceramic processing or thin film processing has been obtained. Therefore, we undertook to synthesize a solid solution of BiAlO3 and BiFeO3, which has a stable perovskite structure and contains Bi as a component element. Bi(FexAl1-x)O3 solid solution could not be obtained by bulk ceramic processing. However, we succeeded in the fabrication of single-phase Bi(FexAl1-x)O3 thin films on (001) SrTiO3 substrates by pulsed laser deposition. The crystal structure was revealed to be rhombohedral at x=1 and tetragonal at x=0.9.

Amorphous Si(Al)OC ceramic from polysiloxanes: bulk ceramic processing, crystallization behavior and applications

Here we report on bulk Si–Al–O–C ceramics produced by pyrolysis of commercial poly(methylsilsesquioxane) precursors. Prior to the pyrolysis the precursors were cross-linked with a catalyst, or modified by the sol-gel-technique with an Al-containing alkoxide compound, namely alumatrane. This particular procedure yields amorphous ceramics with various compositions (Si 1.00O 1.60C 0.80, Si 1.00Al 0.04O 1.70C 0.48, Si 1.00Al 0.07O 1.80C 0.49, and Si 1.00Al 0.11O 1.90C 0.49) after thermal decomposition at 1100 °C in Ar depending on the amount of Al-alkoxide used in the polymer reaction synthesis. The as-produced ceramics are amorphous and remain so up to 1300 °C. Phase separation accompanied by densification (1300–1500 °C) and formation of mullite at T > 1600 °C are the stages during heat-treatment. Bulk SiAlOC ceramics are characterized in terms of microstructure and crystallization in the temperature regime ranging from 1100 to 1700 °C. Aluminum-free SiOC forms SiC along with cracking of the bulk compacts. In contrast, the presence of Al in the SiOC matrix forms SiC and mullite and prevents micro cracking at elevated temperatures due to transient viscous sintering. The nano-crystals formed are embedded in an amorphous Si(Al)OC matrix in both cases. Potential application of polysiloxane derived SiOC ceramic in the field of ceramic micro electro mechanical systems (MEMS) is reported.

The Fabrication of High-TC Superconducting Wires, Tapes and Bulk Conductors

ABSTRACTThe results of a UK-based industrial consortium, aimed at the development of high-Tcsuperconducting wires, tapes and bulk conductors, are reviewed. The powder-in-tube method has been used to fabricate 10's of metre lengths of bismuth-based, Ag-clad, single and multi-filamentary wires. Performance highlights include current densities of 23,000Acm-2 [7A] at 77K; (zero field) for 2223 bismuth-based wire and greater than 105Acm-2 [25A] and 104cm-2 at 4.2K, zero field and 15T, respectively, for 2212-based wire. Ag-backed, 2212, tape-cast conductors have carried currents of over 60A [80,000Acnrr-2] at 4.2K; (zero field). Bulk ceramic processing techniques, sol-gel chemistry and plasma-spraying have also been used to fabricate a range of YBCO and bismuth-based components. Currents in excess of 100A have been carried in bulk 2223 bismuth-based samples at 77K.

Evaluating the Chemical Compatibility of Potential Substrate Materials for Bi-Sr-Ca-Cu-O Films

AbstractPotential substrate and buffer layer materials for Bi2Sr2CaCu2Ox (BSCCO) were surveyed using bulk ceramic processing techniques. Of the materials tested, only Ag was inert with respect to BSCCO. MgO slightly degrades the superconducting onset temperature and volume fraction. LaGa03 may be a feasible ceramic substrate for BSCCO, although some reaction appears to occur.

Preparation and Characteristics of Thin Films of Nickel Zinc Ferrite

Thin films of nickel zinc ferrite have been prepared by rf sputtering, onto alumina substrates, at various temperatures. Measurement of remnant magnetisation combined with x-ray spectrographic data, enabled us to optimize conditions for the preparation of reproducible films. Chemical stoichiometry of the films was checked by x-ray probe analysis on a low-angle polished section of a film and by atomic absorption spectrometry on solutions of films in hydrochloric acid. The development of spinel phases in the films was followed using a high temperature x-ray camera. The existence of a wustite phase at the substrate film interface of films deposited onto “cold” substrates suggests that the material is transferred from the target as individual atoms of iron, nickel, and zinc. Stoichiometry of composition is not reached until considerable pre-sputtering has taken place. Films deposited on to cold substrates are amorphous. Considerable energy is required to recombine the individual oxides into a spinel phase. Structural homogeneity is dependent upon heat treatment. A similarity to bulk ceramic processing is indicated.