• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.12
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• pp.979-986
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• 2001

This paper was researched the effect of slurry stability on the mechanical and electrical property of the porcelain insulator with various raw materials such as feldspar, quartz, clay and l7wt% alumina. The slurry was fabricated after ball milling the mixed raw materials. Green compacts were made by the extrusion and were sintered at 1300$\^{C}$ for 60min in the tunnel kiln. All of the specimens were densified 96% of the theoretical density. The 3-point flexural strength($\sigma$$\_$B/) of the specimen stabilized slurry pH 7.8 was 1650 k9/㎠ and the vickers hardness(Hv) and the fracture toughness(K$\_$IC/) were 27.5 GPa and 2.2 MPa$.$m$\^$$\sfrac{1}{2}$/, respectively. The mechanical properties of the specimen stabilized slurry PH 9.3 were 1716 kg/㎠($\sigma$$\_$B/), 27.6 GPa(Hv) and 3.0 MPa$.$m$\^$$\sfrac{1}{2}$/(K$\_$IC/), respectively. The dielectric strength was increased from 8.3kV/mm to 13.2kV/mm as the increase of the slurry pH from 7.8 to 9.3. Therefore the physical properties of the specimen stabilized slurry pH 9.3 were improved.

• Journal of Surface Science and Engineering
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• v.41 no.4
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• pp.142-146
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• 2008

Trivalent ions(Ga, Al, In) doped ZnO films were deposited by DC magnetron sputtering on non-alkali glass substrate at substrate temperature of $300^{\circ}C$. We used the different three types of high density($95%{\sim}$) ceramic sintered disks(doped with $Ga_2O_3$; 6.65 wt%, $Al_2O_3$; 3.0 wt%, $In_2O_3$; 9.54 wt%). This study examined the effect of different dopants(Ga, Al, In) on the electrical, structural, and optical properties of the films. The lowest resistivity of $5.14{\times}10^{-4}{\Omega}cm$ and the highest optical band gap of 3.74 eV were obtained by Ga doped ZnO(GZO) film. All the films had a preferred orientation along the(002) direction, indicating that the growth orientation has a c-axis perpendicular to the substrate surface. The average transmittance of the films was more than 85% in the visible range.

• Journal of Powder Materials
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• v.17 no.5
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• pp.404-408
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• 2010

The effects of high energy ball-milling (HEBM) on the sintering behavior and piezoelectric properties of 0.1 wt% $Li_2CO_3$ doped 0.8Pb($Mg_{1/3}Nb_{2/3}$)$O_3$-0.2Pb($Zr_{0.475}Ti_{0.525}$)$O_3$ (PMN-PZT) ceramics were investigated. It was found that HEBM treatment was quite effective to reduce the average particle size down to 300 nm, leading to increased density as well as enhanced piezoelectric properties of a sintered specimen even though prolonged HEBM resulted in unwanted secondary phases that caused a degradation of piezoelectric properties. The dielectric constant ($\varepsilon_r$), piezoelectric coupling factor ($k_p$) and piezoelectric constant $d_{33}$ of 0.1 wt% $Li_2CO_3$ doped PMN-PZT ceramics prepared via HEBM for 10 h reached 2040, 0.68 and 554 pC/N, respectively.

• Journal of Powder Materials
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• v.2 no.3
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• pp.223-230
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• 1995

The effects of Mn and Co additions up to 0.6 and 2.0 wt% respectively and the amount of cold-rolled reduction on the thermal expansion coefficient (TEC) of powder rolled Fe-Ni Invar strips were investigated. The compacted strips were sintered, homogenized and cold-rolled to the final thickness of 0.8 mm, 0.65 mm and 0.4 mm. All the strips reached full density except the case of 0.8 mm sample which has a very few porosities. The interstitials which are well known to increase TEC were minimized to the level of 10 rpm C,5 and N,0 by the processing. TEC was found to decrease by increasing the cold reduction. The Mn content had little effect on the TEC. But in Fe-Ni-Co system, TEC decreased with Co content up to 0.4 wt% and then increased, yielding the minimum value of $0.2 {\times} 10-6/^{\circ}C$ at 0.4 wt% Co. This value is much lower than that of commercial Invar product. Such effect of Co is considered to be related with the maxiumum spontaneous- magnetostriction effect.

• Journal of Powder Materials
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• v.13 no.2 s.55
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• pp.129-137
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• 2006

In this study, high purity fine $BaTiO_3$ powders were prepared by SHS (Self-propagating High-temperature Synthesis). We would examinate the study of sintering properties and characteristics as a function of temperature with various additives (binder, sintering agent). In separately binder addition, the green and sintered density of specimen were increased as binder content increases. The increased porosity resulted in fine grain size due to the inhibition of grain boundary moving. The $Al_{2}O_{3},\;TiO_{2}$ and MgO playa role of increasing dielectric constants at room temperature. These values were decreased at curie temperature. In case of $SiO_2$, the Curie temperature was decreased. In this study, a high dielectric ceramic capacitor material with temperature stability was synthesized by using various additives.

• Journal of Powder Materials
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• v.27 no.5
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• pp.373-380
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• 2020

The purpose of this study is to investigate the densification behavior and the corresponding microstructural evolution of tantalum and tantalum-tungsten alloy powders for explosively formed liners. The inherent inhomogeneous microstructures of tantalum manufactured by an ingot metallurgy might degrade the capability of the warhead. Therefore, to overcome such drawbacks, powder metallurgy was incorporated into the near-net shape process in this study. Spark plasma-sintered tantalum and its alloys with finer particle sizes exhibited higher densities and lower grain sizes. However, they were contaminated from the graphite mold during sintering. Higher compaction pressures in die and isostatic compaction techniques also enhanced the sinterability of the tantalum powders; however, a full densification could not be achieved. On the other hand, the powders exhibited full densification after being subjected to hot isostatic pressing over two times. Consequently, it was found that the hot isostatic-pressed tantalum might exhibit a lower grain size and a higher density as compared to those obtained in previous studies.

• Journal of the Korean Ceramic Society
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• v.42 no.1
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• pp.33-36
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• 2005

Effect of heating rate was studied on consolidation of the low-temperature-sinterable PMN-PT-BT powder by varying the heating rate from 5, 10, to $20^{circ}C/min$. Slow rate of $5^{circ}C/min$ showed more homogeneous microstructure than high rate of 10 or $20^{circ}C/min$ due to low PbO (m.p. $886^{circ}C$) evaporation at 850^{circ}C$. It showed sintered density of $7.93 g/cm^{3}$, room temperature dielectric constant of 15300, and dissipation factor of $0.92\%$.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.681-687
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• 2008

The sintering and electrical properties of the hydrothermal PSZT powders obtained by substituting 4, 6 and 8mol% Sr for Pb in PZT lattice structure were investigated. The lattice constant and particle size decreased in proportion to a quantity of Sr. The sintering properties of PSZT powders showed $7.754g/cm^3$ of sintered density and $4{\mu}m$ of grain size at sintering temperature of $1250^{\circ}C$. Curie temperature lowered gradually from $363.6^{\circ}C\;to\;319.2^{\circ}C$ and relative dielectric constants increased rapidly by a quantity of Sr. In comparison to PZT, moreover, the quality factor of PSZT was increased more than three times with increase of Sr mole ratio, and piezoelectric constant $(d_{31}\;and\;g_{31})$ was decreased. It was found that dielectric loss of PSZT was decreased by 0.574% which was half of PZT.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.33-38
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• 2003

Highly homogeneous PZT powder was prepared by a partial oxalate method using chemicals of (Z $r_{0.53}$ $Ti_{0.47}$) $O_2$, Pb(N $o_3$)$_2$and (COOH)$_2$ㆍ2$H_2O$. N $b_2$ $O_{5}$ addition effect on microstructure and electrical properties of PZT ceramics was investigated. When the precursors were calcined at 71$0^{\circ}C$, a single perovskite phase was obtained. After sintering at 110$0^{\circ}C$, X-ray diffraction Patterns showed coexistence of rhombohedral and tetragonal phases regardless of the N $b_2$ $O_{5}$ content. As the content of N $b_2$ $O_{5}$ increased, grain size decreased but sintered density increased. The electromechanical coupling factor of kp and the piezoelectric constant of $d_{31}$ increased linearly with the content of N $b_2$ $O_{5}$, and those values reached 0.7 and -200, respectively, when 1.2 mol% of N $b_2$ $O_{5}$ is added. is added.ded.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.83-91
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• 1996

Monolithic AlN and AlN-W composites were fabricated by pressure-less sintering at 190$0^{\circ}C$ under nitrogen atmosphere and the influences of tungsten phase on the microstructure and mechanical properties were investi-gated. In the fabrication of sintered specimen no additive was used. And monolithic AlN showed substantial grain growth and low relative density. AlN-W composites were fully densified and grain growths of matrix were inhibited. The densification behavior of composites were inferred to be achieved through the liquid phase sintering process such as particle-rearrangement and solutino-reprecipitation. Also the oxid phases which is expected to form liquid phases duringsintering process were detected by XRD analysis. As the tungsten volume content increases fracture strength was decreased and fracture toughness was increased. It was suppo-sed that the strength decrease of composites with tungsten content was due to existence of interface phases. The subcritical crack growth behavior was observed from the stress-strain curve of composites. The effect of the secondary phase and interface phases on toughness in crease were studied through observation of crack propagation path and the influence of residual stress on crack propagation was investigated by X-ray residual stress measurement. In the result of residual stress measurement the compressive stress of matrix in composi-test was increased with tungsten volume content and the compressive stress distribution of matrix must have contributed to the inhibition of crack propagation.