• Korean Journal of Materials Research
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• v.25 no.1
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• pp.37-42
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• 2015

The effect of sintering temperature on the microstructure, electrical and dielectric properties of (V, Mn, Co, Dy, Bi)-codoped zinc oxide ceramics was investigated in this study. An increase in the sintering temperature increased the average grain size from 4.7 to $10.4{\mu}m$ and decreased the sintered density from 5.47 to $5.37g/cm^3$. As the sintering temperature increased, the breakdown field decreased greatly from 6027 to 1659 V/cm. The ceramics sintered at $900^{\circ}C$ were characterized by the highest nonlinear coefficient (36.2) and the lowest low leakage current density ($36.4{\mu}A/cm^2$). When the sintering temperature increased, the donor concentration of the semiconducting grain increased from $2.49{\times}10^{17}$ to $6.16{\times}10^{17}/cm^3$, and the density of interface state increased from $1.34{\times}10^{12}$ to $1.99{\times}10^{12}/cm^2$. The dielectric constant increased greatly from 412.3 to 1234.8 with increasing sintering temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.2
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• pp.130-134
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• 2007

In this study, in order to. develop the low temperature sintering ceramics for multilayer piezoelectric actuator, PMN-PNN-PZT ceramics using CuO, $Bi_{2}O_{3}\;and\;Li_{2}CO_{3}$ as sintering aids were manufactured with the amount of $WO_{3}$ addition. The ceramics were sintered at $900,\;930,\;960^{\circ}C$, respectively. Thereafter, their microstructural, dielectric and piezoelectric properties were investigated. The $WO_{3}$ was proved to lower the sintering temperature of piezoelectric ceramics due to the effects of PbO and $WO_{3}$ liquid phase. At 0.3 wt% $WO_{3}$ added specimen sintered at $930^{\circ}C$, electromechanical coupling factor($k_{p}$), mechanical quality factor($Q_{m}$), dielectric constant and $d_{33}$ showed the optimum values as the values of 0.60, 1,402, 1,440 and 360 pC/N, respectively, for multilayer piezoelectric actuator application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.397-404
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• 2009

Effects of ceramic filler types and dose on the low temperature sintering and dielectric properties of ceramic/$CaO-Al_2O_3-SiO_2$ (CAS) glass composites were investigated. All of the specimens were sintered at $850{\sim}900^{\circ}C$ for 2 h, which conditions are required by the low-temperature co-firing ceramic (LTCC) technology. Ceramic fillers of $CaCO_3$, $Al_2O_3$, $CaCO_3-Al_2O_3$ mixture, and $CaCO_3-Al_2O_3$ compound ($CaAl_2O_4$), respectively, were used. The addition of $Al_2O_3$ yielded the crystalline phase of alumina, which was associated with the inhibition of sintering, while, $CaCO_3$ resulted in no apparent crystalline phase but the swelling was significant. The additions of $CaCO_3-Al_2O_3$ mixture and $CaAl_2O_4$, respectively, yielded the crystalline phases of alumina and anorthite, and the sintering properties of both composites increased with the increase of filler addition and the sintering temperature. In addition, the $CaAl_2O_4$/CAS glass composite, sintered at $900^{\circ}C$, demonstrated good microwave dielectric properties. In overall, all the investigated fillers of 10 wt% addition, except $CaCO_3$, yielded reasonable sintering (relative density, over 93 %) and low dielectric constant (less than 5.5), demonstrating the feasibility of the investigated composites for the application of the LTCC substrate materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.53-53
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• 2008

Piezoelectric transformers have been widely used such as DC-DC convertor, invertor, Ballast, etc. Because, the y have some merits compared with electro-magnetic transformers such as step-up ratio, high efficiency, small size and lg hit weight, etc. Piezoelectric transformer require high electromechanical coupling factor kp in order to induce a large out put power in proportional to applied electric field. And also, high mechanical quality factor Qm is required to prevent mechanical loss and heat generation. In general, PZT system ceramics should be sintered at high temperatures between 1200 and $1300^{\circ}C$ in order to obtain complete densification. Accordingly, environmental pollution due to its PbO evaporation. Hence, to reduce its sintering temperature, various kinds of material processing methods such as hot pressing, high energy mill, liquid phase sintering, and using ultra fine powder have been performed. Among these methods, liquid phase sintering is basically an effective method for aiding densification at low temperature. In this study, In order to comparis on low temperature sintering and solid state sintering piezoelectric transformers, rosen type transformers were fabricated u sing two PZT ceramics compositions and their electrical properties were investigated.

• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.66-78
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• 1998

the microstructure and mechanical properties of seeded and ball-milled dry gels prepared by boehmite sol-gel method were discussed. The densification of seeded gels was improved with increasing seed content namely the number of seed The number of seed was 1.09, 3.35, 5.72${\times}$1012/cm3 boehmite when seeded with 1, 3, 5wt% respectively The ball milled gel contained about 0.5wt% seed and the number of seed was 4.72${\times}$1012/cm3 boehmite. The sintered density of 5wt% seeded gel was below 80% when sintered at 1300$^{\circ}C$ for 1h. On the other hand that of ball milled gel was very improved and reached to 97% In the case of 3wt% seeded gels the density over 97% was attained when sintered at 1500$^{\circ}C$for 1h. and the grain of the sintered body was several micrometers in size. However the sintered body of ball milled gel showed grain size of submicrometer when sintered at 1300$^{\circ}C$ for 1h. And this specimen showed highest harness value of 1900kg/mm2 The fracture toughness increased with increasing sintering temperature. The sintered body of ball milled gel showed the largest grain size and the highest fracture toughness without regard to sint-ering temperature.

• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.451-456
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• 1991

Electrical properties of 0.15 mol% Y2O3 doped semiconducting BaTiO3 ceramics have been investigated as functions of Pb5Ge3O11 contents (from 0.25 mol% to 2.5 mol%) and sintering temperatures (from 1150$^{\circ}C$ to 1300$^{\circ}C$). The low-temperature sintered BaTiO3 ceramics above 1150$^{\circ}C$ show increase of Curie temperature due to the diffusion of Pb+2 ions, and their PTCR effects decrease. As the sintering temperature increases the room temperature resistance decreases due to the growth of the grain, but the room temperature resistance increases with the increase of the Pb5Ge3O11 contents by the formation of thick insulating layers at the grain boundary.

• Journal of Powder Materials
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• v.24 no.2
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• pp.115-121
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• 2017

In this work, p-type Bi-Sb-Te alloys powders are prepared using gas atomization, a mass production powder preparation method involving rapid solidification. To study the effect of the sintering temperature on the microstructure and thermoelectric properties, gas-atomized powders are consolidated at different temperatures (623, 703, and 743 K) using spark plasma sintering. The crystal structures of the gas-atomized powders and sintered bulks are identified using an X-ray diffraction technique. Texture analysis by electron backscatter diffraction reveals that the grains are randomly oriented in the entire matrix, and no preferred orientation in any unique direction is observed. The hardness values decrease with increasing sintering temperature owing to a decrease in grain size. The conductivity increases gradually with increasing sintering temperature, whereas the Seebeck coefficient decreases owing to increases in the carrier mobility with grain size. The lowest thermal conductivity is obtained for the bulk sintered at a low temperature (603 K), mainly because of its fine-grained microstructure. A peak ZT of 1.06 is achieved for the sample sintered at 703 K owing to its moderate electrical conductivity and sustainable thermal conductivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.290-291
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• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, sensers, transducers, PMN-PNN-PZT ceramics were manufacrtured with the sintering temperature, and their piezoelectric and dielectric properties were investigated. At the composition ceramics sintered at $900^{\circ}C$, desity, dielectric constant$({\varepsilon}_r)$, electromechanical coupling factor(kp), piezoelectric constant$(d_{33})$ and mechanical quality factor(Qm) showed the optimal value of $7.86g/cm^3$, 1417, 0.634, 410pC/N and 1138, respectively.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.158-164
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• 1995

Solid solutions Sr$_{2}$(Ta$_{1-x}$ Nb$_{x}$)$_{2}$O$_{7}$, (x=0.0-1.0), composed of strontium tantalate(Tc=-107.deg. C) and strontium-niobate(Tc=1342.deg. C) were prepared by the conventional mixed oxide method and the flux method(molten salt synthesis method). Phase relation, sintering temperature, grain-orientation and dielectric properties for sintered ceramic samples were investigated with different compositions. Both Curie temperature and dielectric constant at Curie temperature were increased, and sintering behavior and the degree of grain-orientation were improved with the increase of Nb content. The single phase Sr$_{2}$(Ta/sib 1-x/Nb$_{x}$)$_{2}$O$_{7}$ powder was synthesized by using the flux method at lower temperatures, and sintering temperature was also reduced by using the flux method-derived powder than using the mixed oxide-derived powder. Sintering characteristics and dielectric properties of the specimens prepared by the flux method were better than those derived through the conventional mixed oxide method.thod.hod.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.821-825
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• 2004

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PMN-PZT ceramcis using $Li_2CO_3$ and $Bi_2O_3$ as sintering aids were manufactured, and their microstructural, dielectric and piezoelectric properties were investigated. The sintering aids were proved to lower the sintering temperature of piezoelectric ceramics due to the effect of $LiBiO_2$ liquid phase. At 0.1wt% $Li_2CO_3$ added specimen sintered at $970[^{\circ}C]$, electromechanical coupling factor(Kp), mechanical quality factor(Qm) and dielectric constant showed the optimum values of 0.50, 2,413 and 1,245, respectively, for multilayer piezoelectric transformer application.