• Applied Chemistry for Engineering
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• v.16 no.5
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• pp.648-652
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• 2005

A super ionic conductor, $K^+$-beta-aluminas, which is known to be difficult to obtain in the form of dense sintered density under atmospheric pressure, was pulverized to 350 nm mean particle size using attrition mill. The sample were pressed into tablet form by uniaxial pressing. The specimen was sintered under atmospheric pressure in powder form. Sintering temperature range was $1400^{\circ}C$ to $1650^{\circ}C$ at $50^{\circ}C$ intervals. Additionally, zone sintering was carried out to control the growth grain at high temperature ($1600^{\circ}C$). The density of specimens that were sintered at $1600^{\circ}C$ and $1650^{\circ}C$, and sintered at $1600^{\circ}C$ by zone sintering were about 93% and 95%, respectively. In the case of the lengthened sintering time to 2 h, the density of specimen was reduced to lower than 90%, since the particles were grown to the duplex microstructure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.90-94
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• 2016

In this work, [$Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_x(Zr_{0.5}Ti_{0.5})_{0.97-x}O_3-BiFeO_3$] (x=0.02 to 0.12) composition ceramics were fabricated by the conventional soild state reaction method and their microstructure and piezoelectric properties were investigated according to PNN substitution. The addition of small amount of $BiFeO_3$, $Li_2CO_3$, and $CaCO_3$ were used in order to decrease the sintering temperature of the ceramics. The XRD (x-ray diffraction patterns) of all ceramics exhibited a perovskite structure. The sinterability of PMW-PNN-PZT-BF ceramics was remarkably improved using liquid phase sintering of $CaCO_3$, $Li_2CO_3$. However, it was identified from of the X-ray diffraction patterns that the secondary phase formed in grain boundaries decreased the piezoelectric properties. According to the substitution of PNN, the crystal structure of ceramics is transformed gradually from a tetragonal to rhombohedral phase. The x=0.10 mol PNN-substituted PMW-PNN-PZT-BF ceramics sintered at $920^{\circ}C$ showed the optimum values of piezoelectric constant($d_{33}$), piezoelectric figure of merit($d_{33{\cdot}}g_{33}$), planar piezoelectric coupling coefficient($k_p$) and density : $d_{33}=566$ [pC/N], $g_{33}=29.28[10^{-3}mV/N]$, $d_{33{\cdot}}g_{33}=16.57[pm^2/N]$, $k_p=0.61$, density=7.82 [$g/cm^3$], suitable for duplex ultrasonic sensor application.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.644-649
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• 1995

The sinterability and the microstructure of Al doped UO$_2$-6wt%Gd$_2$O$_3$pellets, which were doped using Al(OH)$_3$, ADS(aluminium distearate), Al(OH)$_3$+ ADS mixture and sintered at 1$700^{\circ}C$ for 4h in H$_2$, atmospheres, were examined. The sintered densities of Al doped UO$_2$-6wt%Gd$_2$O$_3$pellets were more than 94% T.D.. The open porosity in ADS doped pellets was dramatically decreased. And the amounts of pores less than l${\mu}{\textrm}{m}$ and larger than 10${\mu}{\textrm}{m}$ were decreased regardless of the kinds of doped Al compounds. And the average pore size of Al doped UO$_2$-6wt%Gd$_2$O$_3$pellets was ranged between 2 and 3${\mu}{\textrm}{m}$. While grain structure of non-doped UO$_2$-6wt%Gd$_2$O$_3$pellets was revealed to be duplex type (rocks in sands), that of Al doped pellets to be uniformly equiaxid type. Especially, the grain size in ADS doped pellets was averaged to 4.6${\mu}{\textrm}{m}$.