• Electrical & Electronic Materials
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• v.10 no.6
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• pp.533-540
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• 1997

The microwave dielectric properties of ((P $b_{1-x}$ C $a_{x}$)Zr $O_3$ and (P $b_{0.63}$,C $a_{0.37-x}$ $M_{x}$)Zr $O_3$(M=Mg,Sr) ceramics were investigated. In (P $b_{1-x}$ C $a_{x}$)Zr $O_3$ (X=0.33~0.40) ceramics, high quality factor and small temperature coefficient of resonant frequency were obtain in (P $b_{0.63}$C $a_{0.37}$)Zr $O_3$with perovskite structure. In the case of (P $b_{0.63}$C $a_{0.37-x}$M $g_{x}$)Zr $O_3$ dielectric constant temperature coefficient of resonant frequency increased and quality factor decreased due to increase of polarization of A-O bonding. When replacing Ca ion with Sr ion with large ion radius, polarization decreased with increased of bonding length and thus dielectric constant and temperature coefficient of resonant frequency decreased.decreased.creased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.2
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• pp.80-84
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• 2015

We investigated the dielectric relaxation properties $0.5Ba(Zr_{0.2}Ti_{0.8})O_3-0.5(Ba_{0.7}Ca_{0.3})TiO_3$ ceramics with CuO addition. With increasing CuO addition, the lattice parameter was increased by substitution of small amount $Cu^{2+}$ ion in B-site of $0.5Ba(Zr_{0.2}Ti_{0.8})O_3-0.5(Ba_{0.7}Ca_{0.3})TiO_3$ ceramics. Also the grain size and the maximum dielectric constant of $0.5Ba(Zr_{0.2}Ti_{0.8})O_3-0.5(Ba_{0.7}Ca_{0.3})TiO_3$ ceramics was decreased with increasing amounts of CuO addition. Moreover, the diffused phase transition properties (${\gamma}$) of $0.5Ba(Zr_{0.2}Ti_{0.8})O_3-0.5(Ba_{0.7}Ca_{0.3})TiO_3$ ceramics was increased by compositional fluctuation with increasing of CuO amount, changed from 1.45 at 1 wt% CuO addition to 1.94 at 7 wt% CuO addition.

• Proceedings of the Membrane Society of Korea Conference
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• 1992.04a
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• pp.60-60
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• 1992

알루미나 분리막이 세라믹 분리막의 연구개발 초기단계부터 많은 사람들에 의해 연구되어온 반면, TiO$_2$ 및 ZrO$_2$ 분리막에 관한 연구는 상대적으로 관심이 적었고 따라서 그 내화학성및 투과특성의 우수함이 밝혀진 것도 최근의 일이다. TiO$_2$ 및 ZrO$_2$ UF 분리막의 제조방법으로는 $Al_2O_3$ 의 경우와 마찬가지로 대부분 졸-겔 공정이 이용되고 있다.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2361-2367
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• 2010

$TiO_2-ZrO_2$ was prepared with surfactant through a sol-gel method. Catalysts containing 5 - 35% $H_3PO_4$ were prepared using these oxides. Subsequently the catalytic performance of prepared catalysts was determined for liquid phase esterification of aromatic acids. $H_3PO_4/TiO_2-ZrO_2$ has been used as catalyst to synthesize various novel esters by esterification of some aromatic acids with aliphatic alcohols (2-propanol, 1-butanol, iso butanol, 3-pentanol, 1-hexanol, heptanol, cyclo heptanol, octanol and decanol). Under optimized conditions, maximum yields and selectivity (100%) to the corresponding ester, was obtained by using 25 wt % $H_3PO_4/TiO_2-ZrO_2$ as catalyst. The Catalyst can be easily recycled after reaction and can be reused without any significant loss of activity/selectivity performance. No by-product formation, high yields, short reaction times, mild reaction conditions, operational simplicity with reusability of the catalyst are the salient features of the present synthetic protocol. The reaction was carried out under solvent-free condition.

• Journal of the Korean Chemical Society
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• v.29 no.6
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• pp.608-614
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• 1985

Electrical conductivities of $ZrO_2-Sm_2O_3$ systems containing 10, 20, 30, 40, and 50 mol% of $ZrO_2$ have been measured as a function of temperature and of oxygen partial pressure at temperature from 500 to 1000${\circ}C$ and oxygen partial pressures from 1 ${\times}10^{-5}to 1{\times}10^{-1}$ atm. Plots of log conductivity vs. 1/T are found to be linear with an inflection point at around 650$^{\circ}C$ and the temperature dependence of conductivity shows two different defect structures. The conductivities are increased with increasing pressure, slowing a p-type character. The electrical conductivity dependences on $Po_2$ are found to be ${\sigma}{\propto}Po_2^{1/5.3}$ at 650∼1000$^{\circ}C$ and ${\sigma}{\propto}Po_2^{1/6}$ at 500∼650$^{\circ}C$, respectively, The defect structures are Oi" at 650-1000$^{\circ}C$ and $Vs_m$"' at 500-650$^{\circ}C$. The electron hole is main carrier type, however ionic contribution is found at low temperature portion. Ionic contributions increased with the increasing amount of $ZrO_2$ dopant. In 60mol% $ZrO_2-Sm_2O_3$ system, the conductivity is increased with decreasing oxygen pressure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.563-567
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• 2011

The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of $0.96(K_{0.5}Na_{0.5})NbO_3-0.04SrZrO_3+x$ mol% $ZrO_2$ [KNN-SZ+$xZrO_2$; x= 0~0.10] doped with 0.1 wt% $MnO_2$ by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%$H_2-97%N_2$ atmosphere at $1,140^{\circ}C$ exhibit pure perovskite structure irrespective of the content of $ZrO_2$. Meanwhile, the sintering denisty and piezoelectric properties such as $K_p$, $Q_m$ and $d_{33}$ of KNN-SZ samples as a function of $ZrO_2$ content show the maxima ($k_p$=28.07%, $Q_m$= 101.34, $d_{33}$= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+$xZrO_2$ composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.1-6
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• 1996

A single phase Ba2(Ti8,472Zr0.528)O20 was prepared by the oxalate method from aqueous solution of BaCl2 TiCl4 and ZrOCl2. The structure ananlysis has been carried out by Rietveld analysis method at room temperature. Powder X-ray data of Ba2(Ti8,472Zr0.528)O20 was indexed with the triclinic lattice(a=7.4587 $\AA$ b=14.0672 $\AA$, c=13.3327 $\AA$, $\alpha$=89.87, $\beta$=79.45 ${\gamma}$=84.46) The R (Residual) values of structure refinement were in a range between 10.00 and 8.00 This analysis proved that the added Zr occupied Ti sites in th structure of Ba2Ti9O20. Ba2(Ti8,472Zr0.528)O20 has excellent dielectric properties(dielectric constant K=40.49 at 5.42 GHz Q=4621) so that it can be used as good microwave dielectric materials.

• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.53-58
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• 2007

In the dehydrogenation of ethylbenzene to styrene, CO2 could play a role as an oxidant to increase conversion of ethylbenzene and stability as well over TiO2-ZrO2 mixed oxide catalysts. TiO2-ZrO2 catalysts were prepared by co-precipitation method and were characterized by BET surface area, bulk density, X-ray diffraction, temperature programmed desorption of NH3 and CO2. These catalysts were found to be X-ray amorphous with enhanced surface areas and acid-base properties both in number and strength when compared to the respective oxides (TiO2 and CO2). These catalysts were found to be highly active (> 50% conversion), selective (> 98%) and catalytically stable (10 h of time-on-stream) at 600 oC for the dehydrogenation of ethylbenzene to styrene. However, in the nitrogen stream, both activity and stability were rather lower than those in the stream with CO2. The TiO2-ZrO2 catalysts were catalytically superior to the simple oxide catalysts such as TiO2 and ZrO2. The synergistic effect of CO2 has clearly been observed in directing the product selectivity and prolonging catalytic activity.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1147-1161
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• 1995

When ceramic membrance was made from metal salt solution in place of metal akoxide solution, crack free and good adhesion to supporter was optimized for sol stability and good adhesion force. A starting sol was prepared from aluminum oxychloride aqueous solutjion in order to inhibit the grain growthof Al2O3 during heat treatment. The crack free dip coating can't be achieved in 1mol/ι zirconium oxychloride solution because of the high viscosity which interferes with the hydration copolymerization between Al3+ ion and Zr4+ ion. Thus Al2O3-ZrO2 sol stability and viscosity for dip coating was effective when 0.01 mol/ι zirconium oxychloride was added. The minimizing of crack and achieving better adhesion to the supporter wa obtained by microwave drying, surfactant addition and ultrasonic dip coating in wet atmosphere. The result seems to minimize the capillary force and improve the adhesive ability to supporter during the process. Where the average pore size of Al2O3-ZrO2 ultrafilter ceramic membrane measured 17 Å by the BET method and observed γ-Al2O3 phase with tetragonal zirconia after firing at 700℃.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.48-53
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• 2000

This study was aimed at observing the influence of laser irradiation on a $ZrO_2-8%Y_2O_3$ ceramic coating layer fabricated by plasma spraying. The $ZrO_2-8%Y_2O_3$ ceramic powder was plasma sprayed onto SS400 carbon steel substrate and laser irradiated on the coating layer under various conditions of laser power and beam diameters. As to the as-sprayed specimen and laser-treated specimen, a hardness test and a microstructure analysis were performed. Hardness was measured by a microhardness tester; microstructure was observed by an optical microscope and a scanning electron microscope. The result was that the microstructure of the laser-irradiated coating layer was dense; porosities almost disappeared and hardness increased. It was also observed that microcracks occured in the laser-irradiated coating layer.