• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.881-885
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• 2001

Kinetics and mechanisms of intermediate phases formation in $Ba(Mg_{1/3}Ta_{2/3})O_3$, obtained by a solid state reaction were studied. $Ba{Ta_2}{O_6}$ and ${Ba_4}{Ta_2}{O_9}$ as intermediate products were first formed at $700^{\circ}C$. $Ba(Mg_{1/3}Ta_{2/3})O_3$ was appeared at $800^{\circ}C$. Several reactions take place on heating process. $Ba{Ta_2}{O_6}$ is found at the first stage of the reaction, and then $Ba{Ta_2}{O_6}$ or ${Ba_4}{Ta_2}{O_9}$ react with MgO to form $Ba(Mg_{1/3}Ta_{2/3})O_3$. The reaction of $Ba(Mg_{1/3}Ta_{2/3})O_3$ formation does not complete until fired at $1350^{\circ}C$ for 60 min. The kinetics of solid-state reaction between powdered reactants was controlled by diffusion mechanism, and can be explained by the Jander's model for three-dimensional diffusion.

• Korean Journal of Materials Research
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• v.16 no.6
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• pp.373-376
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• 2006

[ $Ba(Mg_{1/3}Ta_{2/3})O_3$ ] nanoparticles were synthesized in water solution under mild temperature and pressure conditions by precipitation from $Ba(NO_3),\;Mg(NO_3)_2{\cdot}6H_2O\;and\;TaCl_5$ with aqueous potassium hydroxide. The average size and distribution of the synthesized $Ba(Mg_{1/3}Ta_{2/3})O_3$ nanoparticles were below 100 nm and broad, respectively. The phase of synthesized particles was crystalline reacted at $170^{\circ}C$ for 4 h. The characterization of $Ba(Mg_{1/3}Ta_{2/3})O_3$ nanoparticles were studied using XRD, SEM, and TEM.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1299-1306
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• 1994

Effect of MgO content on microstructural evolution and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 system was investigated. MgO content was varied from 10 mol% deficiency to 10 mol% excess of stoichiometric composition, respectively. It was found that MgO-deficient specimen showed faster grain growth rate than stoichometric and MgO excess BMT system. Besides, sandwich type precipitates of Ba5Ta4O15 which was formed within the BMT grain, might lead to the anisotropic grain growth of BMT grain. On the contrary, in MgO excess specimen, BMT grain growth rate was retarded by precipitations of MgO phase in grain boundary. Besides, the Q values of MgO-deficient showed lower than MgO-excess due to precipitations of Ba5Ta4O15 within BMT grain.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.639-644
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• 1988

The physical and dielectric properties of complex perovskite compound Sr(Mg1/3Nb1/3)O3-Ba(Mg1/3Nb2/3)O3-Ba(Mg1/3Ta2/3)O3(BMT) system were investigated as a function of composition. As the mole ratio of BMN was increased, lattice parameter ratio c/a was slightly increased, and density was increased in SMN-BMN system. However, in BMN-BMT system, lattice parameter ratio c/a and density were decreased with increasing the mole ratio of BMN. Dielectric constant, dielectric loss at $25^{\circ}C$ and 100kHz, and temperature coefficient of resonant frequency, the dependence of temperature in capacitance were increased with increasing the mole ratio of BMN in SMN-BMN-BMT system. These result can be explained according to the degree of order=disorder and dielectric constant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.485-492
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• 2000

The sintering characteristics and the effects of density on dielectric properties in 0.2Ba(Mg$_{1}$3(Nb$_{2}$3/)O$_3$-0.8Ba(Mg$_{1}$3//Ta$_{2}$3/)O$_3$ceramics were investigated. The samples were made by the powder mixing techniques with the two step calcining conditions. When the 1st and the 2nd calcining temperatures were 120$0^{\circ}C$ and the sintering temperature was 155$0^{\circ}C$the density of samples showed the highest value (7.45 g/cm$^3$, 98.5% of theoretical density) among them. The dielectric constant of samples was nearly independent of density but the tan $\delta$ and the temperature coefficient of dielectric constant decreased linearly with increasing of the density. The quality factor(Q$\times$f), the temperature coefficient of resonance frequency and the dielectric constant of Ba[Mg$_{1}$3(Nb$_{0.2}$/Ta$_{0.8}$)sub 2/3/]O$_3$ceramic were 79,548 GHz, +1.5 ppm/$^{\circ}C$ and 26 in the microwave range, respectively.ely.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.175-180
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• 1997

새로운 복합페로브스카이트계 고용체 (1-x)Ba(Mg1/3Ta2/3)O3-xLa(Mg2/3Ta1/3)O3(x=0.0-1.0)를 설계하고 조성에 따른 고용체의 결정구조의 변화 및 MPB(Morphotropic Phase Boundary)를 분말 XRD를 이용하여 분석하였다. 초격자회절선의 변화로부터 MBT에 10mol%의 LMT를 치환함에 따라 1:2에서 1:1로의 규칙화타입의 전이가 일어남을 알 수 있었다. 면심입방정구조 영역(0.10.8조성의 경우, 주회절선의 피이크분리 및 새로운 회절선들로부터 격자비틀림의 형태가 단사정임을 알 수 있었다.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1561-1569
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• 1994

Effect of calcining temperature on the sintering behaviors and microwave dielectric properties of BMT[Ba(Mg1/3Ta2/3)O3] ceramics was studied. The calcining temperatures were varied from 80$0^{\circ}C$ to 130$0^{\circ}C$, respectively. It was found that, as calcining temperature lowered below 125$0^{\circ}C$, second phase such as Ba5Ta4O15 phases started to appear in calcined powder with unreacted powders. After sintering, exaggerately grown Ba5TaO3 phase could be found amang the uniform BMT grains in sintered body. Basis on the infiltration experiment, Ba0.05TaO3 phase should be formed by reaction of BMT grain and BaO-MgO eutectic liquid. But increase of calcining temperature above 125$0^{\circ}C$, there was not any second phase or unreated component in calcined powder and sintered body. As result, low calcining temperature led to precipitation of second phase in specimen and resulted decrease of Q value of BMT ceramics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.84-87
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• 2000

The microwave dielectric properties of complex perovskite-structured $Ba(Mg_{1/3}Ta_{2/3})O_3$ ceramics were investigated with calcining condition. The BMT ceramics were prepared by conventional mixed oxide method. Calcining conditions were $1200^{\circ}C$ for 10hr., $1300^{\circ}C$ for 2hr., and 5hr., respectively. And the specimens were sintered at $1650{\mu}m$. The structural and microwave properties of BMT ceramics were investigated by XRD, SEM and network analyzer. In the case of BMT ceramics calcined at $1300^{\circ}C$ for 5 hr., dielectric constant, quality factor and temperature coefficient of resonant frequency were 20.26, 31,144(at 1GHz), 6.11[ppm/$^{\circ}C$], respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.167-168
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• 2009

Phase pure barium magnesium tantalate $Ba(Mg_{1/3}Ta_{2/3})O_3$(BMT) nanopowders were synthesized at temperature as low as $220^{\circ}C$ through glycothermal reaction by using $Ba(OH)_2{\cdot}8H_2O$, $Mg(NO_3){\cdot}6H_2O$, and $TaCl_5$ as precursors and 1,4-butandiol as solvent. XRD, SEM, and TGA data support that glycothermal processing method provides a simple low temperature route for producing fine grained BMT nanopowders without alkaline mineralizers. BMT nanopowders synthesized at $220^{\circ}C$ showed more homogenous with rounded morphologies.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.3
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• pp.110-114
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• 2001

$0.7Ba(Mg{\frac}_{1}{3}Ta{\frac}_{1}{3})O_3-0.3Ba({\frac}_{1}{3}Nb{\frac}_{1}{3})O_3ceramics$ were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $1500{\sim}1575[^{\circ}C]$ for 5 hours in air. The microwave dielectric properties of the specimens were investigated with sintering temperature. The 0.7BMT-0.3BCN ceramics showed typical XRD patterns of the complex perovskite structure. Dielectric constant and quality factor were increased with increasing the sintering temperature. In the case of the specimens sintered at $1575[^{\circ}C]$ for 5 hours, dielectric constant, quality factor and temperature coefficient of resonant frequency were good values of 28,23545 at 10[㎓] and -1.2 $[ppm/^{\circ}C]$, respectively.