• Korean Journal of Materials Research
• /
• v.11 no.6
• /
• pp.498-501
• /
• 2001

The effects of MnO$_2$ addition on the piezoelectric properties in 0.9Pb($Mg_{1/3}Nb_{2/3}$)$O_3$-0.1Pb$TiO_3$ relaxor ferroelectrics were studied in the ferroelectricity-dominated temperature range from -4$0^{\circ}C$ to 3$0^{\circ}C$. Dielectric, piezoelectric properties and electric-field- induced strain were examined to clarify the effect of MnO$_2$ addition. As the added amount of MnO$_2$ increase. dielectric and piezoelectric properties of Pb(Mg$_{1/3}$ Nb$_{2/3}$O$_3$ became harder. From the experimental results, it was suggested that Mn behaves as a ferroelectric domain pinning element.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.439-442
• /
• 2004

The effects of sintering additives on the low-temperature sintering and microwave dielectric properties of $Mg_4Nb_2O_9$ dielectric ceramics were studied. When $3{\sim}20wt%$ of $0.242Bi_2O_3-0.758V_2O_5$ was added, the sintering temperature decreased from $1100{\sim}1300^{\circ}C$ to $950^{\circ}C$ and high density was obtained. When $Mg_4Nb_2O_9$ was sintered at $950^{\circ}C$ with 10wt% of sintering additive, the microwave dielectric properties of $Q{\times}f_0\;=\;80.035GHz,\;\epsilon_r\;=\;13.3\;and\;\tau_f\;=\;-12.9\;ppm/^{\circ}C$ were obtained.

• Journal of the Korean Ceramic Society
• /
• v.26 no.2
• /
• pp.249-257
• /
• 1989

Dielectric properties and the stability of the perovskite phase in the Pb(Mg1/3Nb2/3)O3 system have been investigated as a function of amount of BaTiO3 and firing temperature. In the specimens fired at 120$0^{\circ}C$, the pyrochlore phase was eliminated by the addition of 10-15m/o BaTiO3 and also the dielectric constant increased. However, the dielectric constant decreased with further addition of BaTiO3 even though no pyrochlore phase was found to be present. The reducing tendency of the pyrochlore phase decreased with lowering the firing temperature in the system of Pb(Mg1/3Nb2/3)O3 with BaTiO3. Dielectric properties in PMN ceramics were affected by the character of the BaTiO3 rather than the pyrochlore phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.172-173
• /
• 2008

In this study, $0.95(K_{0.5}Na_{0.5})NbO_3$-0.05Li$(Sb_{0.8}Nb_{0.2})O_3$ + $Ag_2O$ + x wt% $MnO_2$ were investigated as a function of the amount of $MnO_2$ addition in order to improve dielectric and piezoelectric properties of Lead-free piezoelectric ceramics. With increasing the amount of $MnO_2$ addition, density and electromechanical coupling factor $(k_p)$ increased up to 0.3wt.% $MnO_2$ and decreased above 0.3wt.% $MnO_2$. At the sintering temperature of 1020 $^{\circ}C$, Electromechanical coupling factor $(k_p)$, density, dielectric constant $({\varepsilon}r)$ and mechanical quality factor $(Q_m)$ of composition ceramics with 0.4wt% $Ag_2O$ addition showed the optimal value of 0.431, 4.33 g/$cm^3$, 820 and 119, respectively.

• Journal of the Korean Ceramic Society
• /
• v.34 no.9
• /
• pp.921-926
• /
• 1997

Two NbCx-C1-x/Y2O3/Ti sputter-coated Al2O3 substrates (L 5.5 cm$\times$W 0.5 cm) were diffusion bonded together using hot press method at 95$0^{\circ}C$ for 3 hours under 1 MPa of applied pressure. 4 points bending tests were used to evaluate the mechanical performance of these precracked laminate beams. Two types of mechanical responses were observed: crack penetration through the interface for x=0.75, 1 and crack deflection into an interface for x=0.25, 0.5. The Al2O3/NbCx-C1-x/Y2O3/Ti system suggested here has been proves to be effective for the thermokinetical stability and tailorability of the interfaces of Al2O3/Ti composites at 95$0^{\circ}C$.

• Korean Journal of Materials Research
• /
• v.5 no.8
• /
• pp.1026-1034
• /
• 1995

It is well known that the addition of CaO-SiO$_2$to Mn-Zn ferrites forms an insulating grain bounary layer with high electrical resistivity. This study investigated the effect of Nb$_2$O$_{5}$ on the electromagnetic properties of high frequency low loss Mn-Zn ferrites. The addition of 300ppm Nb$_2$O$_{5}$ developed an exaggerated grain growth while the addition of CaO-SiO$_2$addition with 200ppm Nb$_2$O$_{5}$ more effectively increased the density than that without Nb$_2$O$_{5}$. The addition of Nb$_2$O$_{5}$ showed the lower power loss below 100 ppm SiO$_2$and the Nb$_2$O$_{5}$-CaO addition lowered the power loss at higher sintering temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.05a
• /
• pp.333-336
• /
• 2005

The reduction behavior of $Nb_2O_5$ in aluminum containing self-reducing briquettes(SRNB) was investigated. The time required for slag/metal equilibrium was estimated as about 20 minutes from the addition of SRNB on to the surface of molten steel. The maximum yield of Nb was expected with the slag composition of $60\%CaO-40\%Al_2O_3$. When $CaCO_3$ was used as a flux, the oxidation loss of Al by $CO_2$ should be compensated, and the chemical equivalent ratio of Al to $Nb_2O_5$ of about 1.43 was required to maximize the yield of Nb.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.7
• /
• pp.718-723
• /
• 2004

Crystal structure of $(Ba-{1-x}La_x)[Mg_\frac{1+x}{3}}Nb_\frac{{2-x}{3}}]O_3$ (BLMN) ceramics with 0\leq1x \geq was investigated using synchrotron X-ray powder diffraction (XRD) and high reso(B $a_{l-x}$L $a_{x}$)[M $g_{(1+x)}$3/N $b_{(2-x)/3}$］ $O_3$lution transmission electron microscopy (HRTEM). When the La content, x, is above 0.1, the 1:2 ordered hexagonal structure found in Ba($Mg_\frac{1}{3}Nb_\frac{2}{3}})O_3$(BMN) was transformed into 1:1 ordered cubic structure. The 1:1 ordered cubic structure was maintained up to x=0.7. When x exceeded 0.7, however, BLMN was transformed into 1:1 ordered structure which has cation displacement and in-phase and anti-phase tilt of octahedra.

• Proceedings of the KIEE Conference
• /
• 2003.07c
• /
• pp.1427-1429
• /
• 2003

The $ZnNb_2O_6$ ceramics with 3wt% CuO were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $1000^{\circ}C{\sim}1075^{\circ}C$ for 3hr. in air. The structural properties were investigated with sintering temperature by XRD and SEM. Also, the microwave dielectric properties were investigated with sintering temperature. Increasing the sintering temperature, the peak of second phase($Cu_3Nb_2O_8$) was increased. In the case of $ZnNb_2O_6$+CuO(3wt%) ceramics sintered at $1025^{\circ}C$ for 3hr, the dielectric constant, quality factor were 21.73, 19.276, respectively.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.974-977
• /
• 1999

PSN-PT 2성분계 압전세라믹스의 상도로부터 유전적, 압전적 특성이 양호한 MPB (Morphotropic phase boundary)부근의 조성을 선택하여 도너 도펀트인 $Nb_{2}O_{5}$와 억셉터 도펀트인 $Fe_{2}O_{3}$를 각각 $0{\sim}0.9wt%$ 첨가하여 유전 및 압전특성을 비교, 연구해보았다. 시편모두 $1250^{\circ}C$ 이상에서 이론밀도의 96%이상의 값을 얻을 수 있었고 상온, 1kHz에서 $Fe_{2}O_{3}$의 경우 0.1wt% 첨가된 시편에서 ${\varepsilon}_r$=2054의 최대 비유전율이 나타났으며, 0.7wt% 첨가된 시편에서는 $tan{\delta}$=0.49%의 최소 유전 손실값을 얻었다. $Fe_{2}O_{3}$가 0.1wt%, 0.3wt%로 첨가되었을 때 각각 $K_p$=58%, Qm=222의 값을 얻을 수 있었다.