Abstract
The effects of $Nd_2O_3$ addition to $Q{\cdot}f_{0}(GHz)$ ceramics with ${\varepsilon}_r$ of 126, $Q{\cdot}f_{0}(GHz)$ of 2240 and of $68\;ppm/^{\circ}C$ on their microwave properties were investigated. For the addition of 5 wt% $Nd_2O_3$, the dielectric constant (${\varepsilon}_r$) showed maximum value of 131, then decreased with the further addition of $Nd_2O_3$. $Q{\cdot}f_{0}(GHz)$ value was still increased to 3533 with 9 wt% $Nd_2O_3$ addition, it is influenced by densification of grain boundary. With more addition of $Nd_2O_3$ up to 18 wt%, the abnormal grain growth have influence on the decreasing of $Q{\cdot}f_{0}(GHz)$ value. But with the further addition of $Nd_2O_3$ over 25 wt%, the $Q{\cdot}f_{0}(GHz)$ value was again increased by the effect of the second phase ($Nd_2Ti_2O_7$) forming. The temperature coefficient of resonant frequency (${\tau}_f$) was decreased from $+\;68\;ppm/^{\circ}C$ with the addition of $Nd_2O_3$, reached $0\;ppm/^{\circ}C$ at 12 wt% addition, and became negative with the further addition of $Nd_2O_3$. The optimum microwave dielectric properties were obtained for $0.3CaTiO_3-0.7(Li_{1/2}Nd_{1/2})TiO_3$ with 9 wt% $Nd_2O_3$ sintered at $1425^{\circ}C$ for 3 hrs. The dielectric constant (${\varepsilon}_r$), the $Q{\cdot}f_{0}(GHz)$ value, and the temperature coefficient of resonant frequency (${\tau}_f$) were 108, 3533, and $+\;6\;ppm/^{\circ}C$, respectively.
유전율(${\varepsilon}_r$) 126, $Q{\cdot}f_{0}(GHz)$값은 2240, 공진주파수의 온도계수(${\tau}_f$) $+68\;ppm/^{\circ}C$의 특성을 갖는 $0.3CaTiO_3-0.7(Li_{1/2}Nd_{1/2})TiO_3에\;Nd_2O_3$를 첨가하였을 때의 마이크로파 유전특성의 변화에 대해 고찰하였다. 유전율(${\varepsilon}_r$)은 5wt% $Nd_2O_3$ 첨가시 131로 가장높은 값을 나타내었으며, 이후 첨가량이 증가함에 따라 유전율은 감소함을 보였다. $Q{\cdot}f_{0}(GHz)$값은 9wt% $Nd_2O_3$ 첨가시까지 입계의 치밀화 등에 의해 3533까지 증가하다가 이후 l8wt% $Nd_2O_3$첨가시까지는 비정상적 입계성장의 영향으로 감소함을 보이고, 25 wt% 이상 첨가시에는 제2상인 $Nd_2Ti_2O_7$상의 영향으로 다시 증가함을 보였다. 공진주파수의 온도계수($({\tau}_f$)는 $Nd_2O_3$첨가에 따라 최초의 $+68\;ppm/^{\circ}C$에서 30wt% $Nd_2O_3$ 첨가시 $-46\;ppm/^{\circ}C$까지 변화함을 알 수 있었다. $0.3CaTiO_3-0.7(Li_{1/2}Nd_{1/2})TiO_3에\;Nd_2O_3$를 9wt% 첨가하여 $1425^{\circ}C$에서 3시간동안 소결한 시편에서 유전율(${\varepsilon}_r$)은 108, $Q{\cdot}f_{0}(GHz)$값은 3533, 공진주파수의 온도계수(${\varepsilon}_f$)가 $+6\;ppm/^{\circ}C$인 우수한 마이크로파 유전특성을 얻을 수 있었다.
