BNKT Ceramics, one of the representative Pb free based piezoelectric ceramics, constitutes a perovskite(ABO3) structure. At this time, the perovskite structure (ABO3) is in the form where the corners of the octahedrons are connected, and in the unit cell, two ions, A and B, are cations, A ion is located at the body center, B ion is located at each corner, and an anion O is located at the center of each side. Since Bi, Na, and K sources constituting the A site are highly volatile at a sintering temperature of 1100℃ or higher, it is difficult to maintain uniformity of the composition. In order to solve this problem, there should be suppression of volatilization of the A site material or additional compensation of the volatilized. In this study, the basic composition of BNKT Ceramics was set to Bi0.5(Na0.78K0.22)0.5TiO3 (= BNKT), and volatile site (Bi, Na, and K sources) were coated in the form of a shell to compensate additionally for the A site ions. In addition, the physical and electrical properties of BNKT and its coated with shell additives(= @BNK) were compared and analyzed, respectively. As a result of analyzing the crystal structure through XRD, both BNKT(Core) and @BNK(Shell) had perovskite phases, and the crystallinity was almost similar. Although the Curie temperature of the two sintered bodies was almost the same (TC = 290 ~ 300 ℃), it was confirmed that the d33 (piezoelectric coefficient) and Pr (residual polarization) values were different. The experimental results indicated that the additional compensation for a shell additive causes the coarsening, resulting in a decrease in sintering density and Pr(remanent polarization). However, coating shell additives to compensate for A site ion is an effective way to suppress volatilization. Based on these experimental results, it would be the biggest advantage to develop an eco-friendly material (Lead-free) that replaced lead (Pb), which is harmful to the human body. This lead-free piezoelectric material can be applied to a biomedical device or products(ex. earphones (hearing aids), heart rate monitors, ultrasonic vibrators, etc.) and skin beauty improvement products (mask packs for whitening and wrinkle improvement).

In existing ceramic mold manufacturing processes, inorganic binder systems (Si-Na, two-component system) are applied to ensure the effective firing strength of the ceramic mold and core. These inorganic binder systems makes it possible to manufacture a ceramic mold and core with high dimensional stability and effective strength. However, as in general sand casting processes, when molten metal is injected at room temperature, there is a limit to the production of thin or complex castings due to reduced fluidity caused by the rapid cooling of the molten metal. In addition, because sodium silicate generated through the vitrification reaction of the inorganic binder is converted into a liquid phase at a temperature of 1,000 °C. or higher, it is somewhat difficult to manufacture parts through high-temperature casting. Therefore, in this study, a high-strength ceramic mold and core test piece with effective strength at high temperature was produced by applying a Si-Na-Ti three-component inorganic binder. The starting particles were coated with binary and ternary inorganic binders and mixed with an organic binder to prepare a molded body, and then heat-treated at 1,000/1,350/1,500 °C to prepare a fired body. In the sample where the two-component inorganic binder was applied, the glass was liquefied at a temperature of 1,000 °C or higher, and the strength decreased. However, the firing strength of the ceramic mold sample containing the three-component inorganic binder was improved, and it was confirmed that it was possible to manufacture a ceramic mold and core via high temperature casting.

수용성 매체에서 젤-케스팅 공정을 이용하여 용융실리카를 기본으로 하는 다성분계 세라믹 코어 (中子)를 제조하고, 소결조건에 따른 제반 기계적 물성과 알칼리 부식용액에 의한 용출특성을 고찰하였다. 1000cP (at 50sec-1 ) 이하의 낮은 점도를 갖는 50vol%의 고농도 다성분계 세라믹 슬림의 제조가 가능하였다. 성형체는 안정화시킨 슬림을 몰드에 부어 상온에서 겔화시킨 후 25˚C, 80% 상대습도 분위기 하에서 48시간동안 건조시켜 제조하였으며 건조된 성형체에는 균열이 발생하지 않았다. 세라믹 코어 성형체의 소결온도가 상승할 수록 상온강도, 겉보기 밀도, 수축률은 시편의 기공도와 역비례하여 증가하였다. 세라믹 코어 소결체의 용출속도는 동일한 온도에서 알칼리 부식용액의 농도에 의존하였으며, 소결체의 기공도가 클수록 증가하였다.

수용액 매체에서 젤케스팅을 이용하여 복잡한 형상의 세라믹스를 제조하기 위한 새로운 공정을 연구하였다 용융실리카 분말과 첨가제로서 지르콘과 코디어라이트 조성으로 혼합된 현탁액을 electrosteric 방법으로 안정화시켰다. 슬립은 다성분계 세라믹 현탁액에 단량체, 이량체 그러고 분산제를 혼합하고, 볼밀하여 준비하였다. 슬립의 유동학적 특성을 평가하기 위해 점도를 측정하였으며 , 낮은 점도를 갖는 50vo1%의 고농도 다성분계 세라믹 슬립의 제조가 가능하였다. 슬립의 점도는 고분자 분산제의 함량과 단량체 및 이량체의 혼합비에 크게 의존하였다. 성형체는 안정화시킨 슬립을 몰드에 부어 상온에서 젤화시킨 후 25˚C, 80~85% 상대습도 분위기 하에서 48시간동안 건조시켜 제조하였으며 건조된 성형체에는 균열이 발생하지 않았다