Nd변성 티탄산납 세라믹을 이용한 MHz대역 압전공진자 제작

Abstract

Nd의 치환량을 0∼20 at.%범위로 변화시켜 제조한 (Pb₁-₃/₂xNdx)(Ti0.98Mn0.02)O₃세라믹의 재료적 성질과 ?隙幌?성을 살펴보았다. Nd이 첨가되지 않은 Pb(Ti0.98Mn0.02)O₃는 소결성이 불량하고 냉각중에 파괴되는 문제가 발생하였으나 Nd³+ 이 Pb²+를 치환함에 따라 격자이방성이 감소하였고, 소결성도 향상되어 치밀한 미세구조를 얻을 수 있었다. (Pb₁-₃/₂xNdx)(Ti0.98Mn0.02)O₃ 세라믹의 전기기계적 이방성(kt/kp)은 x=0.1일 때 최대를 보였으며, 이는 2가인 Pb 격자점을 3가인 Nd이 치환함에 따라 결정이방성이 감소하지만, Pb-vacancy가 생성되어 분극을 용이하게 되는 두가지 상반된 효과의 결과로 생각된다. (Pb0.85Nd0.1)(Ti0.98Mn0.02)O₃세라믹을 이용하여 두께전단모드 공진자를 제작하였다. 공진자의 두께를 0.3, 0.5mm일 때 기본공진주파수가 각각 2.7, 4.5MHz였으며, 소재의 k15는 0.33이었다. 공진자의 불요파는 전극의 중첩도에 민감한 의존성을 나타내었으며, 전극의 중첩도를 적정화함으로써 실용성이 높은 공진자를 얻을 수 있었다.

Microstructures and piezoelectric properties of (Pb₁-₃/₂xNdx)(Ti0.98Mn0.02)O₃(x=0∼0.2) ceramics have been investigated. Pb(Ti0.98Mn0.02)O₃ showed poor sinterability and cracking on cooling, but the substitution of Nd³+ into Pb²+ sites resulted in dense microstructures with reduced crystallographic anisotropy. Electromechanical anisotropy(kt/kp) showed a maximum value of 10 when x=0.1. This result might be attributed to the counteracting effects that with increasing x, the lattice anisotropy decreases, but the poling process becomes easier due to the increase in Pb-vacancy concentration. Thickness-shear mode resonators were fabricated by using (Pb0.85Nd0.1)(Ti0.98Mn0.02)O₃ ceramics. Fundamental resonant frequencies were 4.5 and 2.7MHz for the resonators with thicknesses of 0.3 and 0.5mm, respectively. By optimizing electrode configuration, we obtained good resonant characteristics enough for practical application.

Microstructures and piezoelectric properties of (Pb₁-₃/₂xNdx)(Ti0.98Mn0.02)O₃(x=0∼0.2) ceramics have been investigated. Pb(Ti0.98Mn0.02)O₃ showed poor sinterability and cracking on cooling, but the substitution of Nd³+ into Pb²+ sites resulted in dense microstructures with reduced crystallographic anisotropy. Electromechanical anisotropy(kt/kp) showed a maximum value of 10 when x=0.1. This result might be attributed to the counteracting effects that with increasing x, the lattice anisotropy decreases, but the poling process becomes easier due to the increase in Pb-vacancy concentration. Thickness-shear mode resonators were fabricated by using (Pb0.85Nd0.1)(Ti0.98Mn0.02)O₃ ceramics. Fundamental resonant frequencies were 4.5 and 2.7MHz for the resonators with thicknesses of 0.3 and 0.5mm, respectively. By optimizing electrode configuration, we obtained good resonant characteristics enough for practical application.