Piezoelectric ceramic specimens with the Pb(Mg1/3Nb2/3)0.65Ti0.35O3 (PMN-PT) composition are prepared by the solid state reaction method known as the “columbite precursor” method. Moreover, the effects of the Li2O-Bi2O3 additive on the microstructure, crystal structure, and piezoelectric properties of sintered PMN-PT ceramic samples are investigated. The addition of Li2O-Bi2O3 lowers the sintering temperature from 1,200oC to 950oC. Moreover, with the addition of >5 wt.% additive, the crystal structure changes from tetragonal to rhombohedral. Notably, the sample with 3 wt.% additive exhibits excellent piezoelectric properties (d33 = 596 pC/N and Kp = 57%) and a sintered density of 7.92 g/cm3 after sintering at 950oC. In addition, the sample exhibits a curie temperature of 138.6oC at 1 kHz. Finally, the compatibility of the sample with a Cu electrode is examined, because the energy-dispersive X-ray spectroscopy data indicate the absence of interdiffusion between Cu and the ceramic material.

The domain structures of annealed (001)-oriented Pb(Mg1/3Nb2/3)O3-x%PbTiO3 (PMN-x%PT) crystals for x = 10, 20, 30, 35, and 40 at% were investigated by Polarized Optical Microscopy (POM) and Scanning Force Microscopy (SFM) in the piezoresponse mode. Both Polar Nano-Domains (PND) and long strip-like domains were clearly observed. The results also showed how the domain structure changed between phases with an increasing x in the PMN-x%PT crystals and the domain hierarchy on various length scales ranging from 40 nm to 0.1 mm. Distorted pseudo-cubic phase (x< 20%) consisted of PNDs that did not self-assemble into macro-domain plates. The rhombohedral phase (x = 30%) consisted of PNDs that began to self-assemble into colonies along preferred 110 planes. The monoclinic phase (x = 35%) consisted of miniature polar domains on the nm scale, whereas, the tetragonal phase (x = 40%) consisted of 001 oriented lamella domains on the mm scale that had internal nano-scale heterogeneities, which self-assembled into macro-domain plates oriented along 001 the mm scale.

Organic binders are usually pre-mixed with ceramic powders to enhance the formability during the shape forming process. These binders, however, must be eliminated before sintering in order to avoid pore formation and unusual grain growth during sintering. The present work was performed to investigate the effects of residual binder on grain growth behavior during sintering of piezoelectric ceramics. The microstructures of sintered samples were examined for various thermal processes and atmosphere at debinding. Addition of binder seems to promote abnormal grain growth especially in incompletely debinded regions and to make the grain shape change from corner-rounded to faceted.

In order to fabricate complex-shaped polycrystalline ceramics by sintering, organic binders are usually pre-mixed with ceramic powders to enhance the formability during the shape forming process. These organic binders, however, must be eliminated before sintering so as to eliminate the possibilities of poor densification and unusual grain growth during sintering. The present work studies the effect of binder addition on grain growth behavior during sintering of piezoelectric ceramics. The microstructures of the sintered samples were examined for various heating profiles and debinding schedules of the binder removal process. Addition of Polyvinyl butyral(PVB) binder promoted abnormal grain growth especially in incompletely debinded regions. Residual carbon appears to change the grain shape from comer-rounded to faceted and enhance abnormal grain growth

완화형 강유전체인 0.9MPb*Mg13/Nb23/)O3-0.1PbTiO3에서 강유전-상유전 상전이에 수반되는 relaxation거동을 살펴보기위해 낮은 전계에서 측정된 유전특성과 높은 전계에서 측정된 전계유기 분극 거동 등을 조사하였다. -50-90˚C의 상전이 온도범위에 걸쳐 1V/mm의 낮은 전계에서 측정된 유전특성의 온도의존성을 구하고 수 kVmm의 강전계하에서 발생된 분극의 온도의존성을 관찰하였다. 이 모든 결과들은 Vogel-Fulcher관계식에 비교적 정확하게 일치되었으며 그 결과 Tf 는 294.6˚K로 나타났다. 본 연구결과를 통하여 Vogel-Fulcher관계식에 의한 주파수 의존성은 낮은 전계하에서의 유전특성 뿐 아니라 강전계하에서의 여러물성들도 동일하게 적용되는 것을 확인할 수 있었다.