Dong-Jin Shin

Ag-migration effects on the metastable phase in CaCu 3 Ti 4 O 12 capacitors

The silver migration effect into the metastable phase forms a micro-electric path, to enhance the relative dielectric permittivity of CaCu3Ti4O12 ceramics for electronic devices. Controlling the sintering time uniquely develops the metastable phase of as-sintered CaCu3Ti4O12 ceramics. A post-heating process that applies the migration of silver into the metastable phase increases the relative dielectric permittivity. At 1 kHz frequency, the relative dielectric permittivity at room temperature of the silver-migrated CaCu3Ti4O12 ceramics sintered for 2 h is 565.9 × 103, almost 52 times higher than that of the as-sintered CaCu3Ti4O12 ceramics. The selected area electron diffraction (SAED) patterns of the large and small grains were similar, but differed from those of the metastable region, including the grain boundary of the as-sintered CaCu3Ti4O12 ceramics sintered for 2 h by TEM technique. This phenomenon suggests that enabling Ag-migration into the metastable phase develops a micro-electric path that improves the relative dielectric permittivity of CaCu3Ti4O12 ceramics.

A Simplified Process of PMN-PZT Energy Harvester Based on Flammable Materials

With the increasing demand of auxiliary power unit in portable electronic devices, the concept of renewable energy harvesting near human surrounding environmental circumstance arouses an interest. As the field of microelectromechanical system (MEMS) has advanced, a clear need for the integration of materials other than silicon and its compounds into micromachined transducers has emerged. Piezoelectric materials are high energy density materials that scale very favorably upon miniaturization and that has led to an ever-growing interest in piezoelectric films for MEMS applications. However, conventional powder processing and machining cannot meet the requirement of such fine ceramic structure. Advanced technologies such as those using lasers and soft PDMS modeling method have been available for micro-patterning of ceramics but are not viable for large-scale production. It is difficult and time-consuming to pattern fine scale ceramics. In this paper, we fabricated simple process of MEMS based energy harvester by employing the flammable materials with PMN-PZT micro-pillar structure. The optimum aspect ratio of thickness/length for the ceramic pillar dielectric properties and micro-structure will be discussed.

Multi-layer Ceramic-Pillar Composite Structures for Piezoelectric Energy Harvesters

In this paper, we will discuss piezoelectric energy harvesters of multi-layered ceramic-pillar composite structures to be used as the energy source of small size electronic devices. 0.2(PbMg1/3Nb2/3O3)-0.8(PbZr0.475Ti0.525O3) ceramics and polydi-methylsiloxane (PDMS) were employed as piezoelectric ceramic-pillar composite, which prepared in forms of rectangular pillar structures. The piezoelectric ceramic-pillar composites were sintered separately and attached on the metallic bottom electrode with poled states. Symmetric upper electrodes were attached on the other side. Subsequently, the ceramic-pillar structures of composite material were manufactured with single-layer, double-layer and triple-layer devices. Both of multi-layer and single layer devices will be compared with several analysis methods. Piezoelectric properties will be discussed including the piezoelectric constant. Also, the output power of the multi-layer and single layer devices will be studied.

(1-x)(PbMgNbO3-PbZrTiO3)-x(BaTiO3) Piezoelectric Ceramics

The Pb(Mn1/3Nb2/3)O3-Pb(Ti,Zr)O3 system near the morphotropic phase boundary (MPB) can be expected to provide high piezoelectric constant and electromechanical coupling coefficient. Therefore it has used as an excellent candidate for piezoelectric applications including the high-power application. In this study, electric field-induced phase transition in PMN-PZT-based ceramics at a relatively low field of 40 kV/cm will be discussed. The structural and electrical properties of (1-x)(PMN-PZT)-xBT ceramics were investigated as a function of the BaTiO3 content (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5). Phase formation behavior was studied by an X-ray diffraction method. Room temperature SEM investigation revealed common trends in the grain structure with increasing BaTiO3 content.