[6a-A502-1~14] 9.1 Dielectrics, ferroelectrics

[6a-A502-6] Improvement in Dielectric Properties of Conductor/Insulator Composite Ceramic Capacitors by Microstructural Control

〇Shintaro Ueno¹, Yuya Hattori¹, Ichiro Fujii¹, Satoshi Wada¹ (1.Univ. of Yamanashi)

Keywords:Dielectrics, Composites, Low-temperature process

To develop ultrahigh-capacitance capacitors, we have focused on boundary layer (BL) capacitors which can exhibit a high dielectric constant over 10⁴. BL capacitors commonly consist of semiconductor grains and insulated grain boundaries with a thickness of a few nanometers. We tried to replace semiconductor layers with conductor layers such as metals and conductive oxides and develop conductor/insulator composite capacitors with BL structures. To avoid oxidization of metal layers or formation of solid solution between conductive-oxide and insulators, we proposed the low-temperature processes including solvothermal method for preparation of conductor/insulator composite capacitors. The microstructures of the BL capacitors can be seen as the assembly of conductor-insulator core-shell components. That means the BL capacitors can be fabricated by the conductor-insulator core-shell particles. For the case of metal/insulator perovskite oxide composites, The titanium metal/barium titanate (Ti/BT) composites consisting of Ti metal grains and BT boundary nanolayers were successfully prepared from the pressed Ti-BT core-shell particle compacts with various thicknesses of the BT shell layers by the hydrothermal method below 230 °C. The thickness of insulator shell layers and the resultant insulator boundary nanolayers can be precisely controlled by solvothermal conditions, and the effective dielectric constant increases up to over 10⁴ with a decrease in the thickness of insulated boundary nanolayers for Ti/BT composite capacitors. We have been also trying to fabricate the lanthanum nickelate (LN)/insulator composite with the BL structures.