Korea Advanced Institute of Science and Technology

Ho Yong Lee

Sung Yoon Chung

Suk-Joong L Kang

Suk Joong Kang

Byung Kee Lee

Young Woo Rhee

Yang Il Jung

A method of manufacturing an alumina-based ceramic includes sintering a powder compact of an iron-containing alumina powder in an atmosphere (N , 95 N -5 H , H ) of a relatively low oxygen partial pressure, and annealing in an atmosphere (80 N -20 O , O ) higher in oxygen partial pressure than the sintering atmosphere to provide an alumina-based ceramic with a grain-boundary migration layer on a surface thereof. The resulting undulated grain boundaries on the surface layer suppress and deflect the crack propagation, thereby improving the short-crack toughness. The formation of a grain-boundary migration layer on the surface of an alumina-based ceramic brings about a great improvement in short-crack related properties, including durability and wear resistance.

Method for manufacturing surface-modified alumina-based ceramics

A method for making a BaTiO -based dielectric having a high dielectric constant and a low dielectric loss wherein, a BaTiO -based body is subjected to a pre-heat treatment in a hydrogen (H ) atmosphere or a reducing atmosphere containing mixed gas of hydrogen and nitrogen in a ratio of hydrogen:nitrogen&equals;5 to 100%:0 to 95% prior to a sintering process in the manufacture of dielectrics, in order to obtain a reduced average grain size of BaTiO . By virtue of the reducing average grain size of BaTiO , a BaTiO -based dielectric having a high dielectric constant and a low dielectric loss is obtained. This method provides an advantage in that it is possible to make a BaTiO -based dielectric having a very small average grain size while having a high relative density in accordance with a simple heat treatment conducted for pure BaTiO or even for BaTiO added with an additive in a reducing atmosphere at a temperature less than a liquid phase forming temperature, prior to a sintering process for sintering the BaTiO .

Method for making BaTiO3-based dielectric

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Choongchungnam-do, South Korea

Ho Yong Lee