Kim, Chang-Hoon
(LCR Material Development Group, Samsung Electro-Mechanics)
,
Park, Kum-Jin
(LCR Material Development Group, Samsung Electro-Mechanics)
,
Yoon, Yeo-Joo
(Analytical Research Group, Samsung Electro-Mechanics)
,
Kim, Young-Tae
(LCR Material Development Group, Samsung Electro-Mechanics)
,
Hur, Kang-Heon
(LCR Development Team, Samsung Electro-Mechanics)
To understand the formation of core-shell structure in $BaTiO_3$ (BT) grains in multilayer ceramic capacitors, specimens were prepared with BT powders mixed with Y and Mg, and their microstructures were investigated with scanning electron microscopy, x-ray diffractometry, and transmission...
To understand the formation of core-shell structure in $BaTiO_3$ (BT) grains in multilayer ceramic capacitors, specimens were prepared with BT powders mixed with Y and Mg, and their microstructures were investigated with scanning electron microscopy, x-ray diffractometry, and transmission electron microscopy. Microstructural investigation showed that Y dissolved easily in BT lattice to a certain depth inside of the grain, whereas Mg tended to stay at grain boundaries rather than become incorporated into BT. It was considered that in case of Y and Mg addition in a proper ratio, Y could play a dominant role in the formation of shell leading to a slight dissolution of Mg in the shell. Next, the effects of ball-milling conditions on the core-shell formation were studied. As the ball-milling time increased, the milled powders did not show a significant change in size distribution but rather an increase of residual strain, which was attributed to the milling damage. The increase in milling damage facilitated the shell formation, leading to the increased shell portion in the core-shell grain.
To understand the formation of core-shell structure in $BaTiO_3$ (BT) grains in multilayer ceramic capacitors, specimens were prepared with BT powders mixed with Y and Mg, and their microstructures were investigated with scanning electron microscopy, x-ray diffractometry, and transmission electron microscopy. Microstructural investigation showed that Y dissolved easily in BT lattice to a certain depth inside of the grain, whereas Mg tended to stay at grain boundaries rather than become incorporated into BT. It was considered that in case of Y and Mg addition in a proper ratio, Y could play a dominant role in the formation of shell leading to a slight dissolution of Mg in the shell. Next, the effects of ball-milling conditions on the core-shell formation were studied. As the ball-milling time increased, the milled powders did not show a significant change in size distribution but rather an increase of residual strain, which was attributed to the milling damage. The increase in milling damage facilitated the shell formation, leading to the increased shell portion in the core-shell grain.
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대상 데이터
The starting powders were hydrothermally synthesized BaTiO3 (Sakai), MgCO3 (Kyorix), Y2O3 (Rhodia), BaCO3 (Sakai) and SiO2 (Kojundo Chemical). Aimed at understanding the contribution of additive elements to shell formation, we set the composition of specimens as shown in Table 1.
The disks were baked at 400oC for binder removal and annealed at 700oC for 1h in order to make them mechanically robust during the following processes. The specimens were sintered at 1350oC for 2h in N2-H2-H2O atmosphere.
이론/모형
Bulk density of sintered specimen was measured using Archimedes method. The disks were polished down to 0.
성능/효과
251 for 48 h. From the results of SEM, BET, and XRD of the powders, it is considered that the increase of ball-milling time from 12 h to 48 h did not induce any considerable change in the powder size distribution but resulted in increased milling damage in the powders, which would influence the microstructure of the sintered specimen.
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