Effect of step free energy on delayed abnormal grain growth in a liquid phase-sintered BaTiO3 model system

2011 ◽  
Vol 31 (5) ◽  
pp. 755-762 ◽  
Author(s):  
Yoon Ho Heo ◽  
Sang-Chae Jeon ◽  
John G. Fisher ◽  
Si-Young Choi ◽  
Kang-Heon Hur ◽  
...  
Keyword(s):  
Free Energy ◽  
Liquid Phase ◽  
Grain Growth ◽  
Model System ◽  
Abnormal Grain Growth

scholarly journals Low-Temperature Sintering of Apatite-Type Lanthanum Silicate with Fluoride Additives

2010 ◽  
Vol 62 ◽  
pp. 235-240
Author(s):  
Junichi Takahashi ◽  
Hidetoshi Honda ◽  
Takaya Akashi ◽  
Kazutomo Abe ◽  
Hidenobu Itoh ◽  
...  
Keyword(s):  
Activation Energy ◽  
Liquid Phase ◽  
Low Temperature ◽  
Bulk Density ◽  
Grain Growth ◽  
Low Temperatures ◽  
Abnormal Grain Growth ◽  
Low Temperature Sintering ◽  
Lanthanum Silicate ◽  
Apatite Type

Various fluorides (3 - 8 wt%) were added to a La9.33Si6O26 (LSO) powder synthesized by calcining the corresponding oxides mixture at 1100°C for 4 h. The addition of BaF2, AlF3 or Ba3Al2F12 caused an appreciable and substantial increase in bulk density after sintering at 1400º and 1450°C, respectively. These fluorides melt below 1400°C to form liquid phase which could assist the densification at low temperatures. Abnormal grain growth was observed for LSO samples with the addition of AlF3 and Ba3Al2F12, but it was effectively suppressed by stepwise sintering at 1400º and 1450°C. The BaF2 addition brought about the simultaneous promotion of densification and moderate grain growth, leading to the production of a densified LSO sample showing a conductivity of 1.5 x 10–2 Scm–1 at 800°C with an activation energy of 1.23 eV.

Effect of Grain Orientation on the Abnormal Grain Growth with Magetoplumbite Crystal Structure

2007 ◽  
Vol 558-559 ◽  
pp. 1265-1270 ◽  
Author(s):  
Sang Yeup Park ◽  
Jun Ho Song ◽  
Young Jin Cho
Keyword(s):  
Crystal Structure ◽  
Liquid Phase ◽  
Grain Growth ◽  
Grain Orientation ◽  
Grain Shape ◽  
Nucleation And Growth ◽  
Growth Behavior ◽  
Abnormal Grain Growth ◽  
Particle Orientation ◽  
Anisotropic Crystal

The nucleation and growth behavior of magentoplombite has been observed during the abnormal grain growth in the presence of liquid phase. Abnormal grain growth was explained in terms of grain orientation due to liquid phase. It has been observed that the nuclei formation for abnormal grain growth was driven by the capillary force due to the liquid phase. Because magnetoplumbite crystal structure has an anisotropic crystal nature, abnormal grain growth with faceted grain shape was observed depending on its chemical composition. The formation of nuclei and particle orientation was important for the occurrence of abnormal grain growth.

Step Free Energy Change and Microstructural Development in BaTiO3-SiO2

2007 ◽  
Vol 352 ◽  
pp. 25-30 ◽  
Author(s):  
Jaem Yung Chang ◽  
Suk Joong L. Kang
Keyword(s):  
Free Energy ◽  
Grain Growth ◽  
Driving Force ◽  
Growth Behavior ◽  
Abnormal Grain Growth ◽  
Free Energy Change ◽  
Energy Change ◽  
Microstructural Development ◽  
Two Phase ◽  
Grain Growth Behavior

The effect of step free energy on the grain growth behavior in a liquid matrix is studied in a model system BaTiO3-SiO2. BaTiO3-10SiO2 (mole %) powder compacts were sintered at 1280°C under various oxygen partial pressures (PO2), 0.2, ~ 10-17 and ~ 10-24 atm. As the step free energy decreases with the reduction of PO2, it was possible to observe the change in growth behavior with the reduction of the step free energy. At PO2 = 0.2 atm, essentially no grain growth (stagnant grain growth) occurred during sintering up to 50 h. At PO2 ≈ 10-17 atm, abnormal grain growth followed stagnant grain growth during extended sintering (incubation of abnormal grain growth). At PO2 ≈ 10-24 atm, normal grain growth occurred. These changes in growth behavior with PO2 and the step free energy reduction are explained in terms of the change in the critical driving force for appreciable growth relative to the maximum driving force for grain growth. The present experimental results provide an example of microstructure control in solid-liquid two- phase systems via step free energy change.

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