Flash sintering produces eutectic microstructures in Al 2 O 3 –LaPO 4 versus conventional microstructures in 8YSZ–LaPO 4
Flash sintering produces eutectic microstructures in Al 2 O 3 –LaPO 4 versus conventional microstructures in 8YSZ–LaPO 4
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DOI：
10.1111/jace.17786
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发表时间：
2021-03
影响因子：
3.9
通讯作者：
Yingjie Yang;D. Mumm;M. Mecartney
中科院分区：
文献类型：
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作者：
Yingjie Yang;D. Mumm;M. Mecartney
独居石（LaPO 4）即使在1130 V/cm的高电场和1450°C的温度下也不会闪速烧结，而8 YSZ-LaPO 4和Al 2 O3-LaPO 4的复合系统已被发现更容易闪速烧结。添加到LaPO 4中的8 YSZ使用仅250 V/cm的电场将用于闪速的熔炉温度大大降低到1100°C。在这些实验中，单独的-Al 2 O3即使在1130 V/cm的高电场下也不会在1450°C下闪速烧结，但是Al 2 O3-LaPO 4粉末的复合材料在1450°C下在900 - 1080 V/cm下闪速烧结。在2 ~ 25 mA/mm 2的电流限制下，对Al 2 O3-LaPO 4复合材料进行了快速烧结。通过扫描电子显微镜（SEM）和透射电子显微镜（TEM）评估微观结构。观察到在所有闪速烧结的Al 2 O3-LaPO 4复合材料中形成共晶组织。在较高的功率（较高的电流极限）下，发现具有规则层状区域的共晶结构与具有大的六边形-Al 2 O3晶粒（高达75 μ m）和大的不规则LaPO 4晶粒的通道区域（电流和温度都最高的区域）共存。在较低的功率（较低的电流极限）下，不规则的共晶微观结构占主导地位，并且存在最小的异常晶粒生长。这些结果表明，Al 2 O3-LaPO 4是一个共晶形成系统和共晶温度达到局部闪速烧结过程中的区域。这些具有100 nm尺度的层状尺寸的共晶微结构提供了改善机械性能的潜力。
While monazite (LaPO4) does not flash sinter even at high fields of 1130 V/cm and temperatures of 1450°C, composite systems of 8YSZ–LaPO4and Al2O3–LaPO4have been found to more readily flash sinter. 8YSZ added to LaPO4greatly lowered the furnace temperature for flash to 1100°C using a field of only 250 V/cm. In these experiments, ‐Al2O3alone also did not flash sinter at 1450°C even with high fields of 1130 V/cm, but composites of Al2O3–LaPO4powders flash sintered at 900‐1080 V/cm at 1450°C. Alumina–monazite (Al2O3–LaPO4) composites with compositions ranging from 25 vol% to 75 vol% Al2O3were flash sintered with current limits from 2 to 25 mA/mm2. Microstructures were evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A eutectic microstructure was observed to form in all flash sintered Al2O3–LaPO4composites. With higher power (higher current limits), eutectic structures with regular lamellar regions were found to coexist in the channeled region (where both the current and the temperature were the highest) with large hexagonal‐shaped ‐Al2O3grains (up to 75 m) and large irregular LaPO4grains. With lower power (lower current limits), an irregular eutectic microstructure was dominant, and there was minimal abnormal grain growth. These results indicate that Al2O3–LaPO4is a eutectic‐forming system and the eutectic temperature was reached locally during flash sintering in regions. These eutectic microstructures with lamellar dimensions on the scale of 100 nm offer potential for improved mechanical properties.