摘要
利用X射线衍射(XRD)、扫描电镜(SEM)等手段,研究了在5 GPa压力下六方ZnO粉末的结晶过程。系统考查了温度与保温时间对ZnO扩散与结晶过程的影响。结果发现,在高压下ZnO固体的扩散速度大大增加,400℃保温0.5 h即可获得理论密度达99%以上的单相、致密的六方相ZnO陶瓷,所有样品均沿晶界开裂,并导致500℃以上只能获得单晶与多晶混合的粉末样品;850℃保温5 min可制备出平均尺寸超过100μm、最大尺寸超过350μm的浅黄色单晶。对实验结果的分析表明:ZnO固体在高压下可能存在一种超快极性扩散机制,这一效应使高压下的ZnO晶粒沿择优方向迅速生长,晶界快速迁移,相邻晶粒生长融合,最后形成单晶;而晶粒在生长过程中沿其它方向发生收缩,促使样品沿晶界开裂。
The effects of heating temperature and duration time on the process of ZnO crystallization under the pressure of 5 GPa are studied systemically by the methods of X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The experimental results show that the diffusion rate of ZnO increases greatly under high-pressure and the sample density higher than 99% of the theoretical value can be achieved after heated at 400 ℃ and 5 GPa for 0. 5 h. With the increasing of the heating temperature,micro-cracks develop along crystal boundary in all samples, and eventually ZnO powder mixed with single crystals and poly-crystals forms above 500 ℃. The pale yellow crystallites with an average size of 100 μm and the largest size more than 350 μm was obtained at 850 ℃ after heating of 5 rain. The sample morphology analysis shows that the reason for the ultra fast crystallization of ZnO under high-pressure is possibly caused by a very quick diffusion rate of ZnO along certain direction. The crystal boundary along such direction moves very quickly under high-pressure until the neighboring microcrystals merge into a single crystal in a short time, while the micro-crystals shrink in the other direction and cause micro-cracks along other crystal boundaries.
出处
《高压物理学报》
EI
CAS
CSCD
北大核心
2008年第1期85-88,共4页
Chinese Journal of High Pressure Physics
基金
江苏省青蓝工程资助项目
常州市工业攻关项目(CE2006095)
关键词
ZNO
高压
晶体生长
ZnO
high-pressure
crystal growth
