The crystal structure of Ca( Mg1/3Ta2/3) O3 ceramics with complex perovskite structure was investigated by using the newest precession electron diffraction ( PED) technique. Under certain precession angle, PED can eliminate the dynamic effects during electron diffraction. The B site cation ordering was found to dominate the crystal structure. The symmetry elements could be directly detected in the PED pattern Referring to the process that used by CBED( Convergent beam electron diffraction) to detect point group of crystal, Ca( Mg1/3Ta2/3 )O3 ceramics was determined to be with 2/m point group according to the PED pattern.%采用最新的旋进电子衍射技术研究了Ca(Mg1/3Ta2/3)O3复合钙钛矿陶瓷的晶体结构.在一定的旋进角下,旋进电子衍射可以很好地消除传统电子衍射中的动力学效应,揭示了Ca(Mg1/3Ta2/3)O3结构中B位离子有序是决定其晶体结构的关键因素,而通过旋进电子衍射花样中对称元素的直观确认,并结合会聚束晶体点群确认方法,证实了Ca(Mg1/3Ta2/3)O3陶瓷属于单斜2/m点群.
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