高分辨X射线衍射术对NdP_5O_(14)晶体的自发应变及铁弹畴结构的研究

Investigation on the Spontaneous Strain and Ferroelastic Domain Structures in NdP_5O_(14) Crystals by High Resolution X-ray Diffractometry

利用助溶剂法 ,已经生长出 15mm× 2 5mm× 6 0mm的大尺寸NdP5O14 (NPP)晶体。用高分辨X射线衍射术对自发应变及铁弹畴结构进行了研究。对几个不同的反射 ,可在其摇摆曲线上观测到由基体畴和铁弹畴之间的取向差导致的反射峰的分离。通过反射峰分离的特点 ,可以确定铁弹畴结构。NPP晶体中大多数铁弹畴为a型畴 ,b型畴只出现在严重形变的区域。基于NdP5O14 晶体畴结构 ,我们分别计算了 80 2 ,40 2和 2 0 4反射的峰分离量。实验测量结果符合计算结果。另外 ,通过测量基体畴和铁弹畴的 80 0反射的峰分离量我们确定了NdP5O14 的自发应变是 0 .0 0 82。通过结构和对称性分析 ,我们对这种晶体的畴结构进行了详细讨论。

Large NdP 5O 14 crystal with dimension of 15mm×25mm×60mm has been grown by flux method.The spontaneous strains and ferroelastic domain structures have been investigated by high resolution X ray diffractometry.The reflection peak separations resulting from the misorientation between matrix domain and ferroelastic domain were observed in the rocking curves for several different reflections.Based on the features of the reflection peak separations,the ferroelastic domain structures were determined.It is found that most of the ferroelastic domains in NdP 5O 14 are of type a ,while type b ferroelastic domains only appear in the serious strain regions. Based on the domain structures of NdP 5O 14 ,the reflection peak separations for 802,402 and 204 reflections were calculated respectively.And the experimental observations are in agreement with the calculations very well.In addition,the spontaneous strain in NdP 5O 14 was determined to be 0.0082 by measuring the peak separation between two 800 diffraction from the matrix domain and the ferroelastic domain respectively.A detailed discussion on domain structures in this crystals is given in terms of structural and symmetry analyses.