Strong Anisotropy of KTiOPO4 Crystals under an Electric Field Observed by Synchrotron Radiation Topography

In-situ white-beam synchrotron radiation topographic observations under an electric field have been made on KTiOPO4 family crystals.The investigation shows a strong enhancement of diffracted intensity of hkl reflections(l≠0) and the topographic extinction contrast,when the field is applied along the polar axis.Doped and undoped samples with grown-in defects are studied in detail.It is believed that the movement of K^ ions driven by the field leads to a local accumulation of charges and the lattice distortion.All the field-related phenomena appear to be related to the one-dimensional ionic conductance.     

晶粒尺寸对锐钛矿TiO2相变压力的影响

采用在位高压Raman光谱和高压同步辐射能散X射线衍射技术,在室温下对晶粒尺寸为10nm的锐钛矿TiO2进行了压致相变研究,压力范围分别为42．9GPa和23．0GPa,实验结果表明,在16．3GPa TiO2发生了一次结构相变,由原来的锐钛矿结构变为α－PbO2结构（TiO2-Ⅱ）,该相变是不可逆的。同体材料TiO2的高压相变结果比较,由于晶粒尺寸的效应,纳米尺寸的锐钛矿TiO2的相变压力明显高于体材料的相变压力。