Yulian Tian

Growth, defects, and properties of GdCa4O(BO3)3 and Nd:GdCa4O(BO3)3 crystals

Pure and neodymium-doped gadolinium calcium oxoborate crystals of high quality were grown by the Czochralski method. The orientation of crystal was precisely determined, and the samples for measurements were prepared. Through synchrotron x-ray topography and high-resolution x-ray diffractometry, the twin structure was discovered. Some properties such as the figure of merit value, and dielectric, piezoelectric, and elastic constants were measured along with a discussion of the anisotropy of the laser properties.

Development of bulk SiC single crystal grown by physical vapor transport method

This paper reviews the development of bulk SiC single crystals grown by physical vapor transport method, including the polytype control, defects and doped consideration. In addition, defects in commercial 6H-SiC wafer, such as micropipes, hexagonal voids and subgrain boundaries, are examined by transmission optical microscopy, X-ray synchrotron topography in back-reflection geometry and high-resolution X-ray diffraction methods.

Characterization of Growth Defects in Nd:YCa4O(BO3)3 Crystals by Transmission Synchrotron Topography

The growth defects in Nd: YCa 4 O(BO 3 ) 3 (Nd: YCOB) crystals were investigated by transmission synchrotron topography. It was found that growth striations were the primary defects in Nd:YCOB crystals. Grown-in dislocations, mosaic blocks and inclusions were also observed in the crystals. The effect of temperature field on the formation of growth defects in the crystals was discussed.

Observation of inhomogeneity in congruent LiTaO3 crystal

Abstract The inhomogeneity in a congruent LiTaO 3 crystal has been observed by transmission synchrotron topography. Many extraordinary regions exist in congruent LiTaO 3 crystal and they often show diffraction intensity different from that of ordinary regions in synchrotron topographs. Differential thermal analysis indicates that the Curie temperature of the extraordinary region is lower than that of ordinary region, and the extraordinary region is really a high defect density region. The diffraction contrast of the extraordinary region in synchrotron topographs is explained qualitatively by a calculation at the selected wavelength.

Growth and defects in YbxY1−xAl3(BO3)4 crystals

YbxY1-xAl3(BO3)(4) (x = 0.1, 0.07 and 0) crystals have been grown by the flux method. The growth defects of YbxY1-xAl3(BO3)(4) crystals were detected by X-ray topography. It is found that the perfection of YbYAB crystal with low Yb dopant is better than that with high Yb dopant. In Yb0.1Y0.9Al3(BO3)(4) crystal, growth bands, growth boundaries, grown-in dislocations and inclusions were observed. However, the densities of growth defects for Yb0.07Y0.93Al3(BO3)(4) and YAl3(BO3)(4) are low and no obvious inclusions are observed in these crystals. In addition, growth twins were detected in YbxY1-xAl3(BO3)(4) crystal by using the chemical etching method. It is found that the growth twins occur frequently in Yb0.1Y0.9Al3(BO3)(4) crystal whereas no growth twin appears in YAl3(BO3)(4) crystal. Based on the experimental observations, the formation mechanism of growth twins is discussed. In the meantime, the effective measures for reducing the growth twins and defects are proposed

Image shifts resulting from the misorientation of two individuals in GdCa4O(BO3)(3) crystal

Large GdCa4O(BO3)(3) crystal has been grown by the Czochralski method. The quality of GdCa4O(BO3)(3) crystal was assessed by white-beam synchrotron radiation topography. It has been found that there is a sub-grain boundary in the GdCa4O(BO3)(3) crystal. The boundary divides the large GdCa4O(BO3)(3) crystal into two individuals. Due to the misorientation between the two individuals, the image shifts can be observed in the synchrotron topographs. Based on the misorientation determined by high resolution X-ray diffractometer, the image shifts were calculated for several reflections. The calculations are in agreement with the measurements from the topographs very well. In addition, the formation mechanism of sub-grain boundary is discussed

Growth defects in flux grown RbTiOAsO4 crystals observed with white-beam synchrotron radiation topography

Abstract The growth defects in flux grown RbTiOAsO 4 crystal have been investigated by white-beam synchrotron radiation topography. It is found that growth sector boundaries are the primary growth defects and they show strong X-ray kinematical contrast in the topograph. All the dislocations are growth induced and appear only in the near capping region. The area away from the capping region is nearly dislocation free. Growth bands show weak contrast in the X-ray topograph, which implies that the impurity contents are relatively low in various growth sectors and each growth sector is uniform in composition.

Comparative Study of KTiOPO4 crystals

High purity KTiOPO 4 (KTP) crystals have been grown using a flux method. The quality, SHG efficiency and damage threshold of KTP crystals grown from high purity reagents were compared with those grown from commercial reagents. Experimental results indicate that KTP crystals using a high purity charge contain less impurities and possess higher SHG efficiency and damage threshold than do crystals grown from commercial reagents. It is proposed that decreasing the concentrations of impurities is an effective way of raising the damage threshold for KTP crystals.