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化学计量比LiNbO3晶体的畴结构及完整性研究 总被引:2,自引:2,他引:0
本文对用助熔剂提拉法生长的两种化学计量比LiNbO3晶体进行了测试分析,并与同成分LiNbO3晶体相比较.通过差热分析和X射线粉末衍射测试,得出随着晶体中Li2O含量的增加,其居里温度变高,晶格常数变小.用酸腐蚀晶体,通过直接观察和金相照片,分析其畴结构,得出SLN11是单畴生长,首次观察出SLN19晶体在Z切面上出现了三块面积较大的对称反畴区,将其称为区域性单畴.另外,还对晶体在(001)方向抛光面的不同位置测量了其回摆曲线,得到了其中SLN19晶体有着较完整的结晶面.期望通过改变生长参数,长出完全单畴且更加接近化学计量比的LiNbO3晶体. 相似文献
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利用助溶剂法,已经生长出15mm×25mm×60mm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802,402和204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800反射的峰分离量我们确定了NdP5O14的自发应变是0.0082.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. 相似文献
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CMTD晶体的螺位错生长机理 总被引:1,自引:0,他引:1
用原子力显微镜在有机非线性光学晶体CdHg(SCN)4(H6C2OS)2(CMTD)的(001)面上观察到了许多奇特的心形螺旋生长丘,这种心形线不同于由反向双螺位错发展而成的瑞德环(Frank-Read).我们认为这种心形螺旋生长丘的相邻层交替生长除了与21螺旋轴有关外,还与在台阶源附近形成的结构畴有关.在由心形缺口推展出去的直线"划痕"两侧的台阶流上观察到的相互垂直分布的二维核,使我们认为直线"划痕"可能是90°的结构畴.实验结果说明晶体的结构及台阶源附近的分子键合方向及强度使不同晶体的生长具有独特的规律性. 相似文献
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本文回顾了(Nd3+,Yb3+):Ca3(VO4)2晶体的研究历程,通过对晶体结构和对晶体激光性能研究年代的对比,认为高的泵浦阈值是由于晶体中存在的对泵浦光和激光散射很强的畴壁结构未被发现而造成的.讨论了极化的原理、建立了极化装置,采用Laue定向法和X射线定向仪定向法结合解决了(Nd3+,Yb3+):Ca3(VO4)2这种大晶格常数(c=3.8029nm)晶体的定向问题.把晶体的抛光面放入0.5mol;的温度为30℃的硼酸中腐蚀样品1h,用显微镜可以观察到畴结构.在~1100℃和电流密度为~10μA/mm2的条件下极化2h即可完成极化.变黑的极化样品可以通过把晶体放入马福炉中升温至850℃,保持1h,然后降至室温即可消除. 相似文献
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Yuma Tsuboi Hiromitsu KimuraHaruhiko Koizumi Satoshi Uda 《Journal of Crystal Growth》2009,311(16):4089-4093
The mechanism of polarization due to thermoelectric power and current-induced electric fields during the growth of LiNbO3 crystals was studied using a micro-pulling-down method. With no applied electric current, a +c single-domain crystal was grown regardless of the domain orientation of the seed crystal. This +c domain growth was consistent with the direction of the electric field caused by the thermoelectric power in the liquid, despite an opposing electric field in the solid due to the opposite sign of the Seebeck coefficient. Thus, it was the electric field in the liquid that determined the domain structure of the growing crystal. On the other hand, when a current was applied from the melt to the crystal, a −c domain crystal was grown. The electric current required for this domain inversion to occur became larger as the temperature gradient in the solid phase decreased. This shows that the electric field in the solid phase became large enough to induce domain inversion from +c to −c through a combination of the thermoelectric power in the solid phase and current-induced electric field. 相似文献
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MOCVD法制备一维定向ZnO晶须阵列及掺杂研究 总被引:5,自引:0,他引:5
采用大气开放式MOCVD技术,以Zn(C5H7O2)2为前驱物,在玻璃和单晶硅基片上生长了沿c轴高度定向、规则排布的氧化锌晶须阵列.在此基础上,采用多气路输送不同金属有机源的方法,进行了ZnO晶须的掺杂,制备了掺铝元素的一维定向晶须阵列.XRD结果表明未掺杂ZnO晶须为六方纤锌矿结构,沿c轴高度取向;掺铝ZnO晶须晶体结构仍为六方纤锌矿结构,沿c轴择优取向.SEM结果显示,未掺杂的ZnO晶须阵列排布规则,长径比达到20;掺杂ZnO晶须随着铝掺杂浓度的增加,晶须的形貌及排布规则性变差. 相似文献
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Hong Xu Yijian Jiang Xiujun Fan Yue Wang Guoqing Liu 《Crystal Research and Technology》2012,47(8):903-908
Large Ta2O5 single crystal with high‐dielectric permittivity was successfully grown by floating zone (FZ) method under air atmosphere. The grown crystal that has been obtained was typically about 8 mm in diameter and 90 mm in length. The crystal growth parameters were optimized. The crystal symmetry, characterized by means of X‐ray diffraction (XRD), was found to be tetragonal. The relative permittivity and loss tangent along growth and [001] direction were measured in the temperature range between ‐200 °C and 200 °C, which showed a strong dielectric anisotropy. At a frequency of 1 MHz and 20 °C, the dielectric permittivity along the growth direction and [001] direction are 81.17 and 25.04 respectively. The stabilization of high‐temperature phase can explain the dielectric enhancement. 相似文献
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运用X射线衍射(XRD)和X射线光电子能谱(XPS)对垂直布里奇曼法生长的ZnGeP2晶体的轴向组成进行分析,发现晶体的成分不均匀。采用Rietveld全谱拟合精修定量分析各物相的相对含量,发现晶体轴向组成分布存在较大差异。晶体肩部和尾部含有Ge和Zn3P2杂相,而主体部分为单相ZnGeP2、质量相对较高。傅里叶变换红外光谱(FTIR)的测试结果表明,晶体轴向成分的差异对其红外透过率有较大影响。经过适当的热处理工艺,可以提高晶体的均匀性,改善其光学性能。 相似文献
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Gang Yang Guojian Wang Wenchang Xiang Yutong Guan Yongchen Sun Dongming Mei Bruce Gray Yuen-Dat Chan 《Journal of Crystal Growth》2012,352(1):43-46
To grow high purity germanium (HPGe) crystals in an underground environment for ultra-low background experiments is being studied. In the present work, HPGe crystals along 〈100〉 direction have been grown by the Czochralski method. In order to investigate the distribution of the impurities as a function of length for a grown crystal, i.e. the axial direction, we fabricated a system to measure the resistivity along the axial direction at both room temperature and liquid nitrogen temperature. The distribution of the impurities along the radial direction was measured with a Hall Effect System. The results show that the carrier concentration in some crystals grown in a hydrogen atmosphere has an impurity level of about 1010/cm3, which meets the requirements of detector-grade crystals. 相似文献
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Y. L. Geng D. Xu D. L. Sun G. H. Zhang W. Du H. Y. Liu X. Q. Wang 《Crystal Research and Technology》2004,39(8):712-717
Morphology of the {100} faces of L‐arginine phosphate monohydrate (LAP) single crystal grown at 25 °C at a supersaturation of 0.32 has been discussed. The rectangular dislocation growth hillocks elongate along the b direction, which manifests the fast growth due to the strong Period Bond Chain (PBC) bonds along this direction. Apart from that, the growth hillocks are consistent with the macro‐morphology of the crystal grown at the pH value of about 4.2. The lopsided shapes of the hillocks result from step bunching. Triangular pits are assumed to form during the process of the steps getting across the impurities. The hollow cavities existing on the growth hillocks also elongate along the b direction and they can lead to the formation of other defects such as dislocations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献