Nd3+:CaLa2B10O19晶体的生长和性质研究

用泡生法生长出不同Nd3+掺杂浓度的Nd3+:CaLa2B10O19(NLCB)晶体,测试了晶体的透射光谱、荧光光谱、倍频效应等性质.NLCB晶体在580nm和805nm处有很强的吸收,能与二极管激光器有效耦合.在900nm和1.06μm处各有一荧光峰,1.06μm处的荧光寿命为75μs.NLCB的粉末倍频效应为KDP的2倍.     

Na5[B2P3O13]晶体双晶结构的研究

采用泡生法和b向籽晶生长出尺寸为22mm×24mm×20mm的透明Na5[B2P3O13]晶体.晶体定向中发现(100)和(001)晶面的一级衍射出现双峰;正交偏光显微镜下观察晶体的(010)切片,看到清晰的明暗条纹;当一束激光正入射(010)切片时,产生衍射现象;用同步辐射白光X射线形貌术拍摄了(100)、(010)和(001)切片的Laue像,观察到了晶体的孪晶结构,再借助(010)切片的化学腐蚀研究,推出该晶体为规则的聚片双晶,其结合面为(001).     

α-NiSO4·6H2O晶体生长与光学性质

用水溶液降温法生长出光学品级的α-NiSO4·6H2O大单晶,对晶体的透过光谱和(001)晶面的X射线衍射性能进行了测试和表征.     

高温相偏硼酸钡（α—BaB2O4）晶体的缺陷钎为分析

运用同步辐射X射线白光形貌研究了α-BaB2O4晶体内部的完整性,并分析了α-BaB2O4晶体的缺陷行为及缺陷形成原因。在（001）面发现生长扇界和亚晶界，而在（100）面和（120）面分别观察了位错，位错簇以及针状包裹体。使用双晶衍射实验发现在（001）面有生长条纹，这些生长条纹呈环形，该条纹与熔体中温度波动而导致的生长速度波动有关。运用白光形貌拍摄到高清晰的劳埃斑，表明晶体为三方结构。     

高温相偏硼酸钡(α-BaB2O4)晶体的缺陷行为分析

运用同步辐射X射线白光形貌研究了α-BaB2O4晶体内部的完整性,并分析了α-BaB2O4晶体的缺陷行为及缺陷形成原因.在(001)面发现生长扇界和亚晶界,而在(100)面和(120)面分别观察到了位错、位错簇以及针状包裹体.使用双晶衍射实验发现在(001)面有生长条纹,这些生长条纹呈环形,该条纹与熔体中温度波动而导致的生长速率波动有关.运用白光形貌拍摄到高清晰的劳埃斑,表明晶体为三方结构.     

K2Al2B2O7-NaF体系的热分析研究

用热分析的方法研究了KABO-NaF体系的物相关系,提出了KABO-NaF体系的赝二元相图.KABO和NaF可以形成低共熔体系,D KABO含量约30;时低共熔温度约为790℃.KABO在体系中的摩尔百分含量为30;～40;之间为KABO结晶区.KABO-NaF体系在500℃左右发生一个放热过程,675℃左右有一个复杂的吸热相变过程.     

Al-Fe3O4体系在机械力化学过程中的物理化学变化

将纳米磁性粒子嵌入到绝缘基体中形成的磁性复合粒子,在许多方面具有重要意义.本文利用Al-Fe3O4通过机械力化学方法原位生成Fe/Al2O3 磁性复合粒子.通过对球磨不同时间的Al-Fe3O4粉末进行X射线衍射(XRD)和示差扫描量热(DSC)分析,结果表明Al-Fe3O4混合粉末通过机械力化学方法可获得Fe/Al2O3复合粒子.同时较为详细地研究了上述体系在机械力化学过程中的物理化学变化,并提出了机械力化学过程中Al-Fe3O4体系固相反应的方式.     

CsLiB6O10晶体及熔体微结构的高温拉曼光谱研究

本文利用高温原位拉曼光谱技术,测定了非线性光学晶体硼酸铯锂(CsLiB6O10,CLBO)晶体及其熔体的变温拉曼光谱.利用密度泛函理论计算了基本单元为(B3O7)5-六元环的CLBO晶体的拉曼光谱,并对振动模式进行了分析归属.在升温过程中,CLBO晶体的拉曼光谱出现展宽和红移,无相变发生;在熔化过程中,CLBO晶体微结构中(B3O7)5-六元环的[BO4]四面体发生异构化反应,转变为[BO3]三角形,即晶体相中的(B3O7)5-环变为熔体中的(B3O6)3-环.利用量子化学从头计算方法计算分析了熔体中结构基元的拉曼光谱谱学特征,结合熔体实测结果,表明CLBO熔体的阴离子基元为四个(B3O6)3-六元环组成的大四元环超级结构.     

Li2B4O7晶体在SAW技术中的应用研究

采用CZ法生长了30×30mm3的Li2B4O7单晶体.对晶体的压电性能进行了研究,弹性系数的交叉分量少,数值相对较小;在(001)面内有较高的声波传播速度,其变化范围为6500～7080m/s,在[001]方向有较低的声波传播速度,大约为5160m/s;而压电性能表明在不同方向的机电耦合系数均比石英晶体相应参数大得多.对晶体谐振器和压控震荡器的性能进行了研究,发现其机电耦合系数近似石英的十倍,很适合用来制作宽频器件.晶体谐振器的频率温度特性为抛物线型,其转变温度在室温,在-10℃～55℃温度范围内频率变化为3×10-4,具有良好的频谱响应,其寄生频率高出主振180kHz,衰减大于30dB,完全能满足器件使用要求.晶体滤波器3dB带宽的相对宽为1;,而石英仅为0.4;.     

BaTiO3改性PZNT91/9晶体的生长工艺研究

采用底部冷却高温熔剂法(BCSG)成功地生长了BaTiO3改性PZNT91/9晶体,其中最大晶体(J3)尺寸达15 mm×13 mm,晶体呈浅黄色,箭头形.采用1～1.6 L/min的氧气流速能有效引发成核,而且通过康泰尓电阻丝实现点冷,可以有效控制成核数目.XRD分析表明:添加BaTiO3的晶体为纯钙钛矿相,晶体显露面为{001}面,说明添加BaTiO3能有效抑制焦绿石相,促进钙钛矿相的形成.     

赝二元系LiF-SrAlF5相图

本文通过差热分析(DTA)和X射线粉末衍射(XRD)方法研究了赝二元系LiF-SrAlF5的相平衡关系.该赝二元系在LiF:SrAlF5=1:1处形成一致融熔化合物LiSrAlF6,其熔点为765℃,并分别在LiF-LiFSrAlF6和LiSrAlF6-SrAlF5区域出现两个低共熔点,其共晶温度分别为673℃和705℃,根据体系的相图,采用坩埚下降法生长出氟化物激光晶体Cr3+:LiSrAlF6.     

Phase Diagram Study of Succinonitrile-Vanillin Organic Alloy System

Phase diagram studies of succinonitrile-vanillin system show the formation of 2:1 congruent melting type compound. Crystallization velocities of pure components, succinonitrile-vanillin complex, and two eutectics have been determined at different undercoolings. On the basis of heat of fusion measurements, excess thermodynamic functions have been calculated. Microstructural studies revealed that impurities modify the morphology. FTIR spectral studies and computer simulation have shown the existence of hydrogen bonding in the eutectics and the congruent melting compound. On the basis of experimental results, the mechanism of formation of eutectics and its solidification behavior are discussed.     

H3BO3添加对MgAl2O4-CaAl4O7-CaAl12O19复合陶瓷的相演变和力学性能的影响

用固相烧结工艺在1300～1600℃温度下制备了MgAl2O4-CaAl4O7-CaAl12O19(MA-CA2-CA6)耐高温复合陶瓷,研究了H3BO3添加对该陶瓷的主相含量、显微结构和力学性能的影响.结果 表明,H3BO3在MA-CA2-CA6复合材料中产生少量的富硼液相,加速了基体中物质互相扩散和转移,促使CA2相通过溶解沉淀机制生成了片状的CA6和硼酸钙液相,并使CA6晶粒由长板片状向短片等轴状演变,提高了材料的力学性能,有效促进了MA-CA2-CA6复合材料显微结构致密化.经1600℃下烧结的样品,当添加H3BO3含量为5wt;时,样品中CA2相含量由58.63;降为7;,而CA6相含量由31.22;增为75.2;,同时样品的显气孔率减少至9.7;,其体积密度增大到3.18 g/cm3,此时MA-CA2-CA6耐高温复合陶瓷显微结构致密,力学性能最佳.     

Elements of the Phase Diagram of YbInCu4

To clearify how the valence transition temperature of YbInCu₄ is connected with the composition of the grown crystals, we investigated the phase diagram. Since elements of the liquidus curve of the system Yb-In-Cu were already known we focused on the solidus curve in the surrounding of the valence changing YbInCu₄. Bridgman-technique for crystal growth was used. The composition of the solidified crystals was determined by means of wavelength-dispersive X-ray analysis. The valence transition temperature is measured via the lattice constant by low temperature X-ray diffraction. Results are, that the assumed exchange of Yb and In, which is indicated in the formula Yb_xIn_2-xCu₄ seems to be not correct. Not the quasi-binary section for constant Copper content should be used, but one for constant Ytterbium content. Starting compositions with an excess of Ytterbium lead to the substitution of Indium by Copper. The valence transition temperature of these crystals is shifted from 40K to 70K.     

The P-T-x Phase Diagram of the Mn-As System

The solid-liquid-vapour phase diagram of the Mn–As system has been determined in the range of 40–100 at% As. The melting point of equiatomic MnAs was found to be 936 ± 1°C at an arsenic pressure of 4 · 10⁻² atm.     

Elastic properties of the dithionates Na2S2O6 · 2 H2O,K2S2O6, Rb2S2O6, CaS2O6 · 4H2O and SrS2O6 · 4 H2O

Single crystals of the title compounds having optical quality and dimensions of several cm were grown from aqueous solutions. The elastic and thermoelastic constants were determined from ultrasonic resonance frequencies of thick plates. The true point symmetry of K₂S₂O₆ and Rb₂S₂O₆, which is screened by a hexagonal hypermorphy, could be clearly revealed to be trigonal (32) by the existence of the elastic constant c₁₄. In the case of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O the constant c₁₄ of the specimens appeared too small to confirm the trigonal symmetry group required from electrooptic and non-linear optic effects unambiguously. The isotypy of K₂S₂O₂ and Rb₂S₂O₆ as well as that of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O is confirmed by their elastic behaviour. The mean elastic stiffness of dithionates is closely related to that of the corresponding sulphates. In the vicinity of the second-order phase transition of K₂S₂O₆ near 235 K weak anomalies of the temperature derivatives of the longitudinal elastic stiffnesses are observed.     

Liquid Phase Epitaxy (LPE) of YB2Cu3O7-δ High Tc Superconductors

YBa₂Cu₃O_7-δ films were grown by liquid phase epitaxy in Y-ZrO₂ crucibles on (110)NdGaO₃ substrates. A change in the preferred crystallographic growth direction was observed reproducibly. The growth mode changes from pure c-axis oriented over mixed c/a-axis oriented films to pure a-axis oriented films with increasing undercooling. X-ray diffraction measurements and atomic force microscopy investigations with c-axis oriented as well as a-axis oriented films are presented. It will be shown that atomically smooth steps with 0.2-0.8 μM width can be achieved by LPE, which are free from melt remnants. Furthermore the values for the enthalpy of dissolution from literature, which are varying in a wide range, will be combined and a new value will be calculated in terms of a multi particle model.     

GO/Tb4 O7复合材料的光催化性能研究

以氧化石墨烯(GO)和氧化铽(Tb4 O7)为原材料,采用水热法制备了GO/Tb4 O7复合粉体.通过SEM、XRD和分光光度计等手段对复合材料粉体进行了分析.用罗丹明B溶液作为模拟污染物,在光催化反应仪中采用紫外光照射不同时间后,利用分光光度计测试其光催化性能.实验结果表明:复合材料粉体中,氧化铽颗粒基本可以均匀的分布在GO表面;随着GO含量(6;,8;,10;)的增加,复合材料粉体和罗丹明B的反应速率逐渐加快;在60 min时三种复合材料粉体的降解率分别为98.40;、98.64;、98.94;.     

Phase Diagram and Dielectric Studies in Hydrogen-Bonded Liquid Crystal System

The thermal and dielectric behaviors of mixtures were investigated for systems of p-n-hexyloxybenzoic acid (6OBA) and p-n-octyloxybenzoic acid (8OBA) by differential scanning calorimetry, polarized optical microscopy, and dielectric measurements. The T-X phase diagram was obtained for this system. Eutectic composition was calculated and received experimentally. Enthalpies of mixing were calculated to describe phase transitions physically. All mixtures show enantiotropic smectic and nematic phases. Dielectric permittivity has higher value for the mixture with fractional proportion of 30 to 70% mol for 8OBA than that for initial acid. It is assumed that co-crystallization of initial compound occurs when the ratio of components is close to equimolar ratio.