Some New Smectic F Materials

In the course of studies on the smectic C phase, we have succeeded in preparing three new compounds each of which exhibits a well defined smectic F phase. In all of these materials, the F phase gives a smectic C phase on heating and a smectic H phase on cooling. Moreover, these three compounds are members of two related homologous series of esters; therefore it seems probable that many more of the other homologues will exhibit smectic F properties.     

Smectic F Phases in the Terephthalyidene-Bis-4-n-Alkylanilines

Recently terephthalylidene-bis-4-n-pentyl-aniline (TBPA) was reported to have two types of tilted smectic B (smectic H) phase. However, our study of this material shows that this compound has a smectic F phase and a smectic H phase, and not two H phases as previously thought.     

CsSbSO4F2晶体的光学特性研究

通过溶液法合成了一种非中心结构长条状的CsSbSO₄F₂晶体.其晶体结构属于空间群Pna2₁,结构中[SbO₂F₂]与[SO₄]多面体共顶点连接形成了一维链状结构,Cs⁺填充在长链之间维持电荷平衡.利用Kurtz-Perry方法对晶体进行粉末倍频测试,表明CsSbSO₄F₂属于可相位匹配的物质,其倍频效应约为KH₂PO₄的0.65倍.紫外-可见光-近红外漫反射光谱显示,该物质的截止波长为233 nm.光学性能测试表明,CsSbSO₄F₂在紫外区域有潜在应用.     

Dielectric reorientation of smectic C,F and I phases

As shown for 4 liquid crystalline substances also smectic F and smectic I phases may be reoriented by an electric field similar to a smectic C phase. The threshold voltage of the effect was determined approximately. For one substance the tilt angle of the smectic C and I phase could be measured by means of the dielectric reorientation.     

C和F掺杂p型ZnO的第一性原理研究

采用基于密度泛函理论的第一性原理计算方法对C/F单掺杂ZnO和C-F共掺杂ZnO的O位体系进行了研究,讨论了掺杂体系的稳定性、电子结构和电学性质、光学性质.研究结果表明C和F共掺的形成能比C单掺的形成能小很多,即C和F共掺增加了体系的稳定性;计算获得的电导率之比分别为σC-ZnO/σZnO=9.45,σF-ZnO/σZnO=6.78,σC-F-ZnO/σZnO=19.62,显然,C和F共掺杂对ZnO体系的电导率增强效果最明显;载流子迁移率之比μC-ZnO/μZnO=1.67,μF-ZnO/μZnO =2.31,μC-F-ZnO/μZnO=2.50,说明C和F共掺增加了载流子迁移率.综合电导率和载流子迁移率二者结果,可认为C和F共掺极大地提高了ZnO的导电性.ZnO掺杂体系在可见光波长范围内透射率大于95;,具有良好的透光性.计算结果为实验上制备p型透明导电ZnO材料提供了理论指导.     

Structure and Correlations in Smectic B,F and I Phases

The question of which of the known smetic phases exhibitis long range 3 dimensional order is first discussed briefly, The major theme of the paper is the nature of the structure and correlations in S_B, S_F, and S₁ phases. Results are presented about the temperture dependence of the interlayer stacking arrangement and the existence of strong layer undulations in crystalline S_B phases and about the existence of a S_B phase with very weak positional correlations between layers and short range order within the layers.

The raltion between the S₁ and S_F structures is established for the first time: both consist of uncorrelated layers in which the molecules are tilted relative to the layer normal and have limited positional correlations within layers. Both have 3-d long range bond orientational order of the C-centered monoclinic lattices. They differ in the direction of tilt of the molecules relative to the pseudo-hexagonal packing in the plane normal to the long axes: in S_F the tilet is directed towards an edge of the hexagon, while in S₁ it is directed towards an apex. These results enable previously described phases to be classified (or reclassified) as S₁ phases and emphasise the existence of more ordered phases with similar tilt to the S₁ phase but otherwise analagous to S_G and S_H—we call these S_G and S_H. Finally a preliminary repor is given of X-ray structural work which shows that the recently postulated S₁ and S_K phases do not exist.     

Electrical conductivity of antimony oxofluoride Sb3O2F5

The conductivity of antimony oxofluoride Sb₃O₂F₅ is investigated by the complex impedance method in the temperature range of 400–505 K. Sb₃O₂F₅ powder has been prepared by solid-phase synthesis in nickel ampoules at 473 K for 5 h in an argon atmosphere. The Sb₃O₂F₅ conductivity has an ionic character. The ionic conductivity is found to be 5 × 10^?5 S/cm (at 505 K), with an ion-carrier migration energy of 0.82 eV.     

循环流化床粉煤灰可控制备高纯F型八面沸石研究

利用粉煤灰制备沸石分子筛是其高值化利用的重要方向之一.以循环流化床粉煤灰为原料,采用酸浸预处理-氢氧化钠碱熔活化-水热晶化法制备F型八面沸石,并用于吸附亚甲基蓝.考察酸浸温度、碱熔温度及碱灰质量比对粉煤灰结构的影响及碱熔温度、碱灰质量比、液固比及晶化时间对沸石的结构和形貌的影响.通过XRD和SEM对粉煤灰沸石的晶体结构和形貌进行表征.结果表明,利用循环流化床粉煤灰制备高纯F型八面沸石适宜条件为碱熔温度550℃,碱灰质量比1.5:1,液固比12 mL/g,晶体导向剂用量10;,晶化温度100℃,晶化时间20 h.其比表面积高达357 m2/g,且对亚甲基蓝的饱和吸附量高达178 mg/g.     

温度梯度法BaY2F8晶体生长中的小面研究

采用温度梯度法生长了BaY2F8晶体,通过X射线定向仪确定晶体自发沿[001]方向生长.通过对不同截面的显微观察和分析,研究认为生长方向与竖直方向不平行是诱发(100)、(130)、(130)等小面生长的重要因素.由于温度的波动和径向温度梯度的存在,会造成晶体生长过程中的组分过冷,引发晶面上出现胞状凸起,影响了晶体的生长质量.     

Crystal structure of (NH4)5Sc3F14

The equilibrium in the (NH₄)₃ScF₆-NH₄HF₂-H₂O system in the range of hydrodifluoride ammonium solution concentrations of 0.05–3.5 mol/L at temperatures of 18 and 90°C is studied. The composition of solid phases in equilibrium is analyzed using elemental analysis, X-ray diffraction, and neutron diffraction. A new phase, (NH₄)₅Sc₃F₁₄ with a tetragonal lattice (sp. gr. I4₁/a, unit-cell parameters a = 0.80843 nm and c = 2.5177 nm), is found at fluoride ion concentrations in the solution of ≤1.06 mol/L at 18°C and 2.92–3.01 mol/L at 90°C; the crystal structure of this phase is determined.     

Fluorine-Ionic Conductivity of Superionic Conductor Crystals Na0.37Tb0.63F2.26

Crystallography Reports - The temperature dependence (in the range of 479–827 K) of the fluorine-ionic conductivity of nonstoichiometric Na0.37Tb0.63F2.26 crystals with fluorite-type...     

Optical Properties of some TMTS(T)F2X Compounds

The infrared and visible reflectance of TMTSF₂PF₆ is reported. Data are given at high and low temperatures in the metallic range and for polarizations along and perpendicular to the highly conducting direction. Among the interesting features are a pseudogap in the far infrared conductivity along the highly conducting direction, and a mid-infrared plasma edge in the perpendicular direction. Unusual temperature dependent, near infrared absorptions may have implications for the band structure. For comparison some data on TMTSF₂AsF₆, TMTSF₂ClO₄, TMTSF₂ReO₄ and TMTTF₂PF₆ are presented.     

KBe2BO3F2的水热相变研究

研究了多种不同矿化剂对KBBF高温高压超临界水热条件下的相变的影响.归纳出KBe2 BO3 F2晶体“非整比溶解-非整比生长”的生长机制.通过这一机制对KBBF的结构多相性和非线性光学转换效率较低的问题有了新的认识.