一种新型的固溶体——Mgx/2Li1-xIO3晶体结构随成分的变化

本文用室温、高温X射线衍射和差热分析等方法,研究了Mg_x/2Li_1-xIO₃晶体结构及其随成份和温度的变化。Mg(IO₃)₂·LiIO₃二元系形成一种新型的连续固溶体。在室温对于富LiIO₃的固溶体,晶体点阵沿x-y,平面产生畸变,其畸变开始随Mg(IO₃)₂含量的增加而加大,晶体的空间群从P6_{3关键词：}     

Al-Ti-V-M四元系合金TiAl3-VAl3-MAl3(M=Ni,Fe)赝三元系相图的室温截面

本文用X射线衍射法测定了Al-Ti-V-M四元系合金TiAl₃-VAl₃-MAI₃(M=Ni,Fe)两个赝三元系相图的室温截面。(1)TiAl₃-VAl₃NiAl₃赝三元系相图室温截面由一个单相点ε(NiAl₃)、一个单相区δ(TiAl₃和VAl₃形成的连续固溶体)和一个两相区δ+s所组成。(2)TiAl关键词：     

LiNaSO4-MgSO4赝二元系中离子导体的研究

本文用差热分析和X射线衍射方法,对LiNaSO₄-MgSO₄赝二元系相图进行了研究。在此体系中存在三个化合物,它们分别为(LiNa)_0.8Mg(0.2)SO₄,(LiNa)_0.67Mg_0.33SO₄和(LiNa)_0.4Mg_0.6SO₄。研究了三种化合物的离子导电性,在490℃时上述三个化合 关键词：     

Li3VO4-Li4SiO4-Li4GeO4赝三元系相图的研究

本文用差热分析法和高温、室温X射线衍射法对Li₃VO₄,Li₄SiO₄的相变过程,Li₃VO₄-Li₄SiO₄,Li₃O₄-Li-4GeO₄赝二元系相图以及Li₃VO₄-Li₄SiO₄-Li₄GeO₄赝三元系相图室温截面进行了研究。发现在Li₃VO₄-Li₄SiO₄,Li₃VO₄-Li₄GeO₄赝二元系中,由于Li₄SiO₄或Li₄GeO₄的加入而使Li₃VO₄的高温γ_II相稳定存在于室温,从而得到一种新的具有高电导率的锂离子导体。作者认为探寻使高温态稳定存在于室温的方法是探索新的离子导体研究中有效途径之一。 关键词：     

压力对NH4IO3及其固溶体相变的影响

在流体静压力到10kbar范围内,采用DTA技术研究了压力对NH₄IO₃及其固溶体K_x(NH₄)_1-xIO₃的相变温度(T_c)的影响。实验结果表明,虽然固溶体的相变温度T_c随K⁺组分的增加而减小,但是dT_c/dP值却同K⁺组分无关。这意味着在压力下IO₃^-离子的伸长对T_c随压力增加起主要作用。 关键词：     

BaO-Li2O-B2O3三元系中BaB2O4-Li2B2O4和BaB2O4-Li2O截面相平衡关系的研究

本文用X射线和差热分析方法对BaO-Li₂O-B₂O₃三元系中的两个截面:BaB₂O₄-Li₂B₂O₄和BaB₂O₄-Li₂O作了研究。在BaB₂O₄-Li₂B₂O₄赝二元系中发现了一个新的化合物4BaB₂O₄·Li₂B₂O₄。化合物在930±3℃由包晶反应形成,并与Li₂B₂O₄形成共晶反应。共晶温度为797±3℃,共晶点组分为79mol％Li₂B₂O₄。在BaB₂O₄-Li₂O截面中也存在化合物4BaB₂O₄·Li₂B₂O₄,其包晶反应温度从930±3℃随Li₂O含量增加下降到908±3℃。在组分60mol％Li₂O处形成另一个新的化合物2BaB₂O₄·3Li₂O。该化合物在630±3℃也是由包晶反应形成,并与Li₂O和Li₂CO₃分别形成共晶反应,共晶温度分别为400±3℃和612±3℃。在BaB₂O₄-Li₂B₂O₄和BaB₂O₄-Li₂O体系中都没有观察到固溶体。用计算机程序分别对化合物4BaB₂O₄·Li₂B₂O₄和2BaB₂O₄·3Li₂O的X射线粉末衍射图案进行了指标化,其结果:4BaB₂O₄·Li₂B₂O₄的空间群为Pmma,a=13.033?,b=14.630?,c=4.247?,每个单胞包含两个化合式单位;2BaB₂O₄·3Li₂O的空间群为Pmmm,a=4.814?,b=9.897?,c=11.523?,每个单胞也含有两个化合式单位。 关键词：     

Ba2CaWO6-Sr2CaWO6赝二元系的研究

用差热分析、X射线物相分析和点阵常数的精确测定,研究了Ba₂CaWO₆-Sr₂CaWO₆赝二元系的相平衡和相变。发现在高温(860℃以上)时,形成连续固溶体。在室温时,在富Ba₂CaWO₆一侧,形成以Ba₂CaWO₆为基的固溶体;在富Sr₂CaWO₆一侧,形成以Sr₂CaWO₆为基的固溶体,相变点在成分为Ba₂CaWO:Sr₂CaWO₆=25:75(克分子比)处。同时研究了作为高压钠灯灯丝涂层材料的Ba_xSr_2-xCaWO₆的几个重要性质:电子发射和多次启动时的灯压升高等。发现成分为BaSrCaWO₆时,性质最好。 关键词：     

LiIO3-Zn(IO3)2 赝二元系的研究

用固态粉末烧结法配制样品,用X射线衍射及差热分析等方法研究并测定了LiIO₃-Zn(IO₃)₂赝二元系的相图。该二元系内存在一新相LiZn(IO₃)₃。它有较大的倍频效应,具有离子导电性。用自编的由粉末衍射数据求单斜晶系的点阵参数的计算机程序成功地求出了该化合物的点阵常数。经过进一步修正,确定它属于正交晶系,α=8.08l?,b=8.729?,c=11.595?,z=4。并确定了化合物存在的成分范围和条件。 关键词：     

LiIO3-NaIO3赝二元系相图及其非晶态晶化动力学的研究

本文对LiIOO₃-NaIO₃赝二元系的相图,相变,非晶态的形成和稳定性,以及晶化的动力学过程等进行了仔细的研究,LiIO₃-NaIO₃赝二元系属共晶体系,共晶温度为325℃,共晶点成份为含50m/o LiIO₃,用共晶点附近成份的试样,在超过熔点150℃的情况下首次获得碘酸盐的非晶态,非晶态的存在降低了LiIO₃的表观相变温度,强X射线的辐照,各种空气湿度,细粒度等因素都加 关键词：     

赝二元固溶体TbGa1-xGex(0≤x≤0.4)的结构与磁性

采用电弧熔炼法在高纯氩气保护下合成了一系列TbGa_1-xGe_x(0≤x≤0.4)样品. X射线粉末衍射数据表明,样品均为正交晶系的CrB型结构,空间群为Cmcm. TbGa_1-xGe_x化合物的晶格常数随Ge含量的增加而线性减小,TbGa和TbGe赝二元系在0≤x≤0.4范围内形成固溶体. 化合物的顺磁居里温度以及有效磁矩由热磁测量结果确定. 相变温度由交流磁化率的测量获得. 随Ge含量的增加,化合物的相变温度单调下降. 变温X射线粉末衍射实验表明,x=0.2和0.3的样品在110—273K范围内无结构相变. 关键词： TbGa-TbGe 赝二元系 CrB结构 居里温度 磁化强度     

Quantitative Determination of Reactive Species in Alkali Halide Disks

Abstract

As part of an infrared investigation of the kinetics of the reactions of KMnO₄ in a KI disk and of KIO₄ in a KI disk, the stoichiometry of the two reactions was needed. A previous study¹ has shown that MnO₄ ^? reacts in a KI matrix to produce IO₄ ^? (which then reacts further to form IO₃ ^?) and MnO₂. Iodate ion is the only observable product in the reaction of IO₄ ^? in a KI matrix¹. The infrared absorption at 740cm^?1, which is due to the presence of IO₃ ^?, was found to obey the Beer-Lambert Law. However, calibration curves for KMnO₄ in KI and for KIO₄ in KI could not be obtained because both species reacted with the dispersing medium during the preparation of the disk¹. It was also observed that no immediate reaction occurred when KBr or KC1 disks containing KMnO₄, or KIO₄ were prepared. Thus, an extrapolation method was sought which would permit the estimation of calibration curves for the reactive species.     

The infra-red spectra of some ferroelectric compounds with short hydrogen bonds

The infra-red spectra of KH₂PO₄, NH₄H₂PO₄, NaH₂PO₄, KH₂AsO₄, NH₂H₂AsO₄, Ag₂H₃IO₆ and (NH₄)₂H₃IO₆ and of their deuterated analogues have been recorded at room temperature and some of them also at low temperature in the ferroelectric phase. The interpretation of the particularly interesting spectral region between 3000 and 1500 cm^?1, containing several OH bands, has been made in terms of the tunnelling of the protons between two minima of potential energy. These were taken to be of equal depth in the non-ferroelectric phase and unsymmetrical in the ferroelectric form. A quantum-mechanical treatment of the vibrational problem of the latter type has been carried out and is presented in the Appendix. Good agreement has been found between the theoretically predicted energy levels and the experimental data.     

Phase transitions and lattice dynamics in Ag2H3IO6 and (NH4)2H3IO6

The investigation of thermal, optical and dielectric properties of Ag₂H₃IO₆ and (NH₄)₂H₃IO₆ revealed phase transitions in two steps with unknown intermediate phases. Reflectivity measurements in the far infrared region confirm that the main step is caused by a freezing in of the proton tunnelling modes. From the results of NMR-NQR-spectroscopy the low temperature structures for both compounds are deduced. The complete group analysis of lattice vibrations and proton ordering modes of the room temperature phases is performed. In the case of Ag₂H₃IO₆ the transitions can be discussed in the frame-work of the Landau theory, starting with a condensation of an antiphase vibration of the silver atoms in theF point of the trigonal Brillouin zone, whereas in the case of (NH₄)₂H₃IO₆ a simultaneous ordering of protons inZ, F, andL-points of the Brillouin zone is proposed for the first step. A new definition of antiferroelectric transitions is suggested which is based on symmetry arguments only. The proton-ordering transitions in both compounds can then be classified as antiferroelectric.     

Mg(IO3)2-H2O体系的一个新物相Mg(IO3)2·2H2O和溶解度-温度相图

在Mg(IO₃)₂-H₂O体系中发现了一个新的物相二水碘酸镁Mg(IO₃)₂·2H₂O.用称重法测定了Mg(IO₃)₂,Mg(IO₃)₂·2H₂O和Mg(IO₂)₂·4H₂O的溶解度随温度变化的曲线。     

Structural phase transition in ferroelectric NH4103

The structural phase transformation between the ferroelectric and paraelectric form of NH₄IO, near 83°C is dominated by tilt motions of IO₆-octahedra within a perovskite-like framework. Simultaneously, small displacements of NH₄ along the polar axis give rise to a switchable spontaneous polarization at low temperatures. As the transition mechanism is governed by the tilting of octahedra and not by the appearance of ferroelectricity, NH₄IO₃ is characterised as an improper ferroelectric material. Although the space group of the high-temperature β-phase is polar, the polarization moment is zero. Raman-active thermal soft modes appear in the ferroelectric phase. The phase transition is first order with anomalies of dielectric, piezoelectric and elastic constants.     

Optical investigations of the effect of gradual substitution NH<Subscript>4</Subscript> → Cs on the ferroelastic phase transition in a CsLiSO<Subscript>4</Subscript> crystal

Crystals of Cs_x(NH₄)_1?xLiSO₄ (0.39≤x≤1.0) solid solutions are grown and investigated using polarized light microscopy and measurements of the birefringence in the temperature range 100–530 K. The (x-T) phase diagram of the Cs_x(NH₄)_1?xLiSO₄ solid solutions is constructed. It is demonstrated that, upon substitution of ammonium for cesium in the CsLiSO₄ crystal, the phase transition temperature gradually increases to such a degree that the ferroelastic phase can exist at room temperature. The triple point of intersection of the Pmcn, P2₁cn, and P112₁/n phase boundaries is determined. It is established that the introduction of ammonium in small amounts has an unusually strong effect on the refractive properties and character of the ferroelastic phase transition in the CsLiSO₄ crystal.