Thermal Analysis of the System Na3AlF6–NaVO3

Summary. The phase diagram of the system Na₃AlF₆–NaVO₃ was determined by means of thermal analysis. The system is a simple binary eutectic one. The eutectic point was estimated at x(NaVO₃) = 0.975 and t _eut = 617°C. The XRD patterns of samples after thermal analysis revealed the presence of cryolite and NaVO₃ only supporting the above assumption of a simple eutectic binary system.     

Phasenbeziehungen und Natriumionenleitung im quasi-binären System Na2SiF6/Na3AlF6

Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na₂SiF₆/Na₂AIF₆ . The phase diagram of the Na₂SiF₆/Na₃AlF₆ system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na₃AlF₆ accomodates up to 73 mol.-% Na₂SiF₆ maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na₃AlF₆ with Na₂SiF₆.     

Experimental Binary Phase Diagram of Bilayer Compounds [n-CnH2n+1N(CH3)3]2CoCl4

Compounds [n-C_nH_2n+1N(CH₃)₃]₂CoCl₄(n=16, C₁₆C₃Co; n=18, C₁₈C₃Co) containing lipid-like bilayers embedded in a crystalline matrix exist in solid-solid phase transition. The low-temperature bilayer structures of the two compounds were organized by neutralizing CoCl₄^2- with alkylammonium ions. Alkyl chains lay parallel to each other and slightly tilted with respect to the normal of the inorganic layers. The adjacent alkyl chains interacted with each other by van der Waals interaction. When the temperature increased, the two compounds underwent a reversible solid-solid phase transformation within 310―330 K. In such a case, the chains showed a large motional freedom, and a disordered phase appeared. The structures can alternatively be viewed as a double layer of alkylammonium ions between CoCl₄^2- sheets and be considered as crystalline models of lipid bilayers. The experimental subsolidus binary phase diagram of [n-C₁₆H₃₃N(CH₃)₃]₂CoCl₄-[n-C₁₈H₃₇N(CH₃)₃]₂CoCl₄ was constructed over the entire composition range by differential scanning calorimetry and X-ray diffraction technique. Experimental phase diagram indicates one stable intermediate phase [n-C₁₆H₃₃N(CH₃)₃][n-C₁₈H₃₇N(CH₃)₃]CoCl₄ at w_C16C3Co= 39.89% and two invariant three- phase equilibria, which shows two eutectoid temperatures: T_e1 at (316±1) K for w_C16C3Co= 27.35% and T_e2 at (313±1) K for w_C16C3Co=59.76%. These three noticeable solid-solution ranges are α-phase at the left, β-phase at the right, and γ-phase in the middle of the phase diagram.     

LaX3-C18H16N3O2Cl-H2O三元体系的相平衡

测定了ＬａＸ３－Ｃ１８Ｈ１６Ｎ３Ｏ２Ｃｌ－Ｈ２Ｏ（Ｘ＝ＮＯ＾３,Ｃｌ＾－）三元体系在３０℃时的溶度和饱和溶液的折光率。发现Ｌａ（ＮＯ３）３＝Ｃ１８Ｈ１６Ｎ３Ｏ２Ｃｌ－Ｈ２Ｏ体系有不一致溶化合物Ｌａ（Ｃ１８Ｈ１６Ｎ３Ｏ２Ｃｌ）３（ＮＯ３）３生成,而ＬａＣｌ３－Ｃ１８Ｈ１６Ｎ３Ｏ２Ｃｌ－Ｈ２Ｏ体系为简单共饱体系。     

273 K下Na2CO3-Na2SO4-Na2B4O7-H2O四元体系介稳相平衡的实验研究

采用等温蒸发法研究了四元体系Na2CO3-Na2SO4-Na2B4O7-H2O在273 K时的介稳相平衡及平衡液相的密度. 利用溶解度数据绘制了该四元体系273 K下的相图. 研究结果表明, 该四元体系有异成分复盐2Na2SO4·Na2CO3形成. 相图中有2个共饱点、5条单变量曲线和4个结晶相区. 4个结晶相区分别为盐Na2CO3·10H2O, Na2SO4·10H2O, Na2B4O7·10H2O和2Na2SO4·Na2CO3的结晶区. 复盐2Na2SO4·Na2CO3同时存在于包含Na2CO3-Na2SO4-H2O三元体系的其它四元体系或高元体系中. 在273 K介稳平衡相图中, 碳酸钠以Na2CO3·10H2O形式析出; 硫酸钠以Na2SO4·10H2O的形式析出; 硼酸钠的完整分子式为Na2B4O5(OH)4·8H2O. Na2CO3对Na2B4O7有盐析作用.     

仲钨酸钠的热分解研究

制备了仲钨酸钠Na（10）H2W（12）O（42）·27H2O，用X射线衍射、Raman光谱及化学分析进行了表征．热分析的研究表明：该化合物热分解过程包括六个步骤．其中前四步为脱水步骤，温度分别为331，353，403及588K左右，而失水数分别为10H2O，9H2O，5H2O及4H2O；第五步可能为中间产物的相转变，温度为691K左右，第六步生成Na2W2O7和Na2W4O（13）的混合物，温度为733K左右．前五步中每一步的产物在标题化合物馆和溶液的气相中平衡处理之后，又都能得到标题化合物．     

Sodium Trinitratouranylate(VI) Na[UO2(NO3)3]

Although potassium, rubidium, and cesium uranyl nitrate have been characterized a long time ago, the crystal structure and properties of the homologous sodium compounds has not been reported yet. Na[UO₂(NO₃)₃] crystallizes in a unique structure [Pearson code cP72, cubic, P2₁3, no. 198, Z = 4, a = 10.6324(14) Å, 938 unique reflections with I_o > 2σ(I_o), R₁ = 0.0379, wR₂ = 0.0947, GooF = 1.092, T = 293 K]. The structure is characterized by an open framework built by interconnected helical chains formed by {UO₈} and {NaO₆} units. The vibrational and optical (UV/Vis absorption and luminescence) spectra match well with those of the higher alkali metal uranyl nitrates.     

Multimode Luminescence Tailoring and Improvement of Cs2NaHoCl6 Cryolite Crystals via Sb3+/Yb3+ Alloying for Versatile Photoelectric Applications

Lead-free halide double perovskites are currently gaining significant attention owing to their exceptional environmental friendliness, structural adjustability as well as self-trapped exciton emission. However, stable and efficient double perovskite with multimode luminescence and tunable spectra are still urgently needed for multifunctional photoelectric application. Herein, holmium based cryolite materials (Cs₂NaHoCl₆) with anti-thermal quenching and multimode photoluminescence were successfully synthesized. By the further alloying of Sb³⁺ (s-p transitions) and Yb³⁺ (f-f transitions) ions, its luminescence properties can be well modulated, originating from tailoring band gap structure and enriching electron transition channels. Upon Sb³⁺ substitution in Cs₂NaHoCl₆, additional absorption peaking at 334 nm results in the tremendous increase of photoluminescence quantum yield (PLQY). Meanwhile, not only the typical NIR emission around 980 nm of Ho³⁺ is enhanced, but also the red and NIR emissions show a diverse range of anti-thermal quenching photoluminescence behaviors. Furthermore, through designing Yb³⁺ doping, the up-conversion photoluminescence can be triggered by changing excitation laser power density (yellow-to-orange) and Yb³⁺ doping concentration (red-to-green). Through a combined experimental-theoretical approach, the related luminescence mechanism is revealed. In general, by alloying Sb³⁺/Yb³⁺ in Cs₂NaHoCl₆, abundant energy level ladders are constructed and more luminescence modes are derived, demonstrating great potential in multifunctional photoelectric applications.     

Phase Transitions in Three New Hybrid Crystals: (Me3NR)4[Ni(NCS)6] (R=Ethyl,Propyl, and Butyl)

Understanding the microscopic origin of phase transitions in hybrid crystals is of significant important but challenging for designing novel phase-transition materials. Here, three new hybrid crystals, (Me₃NR)₄[Ni(NCS)₆] (R=ethyl for 1 , propyl for 2 , and butyl for 3 ) were synthesized and comprehensively studied on their crystal structures, intermolecular interactions, and phase transitions. They possess a same anti-XeF₄ structure mode but exhibit different phase transitions arising from their subtly changed alkyl groups. Specifically, 1 undergoes four-step P2₁/c-P2₁/c-P2₁/c-Pbca-Cmce crystalline transitions at 165, 203, 244, and 280 K, respectively; 2 undergoes three-step P2₁2₁2₁-Pbca-P2₁/n-P 1c crystalline transitions at 167, 393, and 410 K, respectively, following by a solid-liquid transition at 453 K; 3 undergoes an iso-space-group P2₁/n-P2₁/n crystalline phase transition at 257 K and a solid-liquid transition at 410 K. These instances well demonstrate the key roles of delicate and complicated intermolecular interactions on inducing nontrivial phase transitions in hybrid crystals.     

CO(NH2)2-H3BO3-H2O体系相平衡研究

农作物不仅需要吸收C、H、O、N、P、K、Ca、Mg等营养元素,而且还需要吸收B、Mn、Zn等营养元素,以维持它们正常生长的需要.尿素是一种含氮量很高(46.60%)、性能很好的氮肥,而硼化合物又是一种很重要的微量元素肥料.因此,研究尿素与硼化合物间的相互作用,以得到既含氮又含硼的一种化合物,是一种很有意义的工作。目前,国外已开展了尿素与硼酸间相互作用的研究工作.研究结果表明,在一定条     

A New Sodium Borate: Na[B6O8(OH)3]·6H2O·H3BO3

The structure of [B₆H₉NaO₁₄, H₃BO₃, 6H₂O] was determined by single‐crystal X‐ray diffraction and further analyzed by FTIR spectroscopy and differential thermal/thermogravimetric analysis. The asymmetric unit contains Na–O polyhedra (distorted octahedron), [B₆O₈(OH)₃]^– fundamental building blocks, one free water molecule and one free H₃BO₃ molecule. In the hexaborate anion, three B₃O₃ rings are linked by a common oxygen atom with five trigonal and one tetrahedral boron atoms. The hexaborate group is also linked to the oxygenated environment of the sodium atom by three other six‐membered rings, each of which involve two boron atoms, three oxygen atoms, and sodium as the joint atom.     

EuI2—LiI和EuI2—NaI二元体系相图

用ＤＴＡ和Ｘ射线粉末衍射法研究了ＥｕＩ２－ＮａＩ和ＥｕＩ２－ＬｉＩ两个二元体系低压相图。ＥｕＩ２－ＮａＩ二元体系相图为一简单低共熔相图，低共熔点为４０９℃，其低共熔摩尔组成为３２％ＮａＩ；ＥｕＩ２－ＬｉＩ体系相图也为一简单低共熔相图。低共熔点为３８５℃，低共熔摩尔组成为６８．５％ＬｉＩ。     

Experimental Investigation on Binary Phase Diagram of the Thermotropic Phase Transitions Compounds (n‐CnH2n+1R3)2ZnCl4

The thermotropic phase transitions compounds (n‐C_nH_2n+1R₃)₂ZnCl₄ as well as a series of their binary mixtures were prepared by a solution reflux method from their ethanol solutions. The experimental subsolidus binary phase diagram of [n‐C₁₈H₃₇N(CH₃)₃]₂ZnCl₄‐[n‐(C₁₈H₃₇)₂N(CH₃)₂]₂ZnCl₄ is constructed over the entire composition range by differential scanning calorimetry(DSC) and X‐ray. Experi‐ mental results indicate one stable intermediate phase [n‐C₁₈H₃₇N(CH₃)₃] [n‐(C₁₈H₃₇)₂N(CH₃)₂]ZnCl₄ at W_C18C3Zn %=59.75 %, and two invariant three phase equilibria, which shows two eutectoid temperatures: Te₁ at 310±1 K for eutectoid point W_C18C3Zn %=36.24 %, Te₂ at 313±1 K for eutectoid point W_C18C3Zn %=80.17 %. These three noticeable solid‐solution ranges are α‐phase at the left, ?‐phase at the right, and ψ‐phase in the middle of the phase diagram. It is (n‐C_nH_2n+1R₃)₂ZnCl₄ systems as phase change materials that are characterized the phase transition temperatures T in the range of 310 to 340 K, the transition enthalpies ΔH in the range of 38.40 and 168.72 J/g between two polymorphic forms.     

Crystal Structure,Thermal and Electric Behaviour of [(CH3)2NH2]3[As2Cl9] and [(CH3)2NH2][AsOCl2]

Single crystals of the organic‐inorganic arsenate(III): [(CH₃)₂NH₂]₃[As₂Cl₉] and [(CH₃)₂NH₂][AsOCl₂] have been grown from aqueous hydrochloric acid solution. The crystals [(CH₃)₂NH₂]₃[As₂Cl₉] have been investigated by X‐ray diffraction (at 253 K), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dilatometric and dielectric methods. They undergo two structural phase transitions of first order at 228/235 and 298/307 K (on cooling/heating), respectively, which are classified as an "order‐disorder" type. The trigonal [(CH₃)₂NH₂]₃[As₂Cl₉] structure (at 253 K, intermediate phase (II)) refined in the space group R3c, consists of isolated [As₂Cl₉]^3‐ bioctahedral units and dimethylammonium cations hydrogen bonded to the bridging Cl atoms of the anions. The crystals of [(CH₃)₂NH₂][AsOCl₂] at 100 K are orthorhombic, space group Cmca. The structure contains one‐dimensional chains formed by strong distorted [AsO₂Cl₄] octahedra. The dimethylammonium cations reveal distinct disorder.     

Sodium Salts of the Bipyridine Dianion: Polymer [(bpy)2−{Na+(dme)}2]∞, Cluster [(Na8O)6+Na+6(bpy)62−(tmeda)6], and Monomer [(bpy)2−{Na+(pmdta)}2]

Bipyridine, a workhorse among the ligands of complex chemistry, can be reduced with sodium to its dianion. Depending on the solvent different sodium salts crystallize: from dimethoxyethane/toluene a polymer, from tetramethylethylenediamine/benzene a lipophilically wrapped [Na₁₄O]¹²⁺ cluster, and from pure pentamethyldiethylenetriamine a normal Na₂-bpy salt (see picture) are obtained.     

Revised Phase Diagram of the System NaF–NaBF4

Summary. The phase diagram of the binary system NaF–NaBF₄ was determined using the thermal analysis method. Subsequent coupled analysis of the thermodynamic and phase diagram data was carried out to calculate the thermodynamically consistent phase diagram. The system NaF–NaBF₄ forms a simple eutectic phase diagram with the calculated coordinates of the eutectic point: 8.1 mol% NaF, 91.9 mol% NaBF₄, and 385.7°C. The probable inaccuracy in the calculated binary phase diagram is 9°C.     

Nitrogen-doped Carbon Coated Na3V2(PO4)3 with Superior Sodium Storage Capability

Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application. Na₃V₂(PO₄)₃ is an attractive cathode material with excellent electrochemical stability and fast ion diffusion coefficient within the 3D NASICON structure. Nevertheless, the practical application of Na₃V₂(PO₄)₃ is seriously hindered by its intrinsically poor electronic conductivity. Herein, solvent evaporation method is presented to obtain the nitrogen-doped carbon coated Na₃V₂(PO₄)₃ cathode material, delivering enhanced electrochemical performances. N-Doped carbon layer coating serves as a highly conducting pathway, and creates numerous extrinsic defects and active sites, which can facilitate the storage and diffusion of Na⁺. Moreover, the N-doped carbon layer can provide a stable framework to accommodate the agglomeration of the electrode upon electrode cycling. N-Doped carbon coated Na₃V₂(PO₄)₃(NC-NVP) exhibits excellent long cycling life and superior rate performances than bare Na₃V₂(PO₄)₃ without carbon coating. NC-NVP delivers a stable capacity of 95.9 mA·h/g after 500 cycles at 1 C rate, which corresponds to high capacity retention(94.6%) with respect to the initial capacity(101.4 mA·h/g). Over 91.3% of the initial capacity is retained after 500 cycles at 5 C, and the capacity can reach 85 mA·h/g at 30 C rate.     

SmI2-KI二元体系相图的研究

运用DTA差热分析法和X射线衍射粉末法研究了Sml₂-KI二元体系等压相图及该体系中KSm₂I_s,K₂SmI₄的性质和结构.借助J.Kutscher讨论REX₃-AX(RE=稀土,A=碱金属)体系形成化合物规律的方法,对SmI₂-AI,YbI₂-AI(A=Na,K,Rb,Cs)两个系列形成的规律进行了初步讨论。     

烟酸钠Na(C6H4NO2)(s)的低温热容和热化学

选择分析纯烟酸和无水醋酸钠作为反应物, 用室温固相合成方法合成了无水烟酸钠. 利用FTIR和X射线粉末衍射等方法进行了表征, 利用化学分析和元素分析确定其组成为Na(C6H4NO2). 用精密自动绝热热量计测量其在78~400 K温度区间的低温热容. 研究结果表明, 该化合物在此温度区间无热异常现象发生. 用最小二乘法将实验摩尔热容对温度进行拟合, 得到热容随温度变化的多项式方程. 用此方程进行数值积分, 得到在此温度区间每隔5 K的舒平热容值和相对于298.15 K时的热力学函数值. 在此基础上, 通过设计合理的热化学循环, 选用1 mol/L NaOH溶液作为量热溶剂, 利用等温环境溶解-反应热量计分别测得固相反应的反应物和产物在所选溶剂中的溶解焓, 得到固相反应的反应焓. 最后, 计算出无水烟酸钠的标准摩尔生成焓为: ΔfHm0[Na(C6H4NO2), s]=-(548.96±1.11) kJ/mol.