Insights into the direct formation of [Ca24Al28O64]4+(4e−) and its electrical characterization

C12A7:e⁻ electrides are potentially useful in various technological applications. However, it usually needs to be synthesized through a complicated multistep process under severe conditions. Therefore, the search is on for a more facile and direct process that occurs under milder conditions. Here, a facile and efficient synthesis strategy has been developed for the rapid production of highly conductive C12A7:e⁻ directly from commercially available chemical ingredients of CaO, Al₂O₃, and Al powders at 1200°C in a 10⁻² Pa vacuum for 20 minutes using SPS process. The electron concentration in the as-prepared C12A7:e⁻ was enhanced up to 2.13 × 10²¹ cm⁻³ by simply regulating the addition amounts of Al, covering IM transition. The electronic structure results indicated the formation of homogeneous trapped electrons in the lattice. Further thermal analyses illustrated that Al made a dual function of reducing agent and and reaction promoter, which remarkably reduced the formation temperature of mayenite structure. This study fills in the gaps of direct formation mechanisms of conductive mayenite phase, and provides a new perspective to regulate the resultant N_e.     

Fabrication and electron emission of [Ca24Al24.08Zr3.92O64]4+(4e−) electrides

[Ca₂₄Al_24.08Zr_3.92O₆₄]⁴⁺(4e⁻) electrides are ceramic materials with low work functions that can store high-density free electrons. So, it has great application potential in electron emission. In this paper, The mixed powders of CaO, Al₂O₃, ZrO₂, and Al in a certain stoichiometric ratio were used as precursors, and [Ca₂₄Al_24.08Zr_3.92O₆₄]⁴⁺(4e⁻) blocks were fabricated through in-situ reduction. The synthetic block samples have fewer pores, cracks, and impurities, and the blocks' relative density reaches 99.6%. At the same time, the blocks’ cages were injected with high-density electrons during the sintering, and the electron density reached 2 × 10²¹ cm⁻³. This makes the sample realize the transition from insulation to conductor. In addition, the block's emission current and effective work function is 1.75 A/cm² and 2.25 eV, respectively, at 1100°C. The research in this paper provides a new way for the low-cost and industrial production of high-quality [Ca₂₄Al_24.08Zr_3.92O₆₄]⁴⁺(4e⁻).     

[Ca24Al28O64]4+(4e−) are directly and quickly synthesized by self-reduction of C12H10Ca3O14 + Al2O3 without any reducing agent

C₁₂H₁₀Ca₃O₁₄ + Al₂O₃ powders are used as precursors, and the dense [Ca₂₄Al₂₈O₆₄]⁴⁺(4e⁻) (C12A7:e⁻) ceramic block with high electron density is quickly synthesized in one step under a spark plasma sintering (SPS) process with a temperature of 1000°C and a time of 5 minutes. The microstructure and composition analysis results show that the synthesized C12A7:e⁻ is dense (99.7%), has no defects, and no impurities are introduced. The electronic structure analysis results show that the electron concentration of the sample is 2 × 10²¹ cm⁻³. This method realizes the self-reduction of the sample through the CO gas generated during the sintering process, avoids the introduction of impurities, and dramatically simplifies the process. These results provide a potential path for the rapid fabrication of a large number of C12A7:e⁻ with high electron concentration and provide a basis for its practical applications such as cold cathode fluorescent lamp and catalyst carrier.     

掺Nd^3＋的[Y（Ca）]3[Al（Zr）]5O12石榴石单晶光纤的生长和光谱

用激光加热基座法（ＬＨＰＧ）从粉末直接生长单晶光纤并对光谱作了研究。结果表明：ＬＨＰＧ法生长出来的单晶光纤可替代大块晶体去研究光谱等性能；Ｃａ＾２＋和Ｚｒ＾４＋等量同时掺入到Ｎｄ：ＹＡＧ晶体中，其吸收谱与Ｎｄ：ＹＡＧ基本相同，但荧光分支比和荧光衰减规律发生显著变化。此外还探讨了Ｃａ＾２＋，Ｚｒ＾４＋影响的原因。     

A new sandwich-type polyoxometalate constructed from penta-lacunary [HPW7O28]8− units and MnIII ion

A new sandwich-type polyoxometalate (POM) K₁₂Na₁[(HPW₇O₂₈)₂Mn]·17.5H₂O (1) has been synthesized and characterized by elemental analysis, IR, TG, UV as well as single-crystal X-ray diffraction analysis. Compound 1 represents the first sandwich-type POM constructed by the penta-lacunary heptatungstophosphate [HPW₇O₂₈]^8? moieties. Moreover, compound 1 exhibits good electrocatalytic properties to reduce the nitrite.     

In vacuo production of α-AlB12, C4AlB24, AlB12C2 and Al3B48C2 powders

The production of pure powder samples of boron-rich ternary Al–B–C phases was investigated in vacuum at temperatures between 1400 °C and 1600 °C, using a range of different starting powders. Compacted powder mixes of B–AlB₂–B₄C, Al–B–C, Al–B–B₄C, B–C–AlB₂, B–AlB₂ and Al–B were heated for 1–2 h under vacuum in a carbon resistance furnace and the products characterised by X-ray diffraction. It was found impossible to produce significant quantities of C₄AlB₂₄ under these conditions, but >95% pure samples of α-AlB₁₂, AlB₁₂C₂ and Al₃B₄₈C₂ were obtained. This study is a precursor to further research aimed at producing dense B₄C-type materials which might offer the advantages of easier densification and fabrication as compared with B₄C itself.     

Synthesis and proton conductivity of a new two-dimensional layered aluminophosphate [C9H14N]8[H2O]4·[Al8P12O48H4]

A new two-dimensional layered aluminophosphate [C₉H₁₄N]₈[H₂O]₄·[Al₈P₁₂O₄₈H₄] (denoted as AlPO-CJ70) has been synthesized by using N,N-dimethylbenzylamine as the template under solvothermal conditions at 403 K. Single-crystal X-ray diffraction analysis reveals that the structure of AlPO-CJ70 consists of AAAA-stacked Al₂P₃O₁₂^3 − layers made of alternating AlO₄ and PO₄ (PO₃(O) and PO₂(O)(OH)) tetrahedra, forming 1D 8-ring channels along the [100] direction. The inorganic layer exhibits a new type of 4 × 6 × 8 sheets with the Al/P ratio of 2/3. Protonated N,N-dimethylbenzylamine cations are located between the layers compensating the negative charge of the anionic framework. The existence of guest water and extensive H-bonds in the structure endows AlPO-CJ70 with proton conduction properties, as elucidated by impedance studies of the powder sample.     

C3S-C12A7-H2O和C3S-C12A7-CaSO4·2H2O-H2O系统的水化及其性能研究

试验用结合水法、化学减缩法、XRD定量等物理、化学分析方法 ,研究了C1 2 A7和石膏同时存在时C3S在不同系统中的水化动力学及水化机理。结果表明C1 2 A7能够促进C3S的水化 ,尤其是对C3S早期水化有显著的促进作用 ;当有石膏存在时 ,这种促进作用更为显著。其机理是由于C1 2 A7水解放出的Al(OH) - 4 与C3S水解放出的Ca2 反应生成C3AH6 ,当有石膏存在时 ,生成钙钒石 ,从而加快了C3S的水化。研究得出了C3S在不同系统中的水化动力学方程     

A comparison study on the substitution of Y3+−Al3+ by M2+−Si4+(M = Ba,Sr, Ca,Mg) in Y3Al5O12: Ce3+ phosphor

Y_1.94MAl₄SiO₁₂:0.06Ce³⁺ (M = Ba, Sr, Ca, Mg) phosphors were successfully prepared through a classic solid-state reaction method. The crystal structures, photoluminescence spectra, quantum yields, and thermal stabilities of the phosphors were investigated in detail. The results indicate that all Y_1.94MAl₄SiO₁₂:0.06Ce³⁺ phosphors maintain the crystal structure of garnets. The emission peaks of Y_1.94MAl₄SiO₁₂:0.06Ce³⁺ (M = Ba, Sr, Ca, Mg) phosphors are located at 537, 538, 554, and 565 nm, respectively. A red-shift trend of emission peak is observed with decreasing M radius, which can be ascribed to the increase in the crystal-field splitting in the Ce³⁺ 5d level owing to the co-doping of M²⁺−Si⁴⁺. Under 460 nm excitation, the luminescence quantum yields and thermal stabilities of the Y_1.94MAl₄SiO₁₂:0.06Ce³⁺ phosphors decreased with the decrease of M radius. The IQE of the Y_1.94BaAl₄SiO₁₂:0.06Ce³⁺ phosphor is 92.89%, and the resistance to thermal quenching is improved to be 93.32% at 150°C. In addition, the color shifts of Y_1.94MAl₄SiO₁₂: 0.06Ce³⁺ phosphors with increasing temperature are all tiny, which also demonstrates good resistance to thermal quenching of luminescence. The linear shrinkage of Y_1.94MAl₄SiO₁₂:0.06Ce³⁺ phosphors is significantly improved compared with that of YAG: Ce³⁺, which is expected to generate Y_1.94MAl₄SiO₁₂:0.06Ce³⁺ transparent/translucent ceramics and fabricate high-powder w-LEDs for high-quality solid-state lighting in the future.     

A 3D oxalate-bridged [CuIIFeII] coordination polymer as molecular precursor for CuFe2O4 spinel—photocatalytic features

A 3D heterometallic oxalate-bridged coordination polymer [Cu^IIFe^II₂(H₂O)(terpy)(C₂O₄)₃]_n (terpy = 2,2′:6′,2″-terpyridine) ( 1 ) was investigated both as photocatalyst for the organic dye removal and as a single-source precursor for the preparation of the copper ferrite (CuFe₂O₄) nanocrystals by thermal processing. The dual functionality of 1 was supported by the degradation of aqueous solutions of rhodamine B (RhB) and methylene blue (MB) solutions under visible (Vis) and ultraviolet (UV) light irradiation, powder X-ray diffraction data collection at room temperature, and the optical and scanning electron microscopy analyses. A close inspection of the X-ray diffraction patterns unveiled qualitative and quantitative information on the phase composition obtained after the single-source molecular precursor route to spinel oxide. By optimizing the temperature levels and setting the controlled heating rate at 6 h of holding time, the phase composition of thermal processing of 1 was evaluated—thermal treatment of 1 at 950°C for 6 h and a heating/cooling rate of 10°C min⁻¹ resulted in the formation of solely tetragonal spinel phase of CuFe₂O₄, whereas the formation of both tetragonal and cubic CuFe₂O₄ phases was observed at 950°C by the heating rate of 30°C min⁻¹. To obtain the high-temperature cubic CuFe₂O₄ oxide, compound 1 was heated and then quenched at 925°C, which led to the formation of the cubic spinel ferrite as the main crystalline oxide phase. Moreover, the photocatalytic properties of the t-CuFe₂O₄ spinel were investigated under the same conditions as for 1 . The optical bandgap energies were estimated from UV–Vis absorption spectra for both metal oxide and precursor powder.     

A new polymeric chain in the dihydrogendecavanadate(V)–decavanadate(V) [NH2(CH2)4]5[V10O28H2]0.5[V10O28]0.5 obtained by in situ synthesis of the organic cation

A new polymeric compound, [NH₂(CH₂)₄]₅[V₁₀O₂₈H₂]_0.5[V₁₀O₂₈]_0.5, was obtained by in situ synthesis of the organic cation from an aqueous solution of V₂O₅–HCl–NH₂(CH₂)₄NH₂. The crystal structure was solved by single-crystal X-ray diffraction. [NH₂(CH₂)₄]₅[V₁₀O₂₈H₂]_0.5[V₁₀O₂₈]_0.5 consists of dihydrogendecavanadate(V), [H₂V₁₀O₂₈]^4?, and decavanadate(V), [V₁₀O₂₈]^6?, units assembled in one-dimensional arrays by interanionic hydrogen bonds O–H?O and cation-anion N–H?O interactions. The latter involve pyrrolidinium cations, which were obtained in the compound instead of the starting butane-1,4-diamine. Pyrrolidinium cations further connect the polymeric chains into a three-dimensional network. The presence of the two types of units, [H_nV₁₀O₂₈]^(6?n)? with n = 0 and n = 2, in one compound was not yet observed and is herein reported for the first time.     

[PW12O40]（C2N3H4）3·6H2O的水热合成和晶体结构

在水热条件下,合成出一例新的具有Keggin型结构的杂多酸化合物[PW12O40]（C2N3H4）3·6H2O（1）。利用单晶X-射线衍射分析了该化合物的结构,结果表明该化合物属于三方晶系,R-3空间群,晶胞参数为a=1.79590（3）nm,b=1.79590（3）nm,c=2.43480（5）nm,α=90°,β=90°,γ=120°,V=6.8008（2）nm3,Z=6,R1=0.0458,ωR2=0.1116。在该化合物中,质子化的1,2,4-三氮唑与[PW12O40]3-通过氢键作用形成三维超分子结构。     

Structural studies on Ca3Al4MgO10 (C3A2M)—A ternary phase in the system CaO–Al2O3–MgO

In a sequence of temperature-dependent solid-state reactions in the system CaO–Al₂O₃–MgO the formation of the ternary phase Ca₃Al₄MgO₁₀ or C₃A₂M has been studied. Whereas the compound could not be prepared at 1200°C, a yield of 85 wt.-% of Ca₃Al₄MgO₁₀ was obtained at 1320°C (incongruent melting point: 1330°C). Powder diffraction data compare well with results of previous investigations from the 1960s. Single crystals of Ca₃Al₄MgO₁₀ could be retrieved from the sinter-pellets. Basic crystallographic data are as follows: orthorhombic symmetry, space group Pbcm, a = 5.14073(8), b = 16.7576(2), c = 10.70977(16) Å, V = 922.61(2) ų, Z = 4. Using synchrotron diffraction data it was possible to solve the crystal structure. Least-squares refinements resulted in a residual of R(|F|) = 0.021 for 1000 independent observed reflections with I > 2σ(I) and 97 parameters. The structure contains [TO₄]-tetrahedra (T=Al,Mg) forming a three-dimensional (3-D) framework whose topological characteristics have been determined. Al-Mg distributions on the different T-sites have been studied. The calcium cations are located in voids of the network. More than 50 years after its first observation our investigation clarifies the crystal structure of a compound belonging to a system that is of relevance for several fields of materials science.     

Synthesis and nanostructure of [Mo(C6H4O2)3]·2(C4H8N2O) and the synthesis from 1,2-PDA to (C4H8N2O)

Continuing our work on the synthesis of MoO₂L₂ and MoO₃L_AL_B that show excellent anti-cancer activities in vitro, the MoL₃ have been synthesized by the solvothermal reaction of Na₂MoO₄ with catechols and 1,2-DPA in the mixed solvent of MeCN/MeOH. X-ray diffraction revealed that Mo in chiral octahedral geometry coordinate with three catechol ligands formed three five-membered rings, and the [Mo(C₆H₄O₂)₃] are linked by hydrogen bonds Mo(OC₆H₄)O…H–N(C₄H₈O)N–H…O(C₆H₄O)Mo through the by-product (C₄H₈N₂O) that are formed by one 1,2-DPA with one CO₂ on the catalysis of Mo-complex. Also, we have disassembled bulk crystal into nano-aggregates, and under TEM mono-lamella morphology of nanostructures was observed, which agrees well with the previous conclusion that the morphologies of the nano-aggregates are associated with the quantum motifs in their crystal lattices. [Mo(C₆H₄O₂)₃] have also been characterized by UV–vis spectra, cyclic voltammogram and thermogravimetric analysis.     

A novel 12-tungstovanadate and 3d–4d heterometallic complex hybrid compound [V1W12O40][VO2Ag(phen)3]2

A novel organic–inorganic hybrid compounds containing 12-tungstovanadate and 3d–4d heterometallic complex, [V₁W₁₂O₄₀][VO₂Ag(phen)₃]₂ (1), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction and IR analysis. The complex is an uncommon bisupporting polyoxometalate derivative in which the saturated Keggin type polyoxoanions are covalently linked by bimetallic complex [VO₂Ag(phen)₃]²⁺. The neighboring Ag⁺ and V⁵⁺ cations are bridged by the oxo atom forming heterometallic cations with the Ag–V distances of 3.556(2) Å in [VO₂Ag(phen)₃]²⁺ cations. Furthermore, the title compound shows good photocatalytic activity for reduction of Rhodamine B (RB) in a liquid–solid system.     

Formation of strontium-yttrium germanium anionic lacunar apatite (Sr2+δY6.67+(2δ/3)[GeO4]6O2δ) as the intermediate phase of oxygen-rich yttrium-germanium apatite (Y9.333+ε[GeO4]6O2+3/2ε)

The formation of metastable strontium-yttrium(III) (hexakis) germanium(IV) lacunar apatite (P6₃/m, a=11.426 Å, c=8.224 Å and Z=2) was observed during the thermal treatment of SrCO₃, Y₂O₃, and GeO₂ powder precursors using the ceramic method in an oxygen atmosphere. The utilization of an oxygen atmosphere restricts the extensive reduction of GeO₂ and enables us to explain a new potential mechanism for the stabilization of lead-free lacunar apatites. This mechanism involves the use of electrons localized in a neighborhood of oxygen vacancies. Charged vacancies serve as active sites for the ionosorption of oxygen molecules and their subsequent transformation into lattice oxygen anions, which fill the vacancies at the X-site. The estimation of system thermodynamics shows that apatite undergoes a transformation to a more stable state at δ≥0.1, i.e., at the value that corresponds to the composition of prepared apatite. As the temperature and time of the thermal treatment increases, the process of incongruent melting leads to the formation of oxygen-rich yttrium-germanium apatite (YGAp, Y_9.333+ε[GeO₄]₆O_2+3/2ε) and strontium-yttrium-germanium glass. The YGAp phase is also formed during the annealing of lacunar apatite in an oxygen atmosphere.