Structure Prediction of Binary Pernitride MN2 Compounds (M=Ca,Sr, Ba,La, and Ti)

Metal‐pernitride compounds belong to a class of chemical systems in which both the complex ions and the non‐bonding electrons may play roles in the formation of their modified crystalline structures. To investigate this issue, the energy landscapes of pernitrides of metals with different maximum valence (M=Ca, Sr, Ba, La, and Ti) were globally explored on the ab initio level at standard and high pressures, thereby yielding possible (meta)stable modifications in these systems together with information on how the landscape changed as function of the valence of the metal cation. For all of the systems in which no compounds had been synthesized so far, we predicted the existence of kinetically stable modifications that should, in principle, be experimentally accessible. In particular, TiN₂ should crystallize in a new structure type, TiN₂‐I.     

ChemInform Abstract: Structure Prediction of Binary Pernitride MN2 Compounds (M: Ca,Sr, Ba,La, and Ti)

Based on ab initio calculations at various pressures meta(stable) modifications of CaN₂, LaN₂, and TiN₂ are predicted.     

MZrO3（M=Ba,Sr,Ca）水热合成中结构与反应活性的关系

ＭＺｒＯ_３（Ｍ＝Ｂａ，Ｓｒ，Ｃａ）水热合成中结构与反应活性的关系郑文君，庞文琴（吉林大学化学系，长春，１３００２３）关键词水热合成，ＭＺｒＯ_３（Ｍ＝Ｂａ，Ｓｒ，Ｃａ），结构，反应活性钙钛矿型复合氧化物ＭＺｒＯ３（Ｍ＝Ｂａ，Ｓｒ，Ｃａ）是重要的功能陶...     

Phase Analysis and Crystallographic Properties of the Phosphate Systems MO-ZrO2-P2O5 (M=Mg,Ca, Sr or Ba)

Phase formation in the systems MO-ZrO₂-P₂O₅ (M=Mg, Ca, Sr or Ba) with various ratios of M to Zr cations and within the temperature interval from 20 to 1200°C was investigated by means of DTA, TG, XRD and IR spectroscopy. The orthophosphate phases M_0.5xZr_2.25−0.25x(PO₄)₃ with x=0−1, 3 and 7 were synthesized. Concentration and temperature limits of phase existence were found for phosphates belonging in the NaZr₂(PO₄)₃ structural family. They exist within the regions with M to Zr ratios of 0≤x≤1 (with the exception of the Mg phases) and in the temperature interval from room temperature to 900–1700°C. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sonochemical Synthesis and Photocatalytic Properties of Metal Hydroxide and Carbonate (M:Mg, Ca, Sr or Ba) Nanoparticles

In this work Mg(OH)₂, Ca(OH)₂, CaCO₃, SrCO₃ and BaCO₃ nanoparticles were synthesized via a simple sonochemical reaction at room temperature. Nanoparticles were synthesized via a surfactant-free reaction solvent water. Nanostructures materials were characterized by scanning electron microscopy, X-ray diffraction and fourier transform infrared spectroscopy. The photocatalytic behavior of nanoparticles was evaluated using the degradation of a methyl orange aqueous solution under ultraviolet light irradiation. The results show that metal hydroxide and metal carbonate nanoparticles are promising materials with excellent performance in photocatalytic applications.     

Ternary phases MPtSi (M = Ca,Eu, Sr,Ba) with the LalrSi-type structure

Four ternary phases MPtSi (M = Ca, Eu, Sr, Ba) have been shown to crystallize in the LaIrSi-type structure (space group P2₁3). This ternary structure is a derivative structure of the binary SrSi₂-type structure (space group P4₃32 or P4₁32). In the MPtSi series the LaIrSi-type structure has a stability range for metals with radii from r_Ca = 1.973 Å to r_Ba = 2.243 Å in contrast to MSi₂ compounds which exist with the SrSi₂-type structure only from r_Sr = 2.151Å to r_Ba 2.243 Å. From a single-crystal investigation on CaPtSi remarkably short PtSi distances of 2.30 Å (3x) are obtained. Structural relations are discussed.     

Perovskite Distortion Inverted: Crystal Structures of (A3N)As (A = Mg,Ca, Sr,Ba)

Powder samples of the compounds (A₃N)As (A = Mg, Ca, Sr, Ba) were prepared by reacting the respective alkaline earth metal nitrides and arsenic in nickel ampoules. (Mg₃N)As crystallizes in a cubic unit cell (space group Pm3 m, no. 221) with inverse perovskite structure. The analogous compounds of calcium, strontium, and barium crystallize in an orthorhombic unit cell (space group Pnma, no. 62) as distorted inverse perovskites in the GdFeO₃ structure type. The degree of distortion was quantified based on a newly developed vectorial comparison of the atomic sites of coordination polyhedra with the ideal positions (PolyDis). Based on this analysis, the distortion increases with the size of the alkaline earth metal cation.     

Eu2+在碱土金属氟卤化物MFX(M=Ca、Sr或Ba,X=Cl、Br或I)中的发光

我们合成了六种Eu²⁺激活的碱土金属氟卤化物MFX:Eu²⁺(M=Ca、Sr或Ba;X=Cl、Br或I)。研究了它们的荧光发射光谱和激发光谱,讨论了Eu²⁺离子的跃迁发射随基质晶体组成和结构变化的规律。根据晶体场理论,按照C_4v点对称性,计算得到在MFCl:Eu²⁺(M=Ca、Sr或Ba)晶体中Eu²⁺离子的4?⁶5d¹激发态能级分裂的数值。     

Mechanochemical Synthesis and Characterization of Alkaline Earth Metal Terephthalates: M(C8H4O4)·nH2O (M = Ca,Sr, Ba)

The mechanochemical synthesis offers an easy access to obtain alkaline earth metal terephthalates M(C₈H₄O₄) · nH₂O (M = Ca, Sr, Ba). In the presented study we describe for the first time the mechanochemical synthesis of powders of Ca(C₈H₄O₄) · 3H₂O, Ca(C₈H₄O₄), Sr(C₈H₄O₄) · H₂O, and Ba(C₈H₄O₄), which so far were only synthesized as single crystals from aqueous solutions or by reactions in an autoclave. Furthermore, a new hydrate Ba(C₈H₄O₄) · 2(1.5)H₂O, not described so far in the literature, was prepared. All compounds were characterized by X‐ray powder diffraction, thermal analysis, elemental analysis, FT‐IR, and MAS NMR spectroscopic measurements.     

Extreme High-Voltage Electroconductivity of Molten KCl–MCl2 (M = Ca,Sr, Ba)

The electroconductivity of molten mixtures of calcium, strontium, and barium chlorides with potassium chloride (component concentrations 0, 25, 50, 75, 100 mol %) is studied as a function of the electric field strength. Isotherms of extreme high-voltage conductivities of the mixtures are an additive function of the composition, as opposed to isotherms of low-voltage conductivity, which exhibit considerable deviations and pass through minimums.     

ErCl3—MCln体系相图的研究

借助于DTA与X射线衍射法研究了ErCl_3-MCl_n(M=Li,Ca,Pb;n=1,2)二元体系相图.发现ErCl_3-LiCl体系相图属固液异组成型,有一固液异组成化合物Li_3ErCl_6生成,且在466℃有一相转变.其无变点分别为e 40.0mol(％)ErCl_3(479℃)和p31.0mol(％)ErCl_3(522℃);而ErCl_3-CaCl_2,PbCl_2体系皆属简单低共熔型相图.其低共熔点e分别为:46.0 mol(％)ErCl_3(578℃)和38.0mol(％)ErCl_3(405℃).ErCl_3-PbCl_2体系在固相下有一不稳定化合物PbErCl_5生成,在356℃分解.同时探讨了相图的某些规律.     

The Periodate‐Based Double Perovskites M2NaIO6 (M = Ca,Sr, and Ba)

The crystal structures of the M₂NaIO₆ series (M = Ca, Sr, Ba), prepared at 650 °C by ceramic methods, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by oxidizing I^– with O₂^(air) to I⁷⁺ followed by crystal growth in the presence of NaF as mineralizator, or by the reaction of the alkali‐metal periodate with the alkaline‐earth metal hydroxide. All three compounds are insoluble and stable in water. The barium compound crystallizes in the cubic space group Fm3m (no. 225) with lattice parameters of a = 8.3384(1) Å, whereas the strontium and calcium compounds crystallize in the monoclinic space group P2₁/c (no. 14) with a = 5.7600(1) Å, b = 5.7759(1) Å, c = 9.9742(1) Å, β = 125.362(1)° and a = 5.5376(1) Å, b = 5.7911(1) Å, c = 9.6055(1) Å, β = 124.300(1)°, respectively. The crystal structure consists of either symmetric (for Ba) or distorted (for Sr and Ca) perovskite superstructures. Ba₂NaIO₆ contains the first perfectly octahedral [IO₆]^5– unit reported. The compounds of the ortho‐periodates are stable up to 800 °C. Spectroscopic measurements as well as DFT calculations show a reasonable agreement between calculated and observed IR‐ and Raman‐active vibrations.     

Kinetics of thermal decomposition of MCO3 to MO (M=Ca,Sr and Ba)

The kinetics of the thermal decompositions of CaCO₃, SrCO₃ and BaCO₃ into their oxides were studied by thermogravimetry at constant and linearly increasing temperatures. The kinetics of the isothermal decompositions of calcium and strontium carbonates were described by the lawR _n =1–(1–)^1/n , wheren=1.8 and 1.2, respectively. The kinetics of the non-isothermal decompositions of the two carbonates, analysed by the Ozawa and Coats-Redfern methods, were in keeping with the isothermal kinetics. True kinetic compensation laws were established for each decomposition of the two carbonates, including the data under both isothermal and non-isothermal conditions.As concerns the decompositions of BaCO₃, however, there was some difference between the kinetic features relating the isothermal and non-isothermal conditions. A true kinetic compensation law was not established in this case.

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Zusammenfassung Die Kinetik der thermischen Zersetzung von CaCO₃, SrCO₃ und BaCO₃ zu den Oxiden wurden durch Thermogravimetrie bei konstanter und linear ansteigender Temperatur untersucht. Die Kinetik der isothermen Zersetzung von Calcium- und Strontium-carbonat folgt dem GesetzR _n =1–(1 –)^1/n, won=1,8 bzw. 1,2. Die Kinetik der nichtisothermen nach den Methoden von Ozawa und Coats-Redfern analysierten Zersetzung der zwei Carbonate ist in Übereinstimmung mit der isothermen Zersetzung. Wahre kinetische Kompensationsgesetze wurden für die Zersetzung der beiden Carbonate erhalten, einschließlich der sich sowohl auf isotherme als auch auf nichtisotherme Bedingungen beziehenden Daten. Was die Zersetzung von Bariumcarbonat betrifft, so wurden einige Unterschiede im kinetischen Verhalten bei der Zersetzung unter isothermen und nichtisothermen Bedingungen festgestellt. Ein wahres kinetisches Kompensationsgesetz konnte in diesem Falle nicht ermittelt werden.

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, . R _n =1–(1–)^1/n , , , 1,8 1,2. , -, . « » , . , , . - «» .

     

Optical Temperature-Sensing Performance of Nd3+:MF2 (M=Ba,Ca, Sr) Crystalline Powders Prepared by Combustion Synthesis

There is a large interest in luminescent materials for application as temperature sensors. In this scenario, we investigate the performance of neodymium-doped alkaline-earth fluoride (Nd³⁺:MF₂; M=Ba, Ca, Sr) crystalline powders prepared by combustion synthesis for optical temperature-sensing applications based on the luminescence intensity ratio (LIR) technique. We observe that the near-infrared luminescence spectral profile of Nd³⁺ changes with the temperature in a way that its behavior is suitable for optical thermometry operation within the first biological window. We also observe that the thermometric sensitivities of all studied samples change depending on the spectral integration range used in the LIR analysis. Nd³⁺:CaF₂ presents the largest sensitivity values, with a maximum absolute sensitivity of 6.5×10⁻³/K at 824 K and a relative sensitivity of 1.71 %/K at human-body temperature (310 K). The performance of CaF₂ for optical thermometry is superior to that of β-NaYF₄, a standard material commonly used for optical bioimaging and temperature sensing, and on par with the most efficient oxide nanostructured materials. The use of thermometry data to help understand structural properties via Judd-Ofelt intensity standard parameters is also discussed.     

阴极催化剂Sm1.5Sr0.5MO4 (M＝Ni, Co, Fe)在低温常压下合成氨

利用溶胶—凝胶法制备了复合氧化物Sm1.5Sr0.5MO4 (M＝Ni, Co, Fe)(SSM),并利用XRD和SEM等对样品进行表征。用Nafion膜作电解质、以SSM作为阴极、Ni-SDC金属陶瓷为阳极、银-铂网做集流体组成单电池,在温度为25℃～100℃的低温常压下以干燥氮气和湿的氢气为原料进行电化学合成氨气测定,同时研究了影响氨合成的关键因素,确定了合适的工作温度,实验结果表明,最高氨产率可达到1.05×10-8mol·s-1·cm-2。     

碱土金属钛酸盐-TiO2异质结型复合光催化活性研究

采用溶胶-凝胶法制备碱土金属钛酸盐MTiO3(M=Mg,Ca,Sr,Ba),并进一步与TiO2固相法复合制备MTiO3-TiO2异质结型复合光催化剂.以光催化降解亚甲基蓝(MB)为探针,评价了MTiO3和MTiO3-TiO2光催化剂的活性变化.结果表明,紫外光条件下碱土金属钛酸盐MTiO3的光催化活性顺序为:CaTiO3>BaTiO3>SrTiO3>MgTiO3,钙钛矿化合物的容忍因子、电负性以及催化剂的吸附性能都影响催化剂的降解效率.MTiO3与TiO2复合后形成的异质结复合光催化剂的催化活性得到显著的提高,催化剂浓度1.0g/L时,光催化反应1h后,MB(25mg/L)的降解率分别为82.6%,99.8%,93.7%,97.3%,异质结复合光催化剂活性顺序与MTiO3一致.光催化活性的提高与异质结界面形成电荷定向流动,促进光生电子、空穴的分离有关.     

新铌酸盐Ba5LnZnNb9O30(Ln=Y,La)的合成、结构与介电性能

在BaO-Ln2O3-ZnO-Nb2O5(Ln=Y,La)体系中通过固相反应法合成了填满型钨青铜结构的新铌酸盐Ba5YZnNb9O30与Ba5LaZnNb9O30.采用X射线衍射分析和扫描电镜进行了结构分析,并进行了介电性能测试.结果表明,Ba5YZnNb9O30为弛豫性铁电体,10kHz时的居里温度为25℃;室温时为四方钨青铜结构铁电相,晶胞参数a=1.25255(4)nm,c=0.39530(2)nm;1MHz时陶瓷体的室温相对介电常数为456.Ba5YZnNb9O30在室温下为四方钨青铜结构顺电相,晶胞参数a=1.25731(3)nm,c=0.39812(2)nm;频率为1MHz时,其陶瓷的室温相对介电常数为316.     

Contribution a l'etude des systemes Ca3(PO4)2-MSO4 (M=Sr,Ba)

In the systems Ca₃(PO₄)₂-MSO₄ (M = Sr, Ba), the series of single phase Ca_21?3xM_2xI(PO₄)_14?2x(SO₄)_2x with 0<x<0.15 forM=Sr and 0<x<0.1 forM = Ba have been prepared. These solid solutions, respectively strontium phosphosulfate and barium phosphosulfate, are isostructural with anhydrous tricalcium orthophosphate. They have been characterized by their infrared spectra and their crystallographic unit cell parameters.     

Ce~（3＋）在钙钛矿型KMF_3（M＝Mg、Ca、Sr、Ba）基质中的发光特性

采用高温固相反应法，在Ａｒ气氛中合成了ＫＭＦ３（Ｍ＝Ｍｇ、Ｃａ、Ｓｒ、Ｂａ）基质化合物和掺杂Ｃｅ３＋的磷光体。经Ｘ射线衍射分析确定，ＫＭｇＦ３和ＫＣａＦ３属于立方晶系、钙钛矿型结构，ＫＳｒＦ３和ＫＢａＦ３具有类似的结构。测定了ＫＭＦ３∶Ｃｅ３＋的发光光谱，观察到与其结构对应的分为二种不同的光谱结构，讨论了Ｃｅ３＋的取代格位