Alkali Metal Azides Research Articles

A New and Simple Route to Alkali Metal Oxometalates

Highly reactive alkali metal oxides are generated in situ from alkali metal azides. Their reaction to give ternary oxides, however, proceeds in a controlled manner, and thus provides an elegant synthesis route to alkali metal oxometalates.

Superconductivity of Alkali Metal Intercalated Niobate with a Layered Perovskite Structure

Alkali metal intercalated compounds of a layer structured perovskite, KCa2Nb3O10, have been prepared by the reaction with n-butyllithium or alkali metal azides, AN3 (A = Li and Na). The magnetic susceptibility measurements showed that the compounds became superconductors with transition temperatures ranging from 3 - 6 K.

Electronic Structure of Metal Azides

AbstractCalculations of energy band structure, density of states, electronic density, and chemical bond parameters for a series of MeN3, where Me  Na, K, Rb, Cs, Ag, Tl have been given. The density functional theory and pseudopotential technique in mixed basis have been used. The valence band has been shown to be essentially formed from azideion states for alkali metal azides. The conduction band contains two subbands separated by a band gap. The first band is responsible for the anion states, while the second one is responsible for the cation ones. Silver d‐states and thallium s‐states have been seen to change greatly the structure of both the valence and conduction bands for AgN3 and TlN3, viz. the upper valence bands are of a mixed anion‐cation nature, the conduction band bottom consists of cation states, but the anion contributions increase when the energy grows.

Thermal behavior of alkali metal azides in NaY-FAU zeolite

The thermal behavior of pure alkali metal azides and their mechanical mixtures with NaY-FAU zeolite was investigated by means of thermogravimetry and IR spectroscopy. LiN3, KN3, RbN3 and CsN3 were prepared from NaN3 by ion-exchange. The pure azides exhibited low thermal stability, hindering the precise spectroscopic characterization in some cases. The decomposition of each azide in the zeolite took place above the temperature characteristic for the pure azide, demonstrating the stabilization of the azide in the zeolite cavities. This feature was the only common characteristic established for the azide/zeolite systems.

Banding and electronic structures of metal azides——Sensitivity and conductivity

By using both DV-Xα and EH-CO methods, the calculation studies of the structure-property relationships of a series of metal azides, of their clusters' electronic structures in ground and excited states, of their systems with cation vacancy and the doped Pb(N3)2, as well as their crystal band structures have been conducted. The results show that the sensitivity of ionic-type metal azides varies with the degree of difficulty of electronic transition of the losing charge on N3. A metal azide with cation vacancies has a greater sensitivity than the perfect one. When doped with monovalent metal ions, lead azide's sensitivity increased; when with trivalent ones, its sensitivity decreased; when with divalent ones, little of it changed. Compared with heavy metal azides. an alkali metal azide has a larger band gap, a smaller band width and a greater transition energy of frontier electron with a smaller amount of losing charge on N3, and thus has lower sensitivity and conductivity than heavy metal azides.

A Study on Sensitivity and Conductivity of Alkali and Heavy Metal Azides

A Study on Sensitivity and Conductivity of Alkali and Heavy Metal Azides

Superconductivity and Site-Selective Intercalation in KRbCsC60

Ternary-alkali-metal-intercalated fullerides, KRbCsC 60 , was prepared by method employing alkali metal azides reported by Bensebaa et al . (F. Bensebaa, B. Xiang and L. Kevan: J. Phys. Chem. 96 (1992) 6118). We found that KRbCsC 60 is a superconductor with the transitipn temperature of 28(bulk)∼29 K (onset). It was also found, from nuclear magnetic resonance (NMR) study of 87 Rb and 133 Cs in this system, that the alkali atoms are site-selectively intercalated into C 60 face-centered-cubic (fcc) lattice. The largest alkali-metal ion, Cs, occupies octahedral sites of the C 60 fcc lattice, and the K and Rb atoms occupy mainly tetrahedral sites.

A model for rubidium diffusion in RbxC60 fullerites

Superconducting fullerite Rb[sub 3]C[sub 60] synthesized using alkali-metal azides as a source of the alkali metal shows time-dependent development of the superconducting phase based on electron spin resonance and low-field microwave absorption data. Time dependences of both signals observed for several hours after the synthesis are described by the Avrami diffusion model assuming the diffusion process Rb + C[sub 60] [yields] Rb[sub 3]C[sub 60]. The model permits calculation of the Josephson penetration depth as [lambda][sub J] [approximately] 1500 Angstroms, which is in agreement with other measurements. 18 refs., 2 figs.

Thermochemistry of the azide anion: assignment of .DELTA.fH0(N3-,g) using viscosity B-coefficient data

Uncertainty concerning the magnitudes of key thermodynamic values at the heart of azide chemistry has prevailed for a number of years. The «direct» experimental determination of quantities like Δ f H 0 (N 3 - ,g), differ quite markedly (some 50 kJ mol -1 ) from the values indicated from indirect thermochemical cycles via lattice energies. The viscosity B-coefficients of alkali metal azides in aqueous solution are utilised, in conjunction with a well-established correlation, to estimate these important quantities from a new standpoint

Einkristallzüchtung und Strukturverfeinerung von KAu 5 und RbAu 5

Green gleaming brittle single crystals of KAu 5 and RbAu 5 were obtained by the reaction of the alkalimetal azides with gold powder at 700 °C. The structures were determined from single-crystal diffractometer data: space group P6/ mmm, Z = 1; KAu 5, a = 5.663(1) A ̊ , c = 4.483(1) A ̊ , R/R w (w = 1) = 0.036/0.041, N( F o 2) ⩾ 3 σ(F o 2) = 234 and N(var.) = 9; RbAu 5, a = 5.762(2) A ̊ , c = 4.442(2) A ̊ , R/R w (w = 1) = 0.048/0.073, N( F o 2) ⩾ 3 σ(F o 2) = 248 and N(var.) = 9. Both compounds crystallize in the CaCu 5-structure type with negligible deviation from the ideal 1:5 composition.

Electron spin resonance and low-field microwave absorption of alkali-metal-doped fullerene C60 superconductors

Alkali-metal-doped C[sub 60] superconductors formed by alkali-metal azide decomposition show a time evolution for the development of the superconducting phase after initial sample preparation which extends over about 15 h for storage at room temperature. This is studied quantitatively for K[sub 3]C[sub 60] and Rb[sub 3]C[sub 60], and differences are seen between these two systems which are consistent with redistribution of the alkali metal in the C[sub 60] matrix accounting for the time evolution observed. This is supported by separate experiments in which the storage temperature after sample preparation is decreased to 77 K. It is interesting that electron spin resonance (ESR) signals are seen in all of these samples in both the superconducting and nonsuperconducting temperature regions and that they show time evolutions after sample preparation that are qualitatively similar to the low-field microwave absorption (LFMA) signals which characterize the development of the superconducting phase. However, a detailed comparison shows differences between the ESR signal changes with time and the development of the superconducting phase which suggests that the origins of the ESR and LFMA signals are independent. It is interesting that similar ESR changes with storage time are observed in nonsuperconducting Cs[sub 3]C[sub 60] as are observed inmore » superconducting K[sub 3]C[sub 60] and Rb[sub 3]C[sub 60]. 10 refs., 10 figs.« less

A new preparation method for superconducting alkali-metal-doped fullerenes: comparison of ac susceptibility and low-field microwave absorption characterization

Alkali-metal-doped fullerenes are prepared by a rapid, new method employing alkali-metal azides. By means of ac susceptibility and low-field microwave absorption (LFMA), the authors have investigated the superconducting phases in K- and Rb-doped C. With Rb doping, the transition to the superconducting state takes place at T{sub c} = 38 K when observed by LFMA. The LFMA signal shows significant hysteresis behavior. During a day following the doping process, the LFMA for nominal composition Rb{sub 3}C{sub 60} is found to be drastically time dependent. Measurements by ac susceptibility, on the same sample, show an onset at 34 K which is lower than the T{sub c} obtained by LFMA but higher than the highest value reported for Rb{sub 3}C{sub 60} by ac susceptibility. This could indicate the presence of another superconducting phase. At 12 K the superconducting fraction is found to be about 95% by ac susceptibility so the material formed by this new preparation method is almost entirely superconducting. 22 refs., 4 figs., 1 tab.

Formation of alkali metal particles in alkali metal cation exchanged X zeolite exposed to alkali metal vapor: control of metal particle identity

The serie of five alkali metal (M 2 ) vapors formed by alkali metal azide decomposition were reacted with the series of alkali metal (M 1 ) cation exchanged X zeolites to form alkali metal particles. For Rb + and Cs + exchanged X zeolites, Rb n and Cs n metal particles are formed regardless of the choice of M 2 vapor, so the cluster atoms must originate from the exchanged cations rather than the alkali metal vapor atom

Hydrogen azide-amine systems as an azide nucleophile for substitutions of sulfonates, halides, and vicinal disulfonates

Hydrogen azide-alkylamine combination turned out to ensure the displacement of simple primary or secondary sulfonates, halides, and vicinal disulfonates with an azido-group in which an enhanced reactivity is generally achieved as compared with a case of traditional alkali metal azides.

Electron paramagnetic resonance studies of the formation of alkali-metal particles and ionic clusters in alkali-metal-loaded X zeolites

Alkali metals (Li, Na, K, Rb, Cs) are loaded into the corresponding alkali-metal cation-exchanged X zeolites by alkali-metal vapour exposure and by decomposition of the corresponding alkali-metal azide mixed with the zeolite. Electron paramagnetic resonance shows that alkali-metal ionic clusters are formed, with K2+3 ionic clusters being reported for the first time in the potassium cation-exchanged X zeolites. Analysis shows that the number of nuclei in the alkali-metal ionic cluster is determined by the distribution of cations in the β-cage of the zeolite structure. Alkali-metal particles are also formed by both methods and are characterized by electron paramagnetic resonance.

Hindered rotational energy levels of linear ions in trigonal and tetragonal crystalline fields

The hindered rotational energy levels of linear ions in crystalline fields of trigonal and tetragonal symmetry have been computed. For a trigonal crystalline field, D3d symmetry, and a tetragonal crystalline field, D2h symmetry, the J = 2 and J = 4 terms have been included in the potential function. The theory of a linear ion in a trigonal field is applied to the hindered rotation of the hydrosulfide ion in the alkali metal hydrosulfides. The librational frequencies of the alkali metal azides KHF2 and TlN3 are analyzed using the model of a linear ion in a tetragonal crystalline field.

Reactions of alkali-metal azides with some organophosphorus(V) compounds

The reactions of Li[N3] or Na[N3] with some organophosphorus(V) compounds containing chloro-groups, including PCl5(py)(py = pyridine) and catechyl derivatives of PCl5, have been investigated by 31P n.m.r. spectroscopy. Several new azido-species have been identified in solution. In the PCl5(py) system, where isomerism is possible, configurations have been assigned by the method of pairwise interactions.

Reactions of alkali-metal azides with some halogenophosphorus compounds

The reactions of Li[N3] or Na[N3] with some organophosphorus(V) compounds containing chloro-groups, including PCl5(py)(py = pyridine) and catechyl derivatives of PCl5, have been investigated by 31P n.m.r. spectroscopy. Several new azido-species have been identified in solution. In the PCl5(py) system, where isomerism is possible, configurations have been assigned by the method of pairwise interactions.

Thermophysics of alkali and related azides II. Heat capacities of potassium, rubidium, cesium, and thallium azides from 5 to 350 K

The heat capacities of potassium, rubidium, cesium, and thallium azides were determined from 5 to 350 K by adiabatic calorimetry. Although the alkali-metal azides studied in this work exhibited no thermal anomalies over the temperature range studied, thallium azide has a bifurcated anomaly with two maxima at (233.0±0.1) K and (242.04±0.02) K. The associated excess entropy was 0.90 cal th K −1 mol −1. The thermal properties of the azides and the corresponding structurally similar hydrogen difluorides are nearly identical. Both have linear symmetrical anions. However, thallium azide shows a solid-solid phase transition not exhibited by thallium hydrogen difluoride. At 298.15 K the values of C p o, S o, and −{G o (T)−H o (0)} T , respectively, are 18.38, 24.86, and 12.676 cal th K −1 mol −1 for potassium azide; 19.09, 28.78, and 15.58 cal th K −1 mol −1 for rubidium azide; 19.89, 32.11, and 18.17 cal th K −1 mol −1 for cesium azide; and 19.26, 32.09, and 18.69 cal th K −1 mol −1 for thallium azide. Heat capacities at constant volume for KN 3 were deduced from infrared and Raman data.

Unstable intermediates. Part 111.—Electron spin resonance studies of γ-irradiated frozen aqueous solutions of alkali-metal azides

Aqueous glasses containing potassium or sodium azide at 77 K after exposure to 60Co γ-rays, had e.s.r. spectra containing features characteristic of NH2 radicals. Exposure to 2537 A light also gave NH2 radicals together with an isotropic 5 G triplet characteristic of nitrogen atoms. The NH2 radicals are probably formed from N2–3 or HN–3 by loss of nitrogen molecules and protonation of NH–. This occurs even in glasses containing 10 M alkali hydroxide.