Solid-state cells with buffer electrodes for accurate thermodynamic measurements: system Nd-Ir-O

A new design for the solid-state cell incorporating a buffer electrode for high-temperature thermodynamic measurements is presented. The function of the buffer electrode, placed between the reference and working electrodes, is to absorb the electrochemical flux of the mobile species through the solid electrolyte caused by trace electronic conductivity. The buffer electrode prevents polarization of the measuring electrode and ensures accurate data. The application of this novel design and its advantages are demonstrated by measurement of the standard Gibbs energies of formation of Nd6Ir2O13 (low-temperature form) and Nd2Ir2O7 in the temperature range from 975 to 1450 K. Yttria-stabilized zirconia is used as the solid electrolyte and pure oxygen gas at a pressure of 0.1 MPa as the reference electrode. For the design of appropriate working electrodes, phase relations in the ternary system NdIrO were investigated at 1350 K. The two ternary oxides, Nd6Ir2O13 and Nd2Ir2O7, compositions of which fall on the join Nd2O3IrO2, were found to coexist with pure metal Ir. Therefore, two working electrodes were prepared consisting of mixtures of Ir+Nd2O3+Nd6Ir2O13 and Ir+Nd6Ir2O13+ Nd2Ir2O7. These mixtures unambiguously define unique oxygen chemical potentials under isothermal and isobaric conditions. The standard Gibbs energies of formation (ΔG°f (ox)) of the compounds from their component binary oxides Nd2O3 and IrO2, obtained from the emf of the cells, can be represented by the equations:View the MathML source View the MathML source Based on the thermodynamic information, chemical potential diagrams for the system NdIrO are developed.

Solid state electrochemical sensor for monitoring Mg in Al refining process

Novel solid-state electrochemical sensors have been designed using the Mg2+ cation conductors incorporating novel solid-state reference electrodes for in-line monitoring of Mg in molten Al during the refining process and also for in-line monitoring of Mg content in molten Al in the alloying process. In this paper we report the preparation of Mg2+ ion conductors, MgAl2O4 and MgZr4(PO4)6, by the solid state ceramic synthesis route, measurement of their electrical properties using ac-impedance spectroscopy and application of the above cation conductors for designing novel electrochemical sensors for monitoring Mg dissolved in molten Al. The activation energy for Mg2+ ion conduction in MgAl2O4 is 2.08 eV and in MgZr4(PO4)6 is 1.7 eV, respectively. The sensors have been found to respond rapidly to change in Mg content in molten aluminium around 1000 K.

Developments in solid-state under-frequency relays

Simpler circuits for frequency-sensitive relays responding to change and rate of change of system frequency have been developed employing phase-locked loops. A new relay responding to time intergral of the fall in system frequency has also been developed and its performance has been compared with those responding to change and rate of change of system frequency. The relays have been tested and calibrated with the help of a specially designed calibration kit.

PEO|Sncl(2)|PANI composites: as an electrolyte in solid-state battery

Solid-state polymer electrolytes possess high conductivity and have advantages compared with their liquid counterparts. The polyethylene oxide (PEO)-based polymer is a good candidate for this purpose. The PEO/SnCl2/polyaniline composite (PSP composites) at different weight percentages were prepared in anhydrous acetonitrile media. Structural studies were carried out of the prepared composites by X-ray diffraction, Fourier transmission infrared spectroscopy, and surface morphology by scanning electron microscopy. The sigma (dc) was carried out by a two-probe method, and it is found that the conductivity increases with an increase in temperature. The temperature-dependent conductivity of the composites exhibits a typical semi-conducting behavior and hence can be explained by the 1D variable range hopping model proposed by Mott. The electrochemical cell parameters for battery applications at room temperature have also been determined. The samples are fabricated for battery application in the configuration of Na: (PSP): (I-2 + C + sample), and their experimental data are measured using Wagner's polarization technique. The cell parameters result in an open-circuit voltage of 0.83 V and a short-circuit current of 912 mu A for PSP (70:30:10) composite. Hence, these composites can be used in polymer electrolyte studies.

Solid State and Solution Mediated Multistep Sequential Transformations in Metal-Organic Coordination Networks

Sequential transformation in a family of metal-organic framework compounds has been investigated employing both a solid-state as well as a solution mediated route. The compounds, cobalt oxy-bis(benzoate) and manganese oxybis(benzoate) having a two-dimensional structure, were reacted with bipyridine forming cobalt oxy-bis(benzoate)-4,4'-bipyridine and manganese oxy-bis(benzoate)-4,4'-bipyridine, respectively. The bipyridine containing compounds appear to form sequentially through stable intermediates. For the cobalt system, the transformation from a two-dimensional compound, Co(H2O)(2)(OBA)] (OBA = 4,4'-oxy-bis(benzoate)), I, to two different three-dimensional compounds, Co(bpy)(OBA)]center dot bpy, II, (bpy = 4,4'-bipyridine) and Co(bpy)(0.5)(OBA)], III, and reversibility between II and III have been investigated. In the manganese system, transformation from a two-dimensional compound, Mn(H2O)(2)(OBA)], Ia, to two different three-dimensional compounds, Mn (bpy)(OBA)]center dot bpy, Ha and Ha to Mn(bpy)(0.5)(OBA)], Ilia, has been investigated. It has also been possible to identify intermediate products during these transformation reactions. The possible pathways for the formation of the compounds were postulated.

The Relationship of Solid-State Plasticity to Mechanochromic Luminescence in Difluoroboron Avobenzone Polymorphs

In solid-state mechanochromic luminescence (ML) materials, it remains a challenge to establish the origin of fluorescence color changes upon mechanical action and to determine why only some fluorophores exhibit ML behavior. The study of mechanical properties by nanoindentation, followed by ML experiments on green- and cyan-emitting polymorphs of difluoroboron avobenzone reveals that upon smearing, the plastically deformable cyan form shows a prominent color change to yellow, while in the harder green form the redshifted emission is barely detectable. Crystal structure analysis reveals the presence of slip planes in the softer cyan form that can facilitate the formation of recoverable and low energy defects in the structure. Hence, the cyan form exhibits prominent and reversible ML behavior. This suggests a potential design strategy for efficient ML materials.

Diaminotriazine substituted diphenyl ether: reversible structural transformation and solvent dependent solid state fluorescence

The effect of molecular shape and position of hydrogen bonding functionality in the solid state structural self-assembly was investigated using diaminotriazine substituted diphenyl ether based positional isomers (1-5). The molecular shape was modulated by changing diaminotriazine position that produced channel supramolecular structures in 1, 3 and 5. There exists a direct correlation between the molecular shape and three dimensional structures; more linear molecules resulted in close-packing whereas molecules with a labyrinthine topology formed a channel structure. Supramolecular aspects pertaining to the influence of solvent of crystallization in structure formation and reversible structural transformation in solid state were also explored. 1-5 exhibited tunable solid state fluorescence (lambda(max) = 437-496 nm) depending on the diaminotriazine substitutional position and 3 showed solvent-dependent solid state fluorescence. The present study describes the generation of a supramolecular channel structure with functional properties such as tunable fluorescence by varying the position of hydrogen bond functionality and solvent of crystallization.

Revisiting borylanilines: unique solid-state structures and insight into photophysical properties

The structure and photophysical properties of two known borylanilines, 4-(dimesitylboryl)aniline (1) and 4-(dimesitylboryl)-3,5-dimethylaniline (2), have been investigated. 1 and 2 have similar donor and acceptor centers but differ in their molecular conformations. Compounds 1 and 2 have been structurally characterized, and they exhibit a rare form of intermolecular N-H - - -pi electrostatic interactions. The structure and photophysical properties of 1 and 2 are discussed in the context of computational results.

A new 3D cadmium(II) coordination polymer having mu(4)-oxalato, mu-aquo and mu-chlorido bridges: crystal structure, solid state fluorescence and thermal behavior

A new 3D cadmium(II) coordination polymer, Cd(C2O4)(0.5)Cl(H2O)](n) (1) has been synthesized from a mixture of CdCl2. H2O and (NH4)(2)C2O4 in a slightly acidic pH. Its molecular structure was determined by single crystal X-ray diffraction which reveals that the new polymeric structure consists of simultaneous mu(4)-oxalato, mu-aquo, and mu-chlorido bridges between the metal centers, embedded in distorted pentagonal bipyramidal geometries. On thermal analysis compound exhibits high thermal stability up to 330 degrees C. Compound 1 also exhibits strong fluorescent emission. (c) 2013 Elsevier B.V. All rights reserved.

Experimental evidence for `carbon bonding' in the solid state from charge density analysis

The validity of the newly proposed `carbon bonding', an interaction where a carbon atom acts as an electrophilic site towards a variety of nucleophiles, has been investigated in the solid state. X-ray charge density analysis provides experimental evidence for this hitherto unexplored interaction and unravels its nature and strength.

Photophysical, electrochemical and solid state properties of diketopyrrolopyrrole based molecular materials: importance of the donor group

Diketopyrrolopyrrole (DPP) based molecular semiconductors have emerged as promising materials for high performance active layers in organic solar cells. It is imperative to comprehend the origin of such a property by investigating the fundamental structure property correlation. In this report we have investigated the role of the donor group in DPP based donor-acceptor- donor (D-A-D) structure to govern the solid state, photophysical and electrochemical properties. We have prepared three derivatives of DPP with varying strengths of the donor groups, such as phenyl (PDPP-Hex), thiophene (TDPP-Hex) and selenophene (SeDPP-Hex). The influence of the donor units on the solid state packing was studied by single crystal X-ray diffraction. The photophysical, electrochemical and density functional theory ( DFT) results were combined to elucidate the structural and electronic properties of three DPP derivatives. We found that these DPP derivatives crystallized in the monoclinic space group P21/c and show herringbone packing in the crystal lattice. The derivatives exhibit weak p-p stacking interactions as two neighboring molecules slip away from each other with varied torsional angles at the donor units. The high torsional angle of 32 degrees ( PDPP-Hex) between the phenyl and lactam ring results in weak intramolecular interactions between the donor and acceptor, while TDPP-Hex and SeDPP-Hex show lower torsional angles of 9 degrees and 12 degrees with a strong overlap between the donor and acceptor units. The photophysical properties reveal that PDPP-Hex exhibits a high Stokes shift of 0.32 eV and SeDPP- Hex shows a high molar absorption co-efficient of 33 600 L mol -1 1 cm -1 1 with a low band gap of similar to 2.2 eV. The electrochemical studies of SeDPP- Hex indicate the pronounced effect of selenium in stabilizing the LUMO energy levels and this further emphasizes the importance of chalcogens in developing new n-type organic semiconductors for optoelectronic devices.

Symbiosis in Solid State Interconversion and Synthon Modularity in Hydroxybenzoic Acid-Hexamine Adducts

Systematic cocrystallization of hydroxybenzoic acids with hexamine using liquid-assisted grinding shows facile solid state interconversion among different stoichiometric variants. The reversible interconversion caused by varying both the acid and base components in tandem is shown to be a consequence of hydrogen-bonded synthon modularity present in all representative crystal structures. Among a total of 11 complexes, three are salts and eight are cocrystals. The insulated synthons appear as conserved tetrameric motifs in the structures, and the mechanism of interconversion is closely monitored by the synthon modularity. The interconversion is consistent with the theoretically computed stabilization energies of all the tetramers found in this series of cocrystals based on atoms in molecule calculations.