Structure Of Intermediate Phase Research Articles

Effect of Chloride Incorporation on the Intermediate Phase and Film Morphology of Methylammonium Lead Halide Perovskites.

The influence of chloride integration on perovskite film deposition, encompassing both the structures of intermediate phases and the properties of the final films, was explored. Our methodology involved the fabrication of perovskite intermediate-phase films with varying concentrations of methylammonium chloride (MACl). Subsequently, we conducted an analysis employing X-ray diffraction and Rietveld refinement, incorporating the March-Dollase correction, to gain insights into how chloride-induced intermediate phases impact film morphology. Remarkably, a distinct preferred orientation was observed in the (020) lattice plane perpendicular to the substrate surface, and this orientation was found to be directly correlated to the MACl concentration. This distinctive arrangement of chloride-induced intermediate-phase complexes facilitated controlled crystallization, leading to highly oriented crystals and an improved film morphology. As a consequence, perovskite solar cell devices incorporating chloride-containing methylammonium lead iodide achieved a power conversion efficiency exceeding 20%. These findings suggest a crucial link between the preferred orientation observed in the final chlorine-derived perovskite films and the intermediate-phase structure formed during the initial stages of perovskite formation. These results suggest a profound impact of intermediate phase compositions and crystal structures on perovskite formation, emphasizing the importance of a comprehensive understanding of these factors to enable precise control over ideal structures and the subsequent transformation into high-quality perovskite films.

Changes in the structures of mixed-layer illite-smectite during flooding of terrigenous oil reservoirs

A difference-spectrum method is proposed for the qualitative assessment of changes of illite-smectite structures accompanying the flooding of oil reservoirs. The method permits one to get an open system and reduce the application of procedures based on Markov’s chain formalism. A computer simulation is made to obtain spectra by subtracting the spectrum of an ethylene glycol-saturated sample from the spectrum of an air-dried preparation throughout the entire range of concentrations of illite and smectite components with a short-range order factor R = 0 or R = 3.It has been established that only in the presence of filtration are the maximum and minimum of the spectra in the range of 12.5-9.4 A complicated by a number of local extrema, whose position is specified by the structure of intermediate phases. The flooding process first involves mixed-layer phases with R = 0, leading to a partial segregation of the structures into phase with one and two networks of interlayer H2O. When the secondary mica particles break, phases with R = 3 appear along the boundaries of nanoblocks, first only with 1 H2O and then only with 2 H2O in labile interspaces. Their coexistence with the phases R = 0 in the sample proves the existence of percolation effects due to two-phase filtration in the porous medium. The fully flooded reservoir is always dominated by a mechanical mixture of illite-smectite phases of different nature with R = 0 and with different ratios of components. Transformation of mica that can drastically reduce oil production begins long before the appearance of flooding zones, which are revealed by standard logging methods.

Model‐independent structure and resonant X‐ray spectra of intermediate smectic phases

It is shown that the orientational structure of intermediate smectic phases can be determined using the symmetry properties of the general free energy with arbitrary orientational coupling between smectic layers, without addressing a particular model. The structure of three‐ and four‐layer intermediate phases, obtained in this way, corresponds to experimental data. The same method enables one to predict the structure of intermediate phases with periodicity of five and six layers, which have not been observed experimentally so far. The resonant X‐ray spectra of the five‐ and six‐layer intermediate phases with predicted structure have also been calculated. These spectra are characterized by a number of features which enable one to distinguish five‐layer and six‐layer intermediate phases from phases with smaller periods.

Theoretical Studies of the Structure of Intermediate Chiral Smectic Phases with Increasing Periodicity

Different approaches to the description of the structure of intermediate chiral smectic C* phases are discussed and the concept of the “discrete” flexoelectric effect is introduced that describes a polarization induced in a smectic layer by a difference in director orientation in the two other layers adjacent to it. It is shown that the “discrete” flexoelectric effect is determined by electrostatic dipole-quadrupole interaction between positionally correlated molecules located in adjacent smectic layers. It is also shown that a simple discrete model proposed in the literature can be used to describe the whole sequence of intermediate chiral smectic C* phases with increasing periods, and to determine the non-planar structure of each phase without additional assumptions. In this sequence the phases with three and four layer periodicity have the same structure, as observed in the experiment. The theory predicts also the structure of intermediate phases with longer periods that have not been studied experimentally so far. The influence of long-range interaction between polarization fluctuations in different layers, proposed by Prost and Bruinsma, is also considered. Several intermediate phases are shown to be suppressed by this interaction, while the stability of the phases three and four layer periodicity is increased.

A study of high-temperature precipitation in Al–Mg–Si alloys with an excess of silicon

The high-temperature decomposition phenomena were examined for two Al–Mg–Si alloys with an excess of silicon. The kinetics of precipitation were studied by transmission electron microscopy and by measurement of the thermoelectric power in the temperature range from 300 to 525 °C. It was shown that decomposition occurs either at 300–400 °C by the precipitation of intermediate β′ phase (different structures are possible depending on the alloy), which is then gradually replaced by the equilibrium β phase or, between 400 and 500 °C, by direct precipitation of the β phase from the supersaturated solid solution. The precipitation of silicon was also observed. At 300–350 °C, a near equilibrium in composition solid solution can coexist with Mg2Si phases out of equilibrium. Structures of intermediate phases and their orientation relationships with the matrix are given. The diagram of isothermal precipitation is constructed as an S-curve.

Crystal Structure of Intermediate Phases in Binary B-Metal Alloys Induced by High Pressure

Crystal Structure of Intermediate Phases in Binary B-Metal Alloys Induced by High Pressure

Structures related to those of spinel and theβ-phase, and a possible mechanism for the transformation olivine ↔ spinel

The structures of intermediate phases, such as the β -phase, are shown to be readily derived from that of spinel ( γ ) by the regular insertion of anti-phase boundaries ( apbs ) or mirror planes parallel to (010) of the body-centered tetragonal unit cell of the latter [[unk]10) planes of the face-centred cubic cell]. The process leads eventually to a hypothetical structure, ω , from which γ , β , etc. can be derived by similar apbs . Unit layers parallel to (0[unk]2) in the ω structure are identical to those parallel to (001) in olivine ( α , setting Pnma ). A simple mechanism is proposed for the transformation α ↔ ω . Further transformation to β etc. and γ requires only slip, to generate apbs .

Effects of Carbon Content on the Structure of Intermediate Phase in TiC-Ni-Mo alloys

Changes in various properties of TiC-Ni-Mo alloys during sintering process were observed to study the effect of carbon content on the structure of intermediate phase formed around the TiC grain. The results are as follows.(1) The wetting of TiC by Ni-Mo alloy were improved by increasing carbon content.(2) With an increase in the carbon content, the carbide grains changed from angular to spherical forms. The grain size and the thickness of the intermediate phase of carbide were reduced.(3) The structure of the intermediate phase were examined by X-ray microanalyser as follows. These results were demonstrated clearly by the presence of a molybdenum-rich zone at the edge of carbide coupled with a molybdenum-free region in the core of grains.As the carbon content in TiC-Ni-Mo alloys increases, this molybdenum-rich zone was found to approach the core boundary, and the diffusion of nickel from the liquid nickel into the intermediate phase and the solution of carbide into the nickel binder were reduced.

Borides and silicides of the platinum metals.

LITTLE attention has hitherto been given to the composition and structure of intermediate phases in the twelve binary systems comprising boron or silicon with ruthenium, rhodium, palladium, osmium, iridium or platinum. Each of the twelve systems has now been studied over the full range of composition, and the phases listed in the accompanying table have been characterized.