IR Modes Research Articles

Vibrational, optical, electronic and electrocatalytic properties of SrCuSi4O10 ceramic

This research reports the synthesis of powdered SrCuSi4O10 ceramic powder, obtained through a solid-state chemical reaction methodology. The sample was characterized using X-ray powder diffraction (XRPD), Raman and Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), reflectance (R), electron paramagnetic resonance spectrum (EPR), lattice dynamic calculations, electronic and electrocatalytic properties analyses. The X-ray analysis showed that crystalline structure of SrCuSi4O10 compound belongs to a tetragonal system with the P4/ncc space group, containing four formulas per unit cell (Z = 4). The SEM micrographs present a morphology of layered microplates with some irregularity in size and shapes. UV–vis diffuse reflectance spectra show three intense reflection regions. Regarding the vibrational properties, the theoretical calculation was performed using a rigid ion model in order to assign the experimental Raman and IR modes. Additionally, electronic properties calculations were carried out using Density Functional Theory (DFT). Finally, the hydrogen evolution reaction (HER) performance of the SrCuSi4O10 electrocatalyst was evaluated.

Structural, optical, magnetic, and photocatalytic analysis of exclusive metal aluminates against Congo Red dye under UV light

The exclusive ZnAl2O4 (ZAO), CaAl2O4 (CAO), and MgAl2O4 (MAO) nanocrystallites were prepared by the citrate sol–gel route and further annealed at 600 °C for 2 h. XRD and Rietveld refinement were conducted to explore the crystal structure and to optimize the profile parameters. FTIR confirmed the vibrational peaks of relevant functional groups. The additional stretching and bending IR modes in MAO sample emphasized structural disorders like antisites/native defects. The UV-DRS spectra of these samples analyzed the direct bandgap in 2.76–4.29 eV range. HR-TEM micrographs characterize the well-developed nanosized grains. From VSM data, several magnetic parameters were collected for prepared aluminates and found MAO as best ferromagnetic material with the highest coercive field value (1235 Oe). PL spectra of metal aluminates suggest that the broad peak in violet-blue is attributed to the band edge emission, and finite peaks in higher wavelength regions have appeared due to the large density of surface traps and oxygen vacancies. The photocatalytic mechanism of ZAO, MAO & CAO nanopowder was elucidated on the Congo Red dye (10–70 ppm) solution after exposure to UV light. The highest value of rate constant (k = 0.0118 min−1) suggests that the MAO (0.3 g l−1) sample would be an efficient photocatalyst (98%) under UV light owing to its large surface area (125 m2 g−1) and suitable bandgap. The overall results advocate the practical applicability of aluminate photocatalysts in water treatment, spintronics, and photonics.

Syntheses and Patterns of Changes in Structural Parameters of the New Quaternary Tellurides EuRECuTe3 (RE = Ho, Tm, and Sc): Experiment and Theory.

The layered orthorhombic quaternary tellurides EuRECuTe3 (RE = Ho, Tm, Sc) with Cmcm symmetry were first synthesized. Single crystals of the compounds up to 500 μm in size were obtained by the halide-flux method at 1120 K from elements taken in a ratio of Eu/RE/Cu/Te = 1:1:1:3. In the series of compounds, the changes in lattice parameters were in the ranges a = 4.3129(3)-4.2341(3) Å, b = 14.3150(9)-14.1562(9) Å, c = 11.2312(7)-10.8698(7) Å, V = 693.40(8)-651.52(7) Å3. In the structures, the cations Eu2+, RE3+ (RE = Ho, Tm, Sc), and Cu+ occupied independent crystallographic positions. The structures were built with distorted copper tetrahedra forming infinite chains [CuTe4]7- and octahedra [RETe6]9- forming two-dimensional layers along the a-axis. These coordination polyhedra formed parallel two-dimensional layers CuRETe32-∞2. Between the layers, along the a-axis, chains of europium trigonal prisms [EuTe6]10- were located. Regularities in the variation of structural parameters and the degree of distortion of coordination polyhedra depending on the ionic radius of the rare-earth metal in the compounds EuRECuCh3 (RE = Ho, Er, Tm, Lu, Sc; Ch = S, Se, Te) were established. It is shown that with a decrease in the ionic radius ri(RE3+) in the compounds EuRECuTe3, the unit-cell volume, bond length d(RE-Te), distortion degree [CuTe4]7-, and crystallographic compression of layers [RECuTe3]2- decreased. The distortion degree of tetrahedral polyhedra [CuCh4]7-, as well as the structural parameters in europium rare-earth copper tellurides EuRECuTe3, were higher than in isostructural quaternary chalcogenides. Ab initio calculations of the crystalline structure, phonon spectrum, and elastic properties of compounds EuRECuTe3 (RE = Ho, Tm, and Sc) ere conducted. The types and wave numbers of fundamental modes were determined, and the involvement of ions in IR and Raman modes was assessed. The calculated data of the crystal structure correlated well with the experimental results.

Synthesis, Crystal Structure, and Optical and Magnetic Properties of the New Quaternary Erbium Telluride EuErCuTe3: Experiment and Calculation.

This paper reports for the first time on a new layered magnetic heterometallic erbium telluride EuErCuTe3. Single crystals of the compound were obtained from the elements at 1120 K using CsI as a flux. The crystal structure of EuErCuTe3 was solved in the space group Cmcm (a = 4.3086(3) Å, b = 14.3093(9) Å, and c = 11.1957(7) Å) with the KZrCuS3 structure type. In the orthorhombic structure of erbium telluride, distorted octahedra ([ErTe6]9-) form two-dimensional layers (Er(Te1)2/2e(Te2)4/2k-)∞2, while distorted tetrahedra ([CuTe4]7-) form one-dimensionally connected substructures (Cu(Te1)2/2e(Te2)2/1t5-∞1) along the [100] direction. The distorted octahedra and tetrahedra form parallel two-dimensional layers (CuErTe32-∞2) between which Eu2+ ions are located in a trigonal-prismatic coordination environment (EuTe610-). The trigonal prisms are connected by faces, forming chains (Eu(Te1)2/2(Te2)4/22-∞1) along the [100] direction. Regularities in the variations in structural parameters were established in the series of erbium chalcogenides (EuErCuCh3 with Ch = S, Se, and Te) and tellurides (EuLnCuTe3 with Ln = Gd, Er, and Lu). Ab-initio calculations of the crystal structure, phonon spectrum, and elastic properties of the compound EuErCuTe3 were performed. The types and wavenumbers of fundamental modes were determined, and the involvement of ions in the IR and Raman modes was assessed. The experimental Raman spectra were interpreted. The telluride EuErCuTe3 at temperatures below 4.2 K was ferrimagnetic, as were the sulfide and selenide derivatives (EuErCuCh3 with Ch = S and Se). Its experimental magnetic characteristics were close to the calculated ones. The decrease in the magnetic phase transition temperature in the series of the erbium chalcogenides was discovered.

Precursor influence on the raman spectrum of KNNLiTaLa0.01 prepared by two different methods

This work presents a study of ceramics with the (K0.44Na0.52Li0.04)0.97La0.01Nb0.9Ta0.1O3 composition through their Raman spectra. In the previous studies [1], this particular composition has shown good permittivity and piezoelectric parameter values that justify a deeper investigation. Two sets of samples of these ceramic compounds were prepared using different methods. The first set was prepared using a classical solid-state reaction of oxides and carbonates, as described in Ref. 2. The second set was prepared using the NaNbO3 as a precursor. The Raman spectra of the samples obtained by the direct ceramic method consisted of 4 modes. In contrast, the spectra of the samples obtained using the precursor showed a shift of the wavenumber of the A1g(ν1) mode peak towards lower values and consisted of six modes with the appearance of two additional IR modes, F1u(ν3) and F2g(ν4). Notably, the use of the precursor preparation route led to important improvements resulting in a more straightforward method than that of Saito et al. [3].

Calculating high-pressure vibrational frequencies analytically with the extended hydrostatic compression force field approach.

We report the implementation of the analytical Hessian for the mechanochemical extended hydrostatic compression force field method in the Q-Chem program package. To verify the implementation, the analytical Hessian was compared with finite difference calculations. In addition, we calculated the pressure dependency of the Raman active vibrational modes of methane, ethane, and hydrogen, as well as all IR and Raman active modes of Buckminsterfullerene, and compared the results with experimental and theoretical data. Our implementation paves the way for the analysis of geometric points on a pressure-deformed potential energy surface and provides a straightforward model to calculate the vibrational properties of molecules under high pressure.

Elucidating the role of oxygen vacancies on the electrical conductivity of β-Ga2O3 single-crystals

The contribution of oxygen vacancies (VO) to the electrical conductivity of unintentionally doped β-Ga2O3 has been a topic of recent debate. Here, we use a combination of Hall measurements and Raman spectroscopy on as-grown and O2-annealed β-Ga2O3 crystals to investigate the role of VO on electrical conductivity. The annealed samples show a significant decrease in carrier concentration. By comparing the relative Raman shift of individual modes with theoretically calculated contributions of oxygen sites to these modes, we verify the marked reduction of VO in annealed β-Ga2O3 crystals. Furthermore, the IR modes in β-Ga2O3, usually hidden by free carrier absorption, are clearly seen in the annealed sample. The reduction of band tail states as well as free carrier absorption in the annealed samples provides additional evidence for reduced carrier concentration related to VO, making them a key determinant of electrical conductivity in β-Ga2O3.

In situ synthesis of PuCl3 and corresponding Raman and density functional theory vibrational modes

AbstractThe experimental and calculated Raman spectrum of PuCl3 has been reported for the first time. PuCl3 is a primary species found in plutonium metal refinement, specifically in pyrochemical salt processes including multicycle direct oxide reduction, metal chlorination, and electrorefining. As such, Raman signatures of PuCl3 could serve as potential forensic indicators of material process history. A novel technique for synthesizing PuCl3 from the in situ chlorination of plutonium metal with HCl was developed to establish these signatures. Cerium metal surrogates were utilized to ensure optimization of the plutonium experiments and to minimize personnel exposure, and all experiments were carried out in a Raman reaction chamber designed for air‐tight, high vacuum environments. In situ Raman spectroscopy was employed in conjunction with density functional theory (DFT) to investigate the vibrational modes of PuCl3. Associated mixed oxy and hydroxyl phases are also reported. The combined Raman and DFT results have eliminated inconsistencies in Raman mode assignments for the MX3 family of metal chlorides having P63/m symmetry, and IR modes derived from the DFT calculations are additionally presented. The data observed in this study are of potential interest to nuclear forensic analyses, nuclear sample aging, nuclear energy, plutonium processing, and stockpile stewardship.

Nanostructured cauliflowers patterning in Zr doped tungsten oxide thin films grown by AACVD

The effort is made to grow the cellular segmentation patterning of undoped and Zr doped Tungsten Oxide (ZWO) coatings engineered by aerosol assisted Chemical Vapor Deposition (AACVD) onto silica glass at 400 °C. Nanostructured cauliflowers were successfully grown without using any particular template via the chemical route of AACVD for undoped and Zr doped Tungsten Oxide. The tailored coatings of nano cauliflowers were explored by employing FE-Scanning electron microscopy/Energy Dispersive X-ray spectroscopy (FE-SEM/EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), Fourier transformation Infrared spectroscopy (FTIR), UV-VIS spectroscopy (UV-VIS) and four-point probe method to study surface morphological, chemical composition, optical and electrical properties systematically. Morphological features present fractal-type cauliflower patterning because of Zr incorporation. XRD spectra revealed a monoclinic (WO3) phase in undoped Tungsten Oxide with preferential orientation (0 2 0) whereas Zr doping triggered the growth of Magneli suboxide W5O14 with tetragonal (0 0 1) preferred reflection. Adding Zr dopant caused a slight expansion of lattice with a decrease in crystallite size (54–18) nm. Vibrational information exhibits shoulder at around 854.30 cm−1, attributed to O–W–O bond shifting. Undoped and Zr doped Tungsten oxide thin film signatures positioned at 446.65 cm-1, 692 cm-1, and 854.30 cm-1 are witnessed with a red and blue shift in all rest of the Zr doped thin films. The mismatch of W and Zr ions in ionic radii, electronegativity, and thermal coefficients promote stresses leading to the variation in lattice parameters, bond length, and crystallite size with stretching of IR modes attributed to the incorporation of Zr into the host lattice sites of Tungsten oxide. XPS deconvoluted peaks yield the analysis for bond energy of O1s electrons located around 505.19 eV and 510.85 eV characterized as metallic oxide of Tungsten (WO3). UV-VIS spectroscopy presented a highly absorptive nature of coatings in the spectral range between (300–900) nm with the widening of both direct (1.9–3.2) eV and indirect (1.9–2.6) eV band gap which is of absolute interest for both fundamental and applied aspects. Transport properties unveiled the decrease of electrical resistivity of order from 106 Ω-cm (undoped) to 105 Ω-cm (Zr doped), attributed to grown high angle nanoparticles boundaries of tungsten oxide contribute to governing of nano cauliflowers and, as a result, the volume of the grain boundaries increases. The interplay between crystalline quality, tuned architecture, and oxygen vacancies can contribute to the understanding of morphological, optical, and transport properties.

DFT‐based systematic study on the structural, optoelectronic, thermodynamic, vibrational, and mechanical behavior of Ruddlesden Popper perovskites Sr2XO4 (X = Zr, Hf) for optoelectronic applications

AbstractDFT study on the structural, optoelectronic, thermodynamic, vibrational, and mechanical properties of Ruddlesden Popper (RP) perovskites Sr2XO4 (X = Zr, Hf) is made with the help of first principle simulation in the framework of WIEN2K code. The lattice constants in bohr unit are found to be for Sr2ZrO4, and for Sr2HfO4. The calculated band gap values are 2.65 eV for Sr2ZrO4 and 2.58 eV for Sr2HfO4. The band structure and electronic density of states reveal the semiconductor nature of these materials having an indirect band gap. Also, Kramers–Krönig relations are used for optical analysis which unveils that these compounds are suitable for applications in optoelectronic. The vibrational investigations are done while using harmonic approximation. Phonon dispersion curves are plotted to observe the vibrational modes by DFPT to confirm the dynamical stability of studied compounds. Although few soft modes have appeared, however, these compounds are found to be thermally stable. Raman modes appeared at low and high frequencies whereas IR modes are noticed at intermediate frequencies for considered compounds. Upon thermodynamical examination, the maximum value of free energy at 1000 K is noted to be −1.95 eV for Sr2ZrO4 and −2.25 eV for Sr2HfO4. The elastic constants are calculated by using the Voigt–Reuss–Hill approximation. The calculated anisotropic values for these compounds are 1.077 (A) and 0.913 (A) which indicate that Sr2ZrO4 has isotropic behavior and Sr2HfO4 has anisotropic behavior. From our calculations, Voigt Young's modulus of Sr2ZrO4 and Sr2HfO4 is 266.99 (GPa) and 279.42 (GPa) along with Poison's ratio of 0.29 and 0.26, respectively.

Infrared and Raman spectroscopy investigations in mullite-type Bi2(FexGa1-x)4O9 polycrystals

Mullite-type Bi2(FexGa1-x)4O9 (0 ≤ x ≤ 1) oxides, prepared by mecanochemical-thermal synthesis, were investigated by FTIR and Raman spectroscopies. Similarly to other mullite systems, IR (850–400 cm−1) and Raman bands (750–300 cm−1) are attributed to stretching and bending vibrations of tetrahedral and octahedral sites. A shift in the peak positions toward lower wavenumbers with the increase of iron content is observed. High-energy IR modes show only the presence of Ga-O-Ga and Ga-O-Fe/Fe-O-Ga stretching vibrations for x < 0.5. Raman bands between 500 cm−1 and 400 cm−1 revealed double band splitting for x < 0.5.

Investigation of flexible electrochemical storage with Li+/PVdF-HFP/PEO blend

ABSTRACT Design and development of lithium ion batteries with flexible solid polymer electrolyte along with high ionic conductivity is crucial and challenging so as to protect from electrical short circuits within electrochemical devices. The present research work describes the fabrication of lithium based solid polymer electrolytes (LSPEs) using polymer blends of poly (vinylidene fluoride- hexafluoropropylene) (PVdF-HFP), poly (ethylene oxide) (PEO) with selective weight ratios of lithium trifluoromethanesulfonate (LiCF3SO3) salt by using solution-cast approach. The scanning electron microscopy (SEM) exposed morphology of LSPE membranes depicts crosslinking of polymer network with salt elevates strong dissociation behavior of LiCF3SO3. The amorphous behavior of LSPEs explored using X-ray diffraction (XRD) crystallographs clearly accommodates reduction of average crystallite size from 10─6 m to 10─9 m. The complexation studies, bond length and force constants calculations, interaction of ions, ionic pairs and aggregates of LiCF3SO3 in LSPE films were briefly analyzed using Fourier transform infrared spectroscopy (FTIR). IR modes correspond to [δs (SO3)], [υas (SO3)], [υas (CF3)], and amorphous phase of PVdF-HFP results in complexation, whereas IR modes correspond to [δas (SO3)], [δs (CF3)], [δas (CF3)], [υs (SO3)], C=O and β-phase of PVdF-HFP attributes ionic pairs and aggregation phenomena. The [υs (SO3)] mode contribution toward ionic conductivity was detailed. The ionic conductivity (σionic) values were estimated using Electrochemical impedance spectroscopy (EIS). The σionic values were enhanced from 10─7 S/cm to 10─4 S/cm as salt concentration increases. Charge accumulation, ionic strength, and transference number analysis of LSPE membranes were investigated using Chronoamperometry and Cyclic Voltammetry. Further, we have fabricated flexible electrochemical storage device (FESD) which are accentuating carriers of smart electronics technology (SET) in terms of foldable and stretchable electronic devices. We have explored discharge characteristics of our FESD with an average discharge current of 3 mA for 25 hours and denoted using 0.04C rating.

Pressure-Induced Monoclinic to Tetragonal Phase Transition in RTaO4 (R = Nd, Sm): DFT-Based First Principles Studies

In this manuscript, we report the density functional theory-based first principles study of the structural and vibrational properties of technologically relevant M′ fergusonite (P2/c)-structured NdTaO4 and SmTaO4 under compression. For NdTaO4 and SmTaO4, ambient unit cell parameters, along with constituent polyhedral volume and bond lengths, have been compared with earlier reported parameters for EuTaO4 and GdTaO4 for a better understanding of the role of lanthanide radii on the primitive unit cell. For both the compounds, our calculations show the presence of first-order monoclinic to tetragonal phase transition accompanied by nearly a 1.3% volume collapse and an increase in oxygen coordination around the tantalum (Ta) cation from ambient six to eight at phase transition. A lower bulk modulus obtained in the high-pressure tetragonal phase when compared to the ambient monoclinic phase is indicative of the more compressible unit cell under pressure. Phonon modes are calculated for the ambient and high-pressure phases with compression for both the compounds along with their pressure coefficients. One particular IR mode has been observed to show red shift in the ambient monoclinic phase, possibly leading to the instability in the compounds under compression.

Raman and Structural Characterization of Spinel Compound Zn8/5Al4/15TiO4

Microwave dielectric materials have been attracted enormous attention for their application in microwave communication. A new microwave dielectric material with composition Zn8/5Al4/15TiO4 was synthesized by conventional solid-state reaction method. The structure of Zn8/5Al4/15TiO4 was refined with the cubic P4332 space group (number of formula unit per unit cell, Z = 4). The Rietveld refinement study revealed the theoretical density ρ = 4.80 g/cm3 and lattice parameter a = 8.405 Å. This compound was crystallized in cubic spinel structure and 1:3 ordering was observed on the octahedral sites. Raman spectrum of the compound was collected at room temperature. Theoretical Factor group analysis for this compound predicts 40 Raman modes and 22 IR modes. However, experimentally 13 vibrational modes have been observed in the Raman spectrum which can be separated into internal TiO6 vibration and external rotation and translation TiO6 modes. Raman modes in the range of 500-800 cm-1 are assigned to internal vibrational modes.

Study of vibrational spectra of zwitterionic 3-Aminobutanoic acid, as supported by DFT calculations

3-Aminobutanoic acid is an unnatural amino acid and by analogy with other amino acids, is represented in its zwitterionic form by R-CH(COO¯)NH­3+ (where side group R = aryl, alkyl or any other group) in solid phase. Experimental IR and Raman modes near 3029, 2871, 1577, 1288 cm-1 measured for 3ABA are strongly in favor of the zwitterionic dimer structure formed of –N-H∙∙∙O–C bonding between –NH­3+ and anion – CO2¯ groups. Zwitterionic monomer and dimer structures at B3LYP/6-311++G(d,p) level are computed. It has been found that the stable zwitterionic monomer and dimer structures are possible only in a water solvent medium computed using SCRF SMD solvation model. The zwitterionic dimer vibrational structure is in good agreement with the experiment and both zwitterionic monomer and dimer models have identically predicted the frequencies of the modes that are localized and unperturbed except those that characterize the H-bonding due to the –N-H∙∙∙O bonding. This is supported by the appearance of two characteristic medium strong Raman modes at 900 and 843 cm-1 that suggest unperturbed C-C skeletal structure and localized modes due to CH, CH2 and CH3 groups bound to it.

Elucidating the phase transitions of decanoic-acid crystal by XRD, Raman, group theory and Gibbs energy analyses combined with DFT calculations

This research reports a series of phase transitions in the decanoic-acid (DA) crystal under low-temperature conditions, which were elucidated by XRD, Raman scattering and DFT calculations in a dimer of DA in the C form (monoclinic structure). The first phase change was noticed within the 210–190 K interval duly characterized as a transition of second-order type, as indicated by Gibbs energy behavior, suggesting that the monoclinic structure (P21/c) of the crystal is not changed. The second change was observed nearly 110–90 K, whose transition is first-order type occurring from the C form to an A form (triclinic), possibly belonging to the P1 space group. This new polymorphic phase was duly predicted through DFT calculations. According to Gibbs energy behavior, the third phase change (∼30–10 K) is proposed to be a transition from the A form to a new polymorphic phase that probably is a first-order transition, likely associated with a change from the P1 space group to P-1. Furthermore, group theory and wavenumber vs temperature plots’ analyses corroborated the phase transitions undergone by DA crystal. In addition, anharmonicity effects in several Raman bands’ behavior were noticed during the cooling. A correct assignment for the Raman and IR modes via DFT calculations at room-temperature conditions is also provided herein.

Locality determination of inky black omphacite jades from Myanmar and Guatemala by nondestructive analysis

AbstractLocality identification of high‐quality inky black omphacite jades (inky jades) from Myanmar and Guatemala is becoming increasingly urgent. In this study, Raman, Fourier transform infrared (FTIR), and energy‐dispersive X‐ray fluorescence spectroscopy (EDXRF) were performed to distinguish samples of inky jade from the two localities. The Raman spectra revealed the presence of several types of minor minerals in Guatemalan samples, including titanite, albite, orthoclase, taramite, celsian, and cymrite, whereas the Myanmar samples consisted almost entirely of omphacite. Taramite and lath‐like celsian occurred only in Guatemalan samples and had significance in locality tracing. The Raman and FTIR reflectance spectra of omphacite shifted to low wavenumbers in proportional to isomorphic substitution Na+Al3+ → Ca2+(Mg2+, Fe2+). Semiquantitative calculations based on the Raman (~680 cm−1) and IR modes (~658, ~576, and ~424 cm−1) showed consistent jadeite end‐member components (~43% to ~64%) in the Myanmar samples, whereas those (~23% to ~87.5%) of the Guatemalan samples were wider and generally lower. In addition, the full width at half maximum values (FWHMs) of Raman shifts near 680 cm−1 in the Myanmar samples (avg. 15.03 cm−1) were less than those (avg. 16.81 cm−1) of the Guatemalan specimens. Linear discriminant analysis (LDA) based on Raman spectroscopy identified most samples with accuracy of 85.5%. Combined with results by EDXRF, these analyses revealed the characteristics of a relatively narrow range of Na+Al3+ → Ca2+Mg2+ isomorphism for the Myanmar jades and a more developed Na+Al3+ → Ca2+(Mg2+, Fe2+) isomorphism for the Guatemalan jades. This study might have implications for commercial applications, archeological research, and judicial expertise.

Relationship between distortion of crystal structure and dielectric properties of complex perovskite oxide Ba(Co,Zn)1/3Nb2/3O3 thin films

The oxygen octahedral can be distorted by epitaxial strain due to the lattice mismatch. The epitaxial strain (εyy) linearly decreases from − 0.244% to − 0.445% with the growth temperature. Thin films grow along c axis on the SrTiO3 substrate and exhibit the epitaxial relationship of Ba(Co,Zn)1/3Nb2/3O3 (001) // SrTiO3 (001). The superlattice reflections arising from in-phase tilting of the oxygen octahedra are clearly visible along [010] and [111] zone axis. The IR modes at 330 cm−1 and 390 cm−1 related to in-phase tilting are observed in far-infrared reflectivity spectroscopy. The calculated Q×f values from far-infrared reflectivity spectra of films grown at 550 °C to 700 °C increases from 51,000 GHz to 91,000 GHz mainly due to the enhancement of crystalline quality. The intrinsic quality factor (Q) is mainly contributed by O-(Co, Nb)-O and O-(Zn, Nb)-O bonding modes, while in-phase tilting in BCZN films may result in enhanced dielectric constants.

Calculation Of Gruneisen Parameter, Compressibility, And Bulk Modulus as Functions Of Pressure In (C6H5CH2NH3)2 PBI4

Hybrid organic-inorganic perovskites (HOIPs) exhibit multiple structural phase transitions, which result in enhanced mechanical and electronic properties of these perovskites. Order-disorder of organic components was thought to be the main factor to cause these phase transitions up to the last decade; however, recent research about HOIPs have shown that the structural phase transition also occurs with the induced pressure or temperature. The research studies related to the pressure have attracted a great deal of scholarly interest due to its contribution to the func-tionality of HOIPs in many current applications. Two-dimensional halide perovskites having been synthesized in the last few years have been increasingly studied thanks to its superior hysteresis in flexibility and mechanical properties under pressure. It is important to understand and model theoretically how induced pressure affects mechanical and electronic properties of (PMA)2PbI4 in order to develop new potential applications in optoelectronics. In this study, the isothermal mode-Grüneisen parameter, the isothermal compressibility, and the bulk modulus were calculated as functions of pressure at ambient temperature by using the calculated Raman frequencies and observed volume data for the selected IR modes in (PMA)2PbI4. These calculated parameters were compared with the observed measurements reported for the Pbca, Pccn and Pccn (isostructural) phases in the studied perovskites. The results obtained in the present study, which were highly compatible with the experimental measurements, showed that (PMA)2PbI4 is usable in optoelectronic applications.

Perfluoropentacene thin films on Au(1 1 1) surfaces: Effect of kinetic energy and vibrational properties

We studied vibrational properties and the effect of beam kinetic energy on perfluoropentacene (PFP) thin films grown by supersonic molecular beam deposition (SMBD) technique on gold surfaces. Though similar growth mechanism was observed for different beam kinetic energies, in the case of low coverage (less than 1 monolayer) films and for low deposition rates significant differences were observed in the properties of films grown by using helium and argon carrier gasses with the former case resulting in higher average grain size. For multilayer films however there were no significant differences between helium and argon grown films. Vibrational properties were investigated by using Infrared Scattering-type Scanning Nearfield Optical Microscopy (s-SNOM) on clean and m-carborane-1-thiol (M1) coated template-stripped gold (TSAu) substrates. For both substrates thick PFP films (15 nm) had similar spectra whereas there were significant differences in the spectra of thin films (1 nm) due to PFP-substrate interactions. Davydov splitting of the IR modes were observed for both 1 nm and 15 nm films indicating similar molecular arrangements in both type of films.