Vibrational properties of SrCu2O2 studied via Density Functional Theory calculations and compared to Raman and infrared spectroscopy measurements

International audienceThe SrCu2O2 material is a p-type transparent conductive oxide. A theoretical study of the SrCu2O2 crystal is performed with a state of the art implementation of the Density Functional Theory. The simulated crystal structure is compared with available X-ray diffraction data and previous theoretical modeling. Density Functional Perturbation Theory is used to study the vibrational properties of the SrCu2O2 crystal. A symmetry analysis of the optical phonon eigenvectors at the Brillouin zone center is proposed. The Raman spectra simulated using the derivatives of the dielectric susceptibility, show a good agreement with Raman scattering experimental results

Prediction of Martensite Start Temperature for Lightweight Fe–Mn–Al–C Steels

A tailor-made thermodynamic database of the Fe-Mn-Al-C system was developed using the CALPHAD approach. The database enables predicting phase equilibria and thereby assessing the resulting microstructures of Fe-Mn-Al-C alloys. Available information on the martensite start (Ms) temperature was reviewed. By employing the Ms property model in the Thermo-Calc software together with the new thermodynamic database and experimental Ms temperatures, a set of model parameters for the Fe-Mn-Al-C system in the Ms model was optimised. Employing the newly evaluated parameters, the calculated Ms temperatures of the alloys in the Fe-Mn-Al-C system were compared with the available measured Ms temperatures. Predictions of Ms temperatures were performed for the alloys, Fe-10, 15 and 20 wt. Mn-xAl-yC. The predictability of the Ms model can be further validated when new experimental Ms temperatures of the Fe-Mn-Al-C system are available. © 2018, The Author(s)

Optical, microstructural, vibrational and theoretical studies of p-type SrCu2O2 and BaCu2O2 Transparent Conductive Oxides

International audienceTransparent conducting metal oxides (TCO) are unusual semiconducting materials displaying transparency to visible light. TCO materials are used for electrostatic shielding, antistatic screens, transparent heating devices, solar cells and even organic light emitting diodes. However, most TCOs are n-type, while p-type TCOs are scarce. SrCu2O2 is a leading candidate as a p-type transparent conductive oxide. In this paper, we report theoretical calculations and experimental studies on the vibrational, optical and microstructural properties of both bulk and thin films of polycrystalline undoped SrCu2O2 obtained by pulsed laser deposition (PLD). Barium doping of the SrCu2O2 by substitution of Sr atoms is also reported. The simulated crystal structures of both SrCu2O2 and BaCu2O2 materials, obtained through a state-of-the-art implementation of the Density functional theory, are compared with experimental X-ray diffraction data of undoped and Ba-doped SrCu2O2 bulk materials. Raman spectra of both SCO and BCO materials are simulated from the derivatives of the dielectric susceptibility and a symmetry analysis of the optical phonon eigenvectors at the Brillouin zone center is proposed. Good agreement with Raman scattering experimental results is demonstrated

Optical and microstructural properties of p-type SrCu 2 O 2 : First principles modeling and experimental studies

Abstract In this paper, we report first principles calculations and experimental studies of the optical and microstructural properties of both bulk and thin films of SrCu 2 O 2 . Polycrystalline SrCu 2 O 2 films were grown by a conventional Pulsed Laser Deposition method in a flowing oxygen environment on corning glass 7059 and silicon substrates. Several characterization techniques, including X-ray diffraction (XRD), Fourier Transform IR (FTIR), Raman, spectroscopic ellipsometry, reflectance/transmission spectrophotometry and Atomic Force Microscopy have been used for the investigation of the microstructural and vibrational properties of both bulk and thin films of SrCu 2 O 2 . XRD shows that bulk SrCu 2 O 2 is polycrystalline and assumes the pure tetragonal phase of SrCu 2 O 2 . The vibrational properties of the tetragonal phase of SrCu 2 O 2 have been inferred from Raman and FTIR spectroscopies and for the first time both Raman and IR active modes have been assigned. The bulk polycrystalline SrCu 2 O 2 optical band gap determined from spectroscopic ellipsometry was 3.34 ± 0.01 eV. XRD results confirmed that pure non-textured polycrystalline phase SrCu 2 O 2 thin films with a smooth surface can be grown by PLD at low temperature (300°C)