0000000001307822
AUTHOR
Jordi Ibáñez
Phase diagram of calcium at high pressure and high temperature
Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murn…
Optical emission fromSiO2-embedded silicon nanocrystals: A high-pressure Raman and photoluminescence study
We investigate the optical properties of high-quality Si nanocrystals $(\mathrm{NCs})/\mathrm{Si}{\mathrm{O}}_{2}$ multilayers under high hydrostatic pressure with Raman scattering and photoluminescence (PL) measurements. The aim of our study is to shed light on the origin of the optical emission of the Si $\mathrm{NCs}/\mathrm{Si}{\mathrm{O}}_{2}$. The Si NCs were produced by chemical-vapor deposition of Si-rich oxynitride $(\mathrm{SRON})/\mathrm{Si}{\mathrm{O}}_{2}$ multilayers with 5- and 4-nm SRON layer thicknesses on fused silica substrates and subsequent annealing at 1150 \ifmmode^\circ\else\textdegree\fi{}C, which resulted in the precipitation of Si NCs with an average size of 4.1 a…
High-pressure optical absorption in InN: Electron density dependence in the wurtzite phase and reevaluation of the indirect band gap of rocksalt InN
We report on high-pressure optical absorption measurements on InN epilayers with a range of free-electron concentrations (5×1017–1.6×1019 cm−3) to investigate the effect of free carriers on the pressure coefficient of the optical band gap of wurtzite InN. With increasing carrier concentration, we observe a decrease of the absolute value of the optical band gap pressure coefficient of wurtzite InN. An analysis of our data based on the k·p model allows us to obtain a pressure coefficient of 32 meV/GPa for the fundamental band gap of intrinsic wurtzite InN. Optical absorption measurements on a 5.7-μm-thick InN epilayer at pressures above the wurtzite-to-rocksalt transition have allowed us to o…
Reversible Tuning of Ca Nanoparticles Embedded in a Superionic CaF2 Matrix
Controlling the size and shape of metallic colloids is crucial for a number of nanotechnological applications ranging from medical diagnosis to electronics. Yet, achieving tunability of morphological changes at the nanoscale is technically difficult and the structural modifications made on nanoparticles generally are irreversible. Here, we present a simple nonchemical method for controlling the size of metallic colloids in a reversible manner. Our strategy consists of applying hydrostatic pressure on a Ca cationic sublattice embedded in the irradiated matrix of CaF2 containing a large concentration of defects. Application of our method to CaF2 along with in situ optical absorption of the Ca…
GdBO3 and YBO3 crystals under compression
High-pressure X-ray diffraction studies on nanocrystals of the GdBO3 and YBO3 rare-earth orthoborates are herein reported up to 17.4(2) and 13.4(2) GPa respectively. The subsequent determination of the room-temperature pressure-volume equations of state is presented and discussed in the context of contemporary publications which contradict the findings of this work. In particular, the isothermal bulk moduli of GdBO3 and YBO3 are found to be 170(13) and 163(13) GPa respectively, almost 50% smaller than recent findings. Our experimental results provide an accurate revision of the high-pressure compressibility behaviour of GdBO3 and YBO3 which is consistent with the known systematics in isomor…
Comparative study of the high-pressure behavior of ZnV2O6, Zn2V2O7, and Zn3V2O8
We report a study of the high-pressure structural behavior of ZnV2O6, Zn2V2O2, and Zn3V2O8, which has been explored by means of synchrotron powder x-ray diffraction. We found that ZnV2O6 and Zn3V2O8 remain in the ambient-pressure structure up to 15 GPa. In contrast, in the same pressure range, Zn2V2O2 undergoes three phase transitions at 0.7, 3.0, and 10.8 GPa, respectively. Possible crystal structures for the first and second high-pressure phases are proposed. Reasons for the distinctive behavior of Zn2V2O2 are discussed. The compressibility of the different polymorphs has been determined. The response to pressure is found to be anisotropic in all the considered compounds and the room-temp…
Pressure dependence of the refractive index in wurtzite and rocksalt indium nitride
We have performed high-pressure Fourier transform infrared reflectance measurements on a freestanding InN thin film to determine the refractive index of wurtzite InN and its high-pressure rocksalt phase as a function of hydrostatic pressure. From a fit to the experimental refractive-index curves including the effect of the high-energy optical gaps, phonons, free carriers, and the direct (fundamental) band-gap in the case of wurtzite InN, we obtain pressure coefficients for the lowfrequency (electronic) dielectric constant e1 . Negative pressure coefficients of -8.8 × 10-2 GPa-1 and -14.8 × 10-2 GPa-1 are obtained for the wurtzite and rocksalt phases, respectively. The results are discussed …
High-pressure lattice dynamics in wurtzite and rocksalt indium nitride investigated by means of Raman spectroscopy
We present an experimental and theoretical lattice-dynamical study of InN at high hydrostatic pressures. We perform Raman scattering measurements on five InN epilayers, with different residual strain and free electron concentrations. The experimental results are analyzed in terms of ab initio lattice-dynamical calculations on both wurtzite InN (w-InN) and rocksalt InN (rs-InN) as a function of pressure. Experimental and theoretical pressure coefficients of the optical modes in w-InN are compared, and the role of residual strain on the measured pressure coefficients is analyzed. In the case of the LO band, we analyze and discuss its pressure behavior considering the double-resonance mechanis…
Unveiling the role of the lone electron pair in sesquioxides at high pressure: compressibility of β-Sb2O3
The structural, vibrational and electronic properties of the compressed beta-Sb2O3 polymorph, a.k.a. mineral valentinite, have been investigated in a joint experimental and theoretical study up to 23 GPa. The compressibility of the lattice parameters, unit-cell volume and polyhedral unit volume as well as the behaviour of its Raman- and IR-active modes under compression have been interpreted on the basis of ab initio theoretical simulations. Valentinite shows an unusual compressibility up to 15 GPa with four different pressure ranges, whose critical pressures are 2, 4, and 10 GPa. The pressure dependence of the main structural units, the lack of soft phonons, and the electronic density char…
High-pressure/high-temperature phase diagram of zinc
The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300K up to the melting temperature. The pressure at which c/a reaches root 3 (approximate to 10GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple pol…
High-Pressure High-Temperature Stability and Thermal Equation of State of Zircon-Type Erbium Vanadate.
Inorganic chemistry 57(21), 14005 - 14012 (2018). doi:10.1021/acs.inorgchem.8b01808
CSD 1852498: Experimental Crystal Structure Determination
Related Article: Javier Ruiz-Fuertes, Domingo Martínez-García, Tomás Marqueño, Daniel Errandonea, Simon G. MacLeod, Thomas Bernert, Eiken Haussühl, David Santamaría-Pérez, Jordi Ibáñez, Anitha Mallavarapu, S. Nagabhusan Achary, Catalin Popescu, and Marco Bettinelli|2018|Inorg.Chem.|57|14005|doi:10.1021/acs.inorgchem.8b01808
CSD 1852499: Experimental Crystal Structure Determination
Related Article: Javier Ruiz-Fuertes, Domingo Martínez-García, Tomás Marqueño, Daniel Errandonea, Simon G. MacLeod, Thomas Bernert, Eiken Haussühl, David Santamaría-Pérez, Jordi Ibáñez, Anitha Mallavarapu, S. Nagabhusan Achary, Catalin Popescu, and Marco Bettinelli|2018|Inorg.Chem.|57|14005|doi:10.1021/acs.inorgchem.8b01808
CSD 1852497: Experimental Crystal Structure Determination
Related Article: Javier Ruiz-Fuertes, Domingo Martínez-García, Tomás Marqueño, Daniel Errandonea, Simon G. MacLeod, Thomas Bernert, Eiken Haussühl, David Santamaría-Pérez, Jordi Ibáñez, Anitha Mallavarapu, S. Nagabhusan Achary, Catalin Popescu, and Marco Bettinelli|2018|Inorg.Chem.|57|14005|doi:10.1021/acs.inorgchem.8b01808
CSD 1852496: Experimental Crystal Structure Determination
Related Article: Javier Ruiz-Fuertes, Domingo Martínez-García, Tomás Marqueño, Daniel Errandonea, Simon G. MacLeod, Thomas Bernert, Eiken Haussühl, David Santamaría-Pérez, Jordi Ibáñez, Anitha Mallavarapu, S. Nagabhusan Achary, Catalin Popescu, and Marco Bettinelli|2018|Inorg.Chem.|57|14005|doi:10.1021/acs.inorgchem.8b01808
CSD 1852501: Experimental Crystal Structure Determination
Related Article: Javier Ruiz-Fuertes, Domingo Martínez-García, Tomás Marqueño, Daniel Errandonea, Simon G. MacLeod, Thomas Bernert, Eiken Haussühl, David Santamaría-Pérez, Jordi Ibáñez, Anitha Mallavarapu, S. Nagabhusan Achary, Catalin Popescu, and Marco Bettinelli|2018|Inorg.Chem.|57|14005|doi:10.1021/acs.inorgchem.8b01808
CSD 1852500: Experimental Crystal Structure Determination
Related Article: Javier Ruiz-Fuertes, Domingo Martínez-García, Tomás Marqueño, Daniel Errandonea, Simon G. MacLeod, Thomas Bernert, Eiken Haussühl, David Santamaría-Pérez, Jordi Ibáñez, Anitha Mallavarapu, S. Nagabhusan Achary, Catalin Popescu, and Marco Bettinelli|2018|Inorg.Chem.|57|14005|doi:10.1021/acs.inorgchem.8b01808