We report a temperature-dependent Raman scattering investigation of the multiferroic material bismuth ferrite ${\mathrm{BiFeO}}_{3}$ (BFO). The observed loss spectrum at ferroelectric Curie temperature ${T}_{C}$ should be in agreement with cubic $Pm\overline{3}m$ structure high-temperature paraelectric phase. Surprisingly, ferroelectric-to-paraelectric phase transition is not soft-mode driven, indicating nonconventional ferroelectric. Furthermore, our results reveal pronounced phonon...

We report high-pressure Raman measurements (up to 19 GPa) on the perovskite-type relaxor ferroelectric sodium-bismuth-titanate, ${\mathrm{Na}}_{0.5}{\mathrm{Bi}}_{0.5}{\mathrm{TiO}}_{3}$ (NBT). Distinct changes in spectra have been analyzed light of a rhombohedral-to-orthorhombic $(R3c\ensuremath{-}\mathrm{t}\mathrm{o}\ensuremath{-}\mathit{Pnma})$ phase transition. Results show that this transition, involving change tilt system and cation displacement, does not occur single step, but goes...

Ab initio simulations and experimental techniques are combined to reveal that, unlike what was commonly accepted for more than 30 years, perovskites related materials enhance their ferroelectricity as hydrostatic pressure increases above a critical value. This unexpected high-pressure is different in nature from conventional because it driven by an original electronic effect rather long-range interactions.

We report experimental evidence for pressure instabilities in the model multiferroic ${\text{BiFeO}}_{3}$ and, namely, reveal two structural phase transitions around 3.5 and 10 GPa by using diffraction far-infrared spectroscopy at a synchrotron source. The intermediate crystallizes monoclinic space group, with octahedra tilts small cation displacements. When is increased further displacements (and thus polar character) of suppressed above GPa. nonpolar orthorhombic $Pnma$ structure observed...

The equation of state KCl and KBr, compressed in a helium pressure medium diamond-anvil cell, has been measured by x-ray diffraction the B1 B2 phases up to 165 GPa at 298 K. $P$-$V$-$T$ KBr calculated ab initio molecular dynamics wide compression range 7000 thermal exhibits linear behavior with temperature remains low under high compression. experimental $P$-$V$ points have used set high-pressure--high-temperature KBr. With these equations state, can be as markers laser-heated...

Many of the outstanding properties in oxides are related to materials with an intrinsic nanoscaled local structure, where different regions characterized by competing chemical, structural, and/or physical properties. One major challenges analysis is experimental access properties, which often at best a difficult task, fact that inhibits understanding such as colossal magnetoresistance, giant piezoelectricity, and high-temperature superconductivity. Here we present investigation relaxor...

The structure of nanocrystallized zirconia has been investigated in the 1--40-GPa pressure range at ambient temperature. A continuous transformation towards ideal fluorite cubic is observed from 8 GPa. complete seems to be achieved 30 compressibility tetragonal and forms are derived discussed.

We investigate the cubic to tetragonal phase transition in pressure-temperature diagram of strontium titanate SrTiO3 (STO) by means Raman spectroscopy and X-ray diffraction on single crystal samples. experiments are performed at room temperature, 381 467 K up 53 GPa, 30 GPa 26 respectively. The observation superstructure reflections patterns provides evidence that undergoes all investigated temperatures a pressure-induced from I4/mcm phase, identical low-temperature phase. No other is...

We report a room-temperature high-pressure x-ray and Raman scattering investigation of lead titanate (PbTiO3) up to 63 GPa. Three continuous phase transitions at 13, 20, 45 GPa between tetragonal-like phases occur. As result, no evidence is found for pressure-induced morphotropic boundary. Our study provides experimental that PbTiO3 presents complex sequence accommodating pressure through mechanisms involving oxygen octahedra tilting reentrance ferroelectricity.

We investigate the high-pressure phase transitions in BiFeO${}_{3}$ by single-crystal and powder x-ray diffraction, as well Raman spectroscopy. Six are reported 0--60-GPa range. At low pressures, four evidenced at 4, 5, 7, 11 GPa. In this range, crystals display large unit cells complex domain structures, which suggests a competition between tilt systems possibly off-center cation displacements. The nonpolar $Pnma$ remains stable over pressure range 38 GPa, where distortion (tilt angle)...

We report high-pressure Raman measurements (up to 27 GPa) on the perovskite-type relaxor ferroelectric ${\mathrm{BaTi}}_{0.65}{\mathrm{Zr}}_{0.35}{\mathrm{O}}_{3}({\mathrm{BTZ}}_{35}).$ Distinct changes of spectra with increasing pressure illustrate that ${\mathrm{BTZ}}_{35}$ presents important instabilities leading at least two phase transitions around 5.7 GPa and 15.1 GPa, respectively. The observed pressure-induced spectral for are reminiscent features have been pure...

We report on a study of pressure-dependent structural properties LaAlO3, which is considered to be model material the class `tilted' perovskites. Our high-pressure investigation by means Raman spectroscopy and synchrotron radiation shows that LaAlO3 presents instabilities under pressure undergoes soft-mode-driven rhombohedral-to-cubic phase transition in vicinity 14 GPa, can analysed framework Landau model. The changes are described terms collective restoring initially tilted AlO6 octahedra...

The perovskite Bismuth ferrite BiFeO3 (BFO) is considered to be a model multiferroic and offers rare multiferroelectric robustness since it presents coexistence of ferroelectric antiferromagnetic order up unusually high temperatures. Perovskite-type materials are known for their common structural instabilities which can driven by diverse external parameters like temperature, pressure, stress etc. Such the associated distortions often very subtle difficult detect techniques probing average...

The high-pressure behavior of elemental Sn has been studied by angle-dispersive synchrotron x-ray diffraction up to 138 GPa under quasihydrostatic conditions at room temperature. data confirm the occurrence a first-order phase transition 10.8 between $\ensuremath{\beta}$-Sn (Sn-II) ($I{4}_{1}/amd$) and further body-centered-tetragonal polymorph ($\ensuremath{\gamma}$-Sn or Sn-III) ($I4/mmm$). Above 32 GPa, this exhibits distortion into new body-centered-orthorhombic (bco) modification...

We report results of a high-pressure investigation by Raman spectroscopy classic relaxor ferroelectric (relaxor) ${\mathrm{PbMg}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_{3}$ (PMN), which is considered to be model system for the understanding and relaxor-related materials. The observed pressure-dependent spectra are very unusual, pointing relaxor-specific spectral signature. further show that an external pressure several GPa, as can met in thin films, alters fundamentally structural polar...

We report an investigation of the relaxor ferroelectric PbMg(1/3)Nb(2/3)O3 by combining external parameter high pressure with x-ray diffuse scattering. The observed total suppression relaxor-characteristic scattering is unusual and points to important pressure-induced changes in local order. behavior might well be a general feature ferroelectrics under pressure.

The structural behaviour of SnS under high-pressure has been investigated by angular dispersive synchrotron powder diffraction up to 38.5 GPa. A phase transition from orthorhombic α-SnS monoclinic γ-SnS was observed at 18.15 fit a Birch–Murnaghan equation-of-state gave the volume zero pressure V0 = 192.6(3) Å3, bulk modulus B0 36.6(9) GPa and derivative for 160(1) Å, 86.0(5) γ-SnS. improper ferro-elastic is first-order accompanied large discontinuity about 9.1%. can be described in terms...

In this work, we investigate calcium titanate (CaTiO3 - CTO) using X-ray diffraction and Raman spectroscopy up to 60 55 GPa respectively. Both experiments show that the orthorhombic Pnma structure remains stable highest pressures measured, in contradiction ab-initio predictions. A fit of compression data with a second-order Birch-Murnaghan equation state yields bulk modulus K0 181.0(6) GPa. The distortion is found increase slightly pressure, agreement previous at lower general rules for...

An overview of several innovations regarding in situ laser-heating techniques the diamond anvil cell at high-pressure beamline ID27 European Synchrotron Radiation Facility is presented. Pyrometry measurements have been adapted to allow simultaneous double-sided temperature with installation two additional online laser systems: a CO2 and pulsed Nd:YAG system. This reiteration advancements designed pave way for new generation state-of-the-art experiments that demand need synchrotron...