Extreme conditions research using the large-volume press at the P61B endstation, PETRA III.

Penetrating, high-energy synchrotron X-rays are in strong demand, particularly for high-pressure research in physics, chemistry and geosciences, and for materials engineering research under less extreme conditions. A new high-energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front-end components and beam characteristics.

Plastic Deformation and Strengthening Mechanisms of Nanopolycrystalline Diamond.

Bulk nanopolycrystalline diamond (NPD) samples were deformed plastically within the diamond stability field up to 14 GPa and above 1473 K. Macroscopic differential stress Δσ was determined on the basis of the distortion of the 111 Debye ring using synchrotron X-ray diffraction. Up to ∼5(2)% strain, Debye ring distortion can be satisfactorily described by lattice strain theories as an ellipse.

Impact of Surface Roughness on Recrystallization of an α-AlO(001) Single Crystal to α-AlO(OH) Diaspore Microcrystals.

We demonstrate that the surface of an α-AlO(001) single crystal recrystallizes to α-AlO(OH) under ultrahigh pressure (8 GPa) at 600 °C. The recrystallization depends on the degree of surface roughness. A polished surface topotaxially recrystallizes to (100)-oriented α-AlO(OH) microcrystals, while unpolished surface recrystallizes to polycrystalline α-AlO(OH).

3D multiscale-imaging of processing-induced defects formed during sintering of hierarchical powder packings.

The characterization of the processing-induced defects is an essential step for developing defect-free processing, which is important to the assurance of structural reliability of brittle ceramics. The multiscale X-ray computed tomography, consisting of micro-CT as a wide-field and low-resolution system and nano-CT as a narrow-field and high-resolution system, is suitable for observing crack-like defects with small length and with very small crack opening displacement. Here we applied this powerful imaging tool in order to reveal the complicated three-dimensional morphology of defects evolved during sintering of alumina.

Picosecond amorphization of SiO stishovite under tension.

It is extremely difficult to realize two conflicting properties-high hardness and toughness-in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip.

Transparent polycrystalline cubic silicon nitride.

Glasses and single crystals have traditionally been used as optical windows. Recently, there has been a high demand for harder and tougher optical windows that are able to endure severe conditions. Transparent polycrystalline ceramics can fulfill this demand because of their superior mechanical properties.

Covalency-reinforced oxygen evolution reaction catalyst.

The oxygen evolution reaction that occurs during water oxidation is of considerable importance as an essential energy conversion reaction for rechargeable metal-air batteries and direct solar water splitting. Cost-efficient ABO3 perovskites have been studied extensively because of their high activity for the oxygen evolution reaction; however, they lack stability, and an effective solution to this problem has not yet been demonstrated. Here we report that the Fe(4+)-based quadruple perovskite CaCu3Fe4O12 has high activity, which is comparable to or exceeding those of state-of-the-art catalysts such as Ba(0.

Large increase in fracture resistance of stishovite with crack extension less than one micrometer.

The development of strong, tough, and damage-tolerant ceramics requires nano/microstructure design to utilize toughening mechanisms operating at different length scales. The toughening mechanisms so far known are effective in micro-scale, then, they require the crack extension of more than a few micrometers to increase the fracture resistance. Here, we developed a micro-mechanical test method using micro-cantilever beam specimens to determine the very early part of resistance-curve of nanocrystalline SiO2 stishovite, which exhibited fracture-induced amorphization.

Muonium in stishovite: implications for the possible existence of neutral atomic hydrogen in the earth's deep mantle.

Hydrogen in the Earth's deep interior has been thought to exist as a hydroxyl group in high-pressure minerals. We present Muon Spin Rotation experiments on SiO2 stishovite, which is an archetypal high-pressure mineral. Positive muon (which can be considered as a light isotope of proton) implanted in stishovite was found to capture electron to form muonium (corresponding to neutral hydrogen).

Fracture-induced amorphization of polycrystalline SiO2 stishovite: a potential platform for toughening in ceramics.

Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways.

Control of bond-strain-induced electronic phase transitions in iron perovskites.

Unusual electronic phase transitions in the A-site ordered perovskites LnCu3Fe4O12 (Ln: trivalent lanthanide ion) are investigated. All LnCu3Fe4O12 compounds are in identical valence states of Ln(3+)Cu(2+)3Fe(3.75+)4O12 at high temperature.

A-site-ordered perovskite MnCu3V4O12 with a 12-coordinated manganese(II).

A novel cubic perovskite MnCu3V4O12 has been synthesized at a high pressure and high temperature of 12 GPa and 1373 K. This compound crystallizes in the A-site-ordered perovskite structure (space group Im3) with lattice constant a = 7.26684(10) Å at room temperature.

Suppression of intersite charge transfer in charge-disproportionated perovskite YCu3Fe4O12.

A novel iron perovskite YCu3Fe4O12 was synthesized under high pressure and high temperature of 15 GPa and 1273 K. Synchrotron X-ray and electron diffraction measurements have demonstrated that this compound crystallizes in the cubic AA'3B4O12-type perovskite structure (space group Im3, No. 204) with a lattice constant of a = 7.

B-site deficiencies in A-site-ordered perovskite LaCu3Pt(3.75)O12.

An A-site-ordered perovskite LaCu3Pt(3.75)O12 was synthesized by replacing Ca(2+) with La(3+) in a cubic quadruple AA'3B4O12-type perovskite CaCu3Pt4O12 under high-pressure and high-temperature of 15 GPa and 1100 °C. In LaCu3Pt(3.

Pd(2+)-incorporated perovskite CaPd3B4O12 (B = Ti, V).

Novel A-site ordered perovskites CaPd(3)Ti(4)O(12) and CaPd(3)V(4)O(12) were synthesized under high-pressure and high-temperature of 15 GPa and 1000 °C. These compounds are the first example in which a crystallographic site in a perovskite-type structure is occupied by Pd(2+) ions with a 4d(8) low spin configuration. The ionic models for these compounds were determined to be Ca(2+)Pd(2+)(3)Ti(4+)(4)O(12) and Ca(2+)Pd(2+)(3)V(4+)(4)O(12) by structural refinement using synchrotron X-ray powder diffraction, hard X-ray photoemission, and soft X-ray absorption spectroscopy.

CaCu3Pt4O12: the first perovskite with the B site fully occupied by Pt(4+).

A novel A-site ordered perovskite CaCu(3)Pt(4)O(12) was synthesized under high pressure and high temperature of 12 GPa and 1250 degrees C. CaCu(3)Pt(4)O(12) is the first perovskite in which the B site is fully occupied by Pt(4+). The crystal structure refinement based on the synchrotron powder X-ray diffraction data shows that CaCu(3)Pt(4)O(12) crystallizes in the space group Im3 (cubic) with a lattice constant of a = 7.

Stress measurement under high pressure using Kawai-type multi-anvil apparatus combined with synchrotron radiation.

A system for stress measurement under high pressure has been developed at beamline BL04B1, SPring-8, Japan. A Kawai-type multi-anvil apparatus, SPEED-1500, was used to pressurize polycrystalline KCl to 9.9 GPa in a mechanically anisotropic cell assembly with the KCl sample sandwiched between dense Al(2)O(3) pistons.

A combination of a Drickamer anvil apparatus and monochromatic X-rays for stress and strain measurements under high pressure.

A modified Drickamer anvil apparatus has been developed to combine with monochromatic synchrotron radiation for high-pressure X-ray diffraction and radiography in the GSECARS bending-magnet station, 13-BM-D, at the Advanced Photon Source, Argonne, USA. Using this experimental set-up, deformation experiments can be carried out at pressures in excess of 30 GPa at high temperatures. Differential stresses and total axial strains of polycrystalline platinum and Mg(2)SiO(4) ringwoodite have been measured up to 32 GPa at room temperature using tungsten carbide anvils.

High-pressure creep of serpentine, interseismic deformation, and initiation of subduction.

The supposed low viscosity of serpentine may strongly influence subduction-zone dynamics at all time scales, but until now its role could not be quantified because measurements relevant to intermediate-depth settings were lacking. Deformation experiments on the serpentine antigorite at high pressures and temperatures (1 to 4 gigapascals, 200 degrees to 500 degrees C) showed that the viscosity of serpentine is much lower than that of the major mantle-forming minerals. Regardless of the temperature, low-viscosity serpentinized mantle at the slab surface can localize deformation, impede stress buildup, and limit the downdip propagation of large earthquakes at subduction zones.