Belt-type Apparatus Research Articles

A novel ferrimagnetic irido-cuprate: IrSr 2GdCu 2O 8

We have performed an investigation of the structural, microstructural and magnetic properties of the new compound IrSr 2GdCu 2O 8. The sample was prepared under high temperature (∼1393 K) and high-pressure conditions (∼60 Kbars) in a Belt type apparatus. X-ray diffraction (XRD) analysis shows that this irido-cuprate is isostructural with the corresponding Ru-1212 phase. Structurally, this material shows an interesting hierarchy of ordering phenomena, whose observation actually depends on the technique used to analyze the material: from a “simple” cell a p× a p×3 a p which is supported by XRD, through a “diagonal” one, ∼ 2 a p × 2 a p × 3 a p as seen by SAED, to a microdomain texture of this last one cell supported by HREM. A ferrimagnetic Ir IV–Gd III spin ordering is observed below 15 K. The iridium oxidation state seems to be +4.

A new belt-type apparatus for neutron-based rheological measurements at gigapascal pressures

We have developed a new solid-media apparatus for performing rheological investigations at multi-gigapascal pressures. The pressure cell consists of a simple belt design and fits in a modified 250 tonne Paris–Edinburgh press. Elastic strains are measured by neutron diffraction, on the ENGIN-X experimental station at ISIS. Stresses are estimated from the measured strains in combination with published values of the elastic moduli. As an exemplair of the method, we present data from initial deformation experiments on pyrope garnet at 1.5 GPa and 873 K. Data collection times are as short as 60 min and the elastic strain resolution is better than 10−4. We anticipate, however, that by interrupted testing, strain rates as low as 10−9/s, or lower, will be measurable.

TiC–diamond composite disk-heater cell assembly to generate temperature of 2000 °C in a large-volume belt-type high-pressure apparatus at 10 GPa

A TiC–diamond composite was prepared for the heater of a large-volume belt type high-pressure apparatus. Graphite has conventionally been used for the heater in high-pressure studies, but it cannot be used at pressure higher than 10 GPa and above 1500 °C because of the problem associated with the graphite-to-diamond phase transformation. New TiC–diamond heater overcomes this problem and achieves stable temperature generation by using a belt-type high-pressure apparatus. The composite was fabricated by heat-treatment of a mixture of diamond and TiC0.8 with nonstoichiometric composition at ambient pressure. By optimizing the preparation conditions, we obtained TiC–diamond composites that exhibited mechanical and electrical properties suitable for a heater material without any volatile component such as resin. Since reported conventional TiC–diamond composite heaters include epoxy resin as binder, volatile components arise from decomposition of the resin at high temperature preventing stable high-pressure/high-temperature experiment above 2000 °C. Attainment of reproducible temperature-generation efficiency in the present heater makes it possible to perform stable experiments at high temperature and pressure, i.e., in the region of 2000 °C and 10 GPa.

Crystal structures ofα-quartz homeotypes boron phosphate and boron arsenate: structure-property relationships

AbstractThe structures of single crystals of theα-quartz homeotypes boron phosphate and boron arsenate prepared under high-pressure, high-temperature conditions in a belt-type apparatus were determined by X-ray diffraction. Both structures are more distorted with respect to theβ-quartz structure type thanα-quartz itself with average tetrahedral tilt anglesδof 19.7° and 24.6° for BPO4and BAsO4, respectively. The structure of BAsO4is one of the most highly distorted found amongα-quartz homeotypes. It is shown that for the knownα-quartz homeotypes, the density, which can be related to the frequency constant for piezoelectric resonators, scales with the intertetrahedral bridging angleθ.

High Pressure Synthesis and Structure Refinement of LiTiSi2O6.

AbstractFor Abstract see ChemInform Abstract in Full Text.

High-pressure synthesis and crystal structures of B 2Sr 3(Y,Sr) 2Cu 3O 12 and B 2Sr 3(Ho,Sr) 2Cu 3O 12

Two new layered oxyborates B 2Sr 3.2Y 1.8Cu 3O 12 and B 2Sr 3.11Ho 1.89Cu 3O 12 have been synthesized at 6 GPa using a belt-type apparatus. These compounds could be described as intergrowth between B-1201 and B-1212 phases. The crystal structure of B 2Sr 3.11Ho 1.89Cu 3O 12 has been determined using single crystal X-ray data. It was refined to R1( I>2 σ( I))=0.0456, wR2( all data )=0.1044 with F 2 data. B 2Sr 3.2Y 1.8Cu 3O 12 and B 2Sr 3.11Ho 1.89Cu 3O 12 crystallize in the space group P4/mmm (no. 123), Z=1 with a=3.852(1) Å, c=17.770(6) Å and a=3.8516(4) Å, c=17.764(2) Å, respectively. A weak superstructure with a s= a√2, b s= b√2, c s= c was deduced from an electron diffraction pattern for B 2Sr 3.11Ho 1.89Cu 3O 12 probably due to local ordering of the triangular BO 3 groups although such ordering was not revealed from single crystal X-ray data.

Mn3Sb: A New L12‐Type Intermetallic Compound Synthesized under High‐Pressure.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Mn 3Sb: a new L1 2-type intermetallic compound synthesized under high-pressure

A new intermetallic compound, Mn 3Sb, has been synthesized by direct reaction of elemental components at 6.2 GPa and 1000 °C for 30 min using a belt-type high-pressure apparatus. The compound crystallizes into a cubic structure with the space group Pm-3 m, namely the L1 2-type (Cu 3Au-type) structure. The structure was refined by the Rietveld analysis of the powder X-ray diffraction data and the lattice constant was determined to be a=0.40017(2) nm. The compound exhibits metallic conductivity and weak ferromagnetism.

Crystal structures of CCa 2CuO 5 and CSr 1.9Ca 1.1Cu 2O 7 refined from single crystal data

Single crystals were grown for new layered oxycarbonates CCa 2CuO 5 and CSr 1.9Ca 1.1Cu 2O 7 at 6 GPa using a belt-type apparatus. Their crystal structures were determined using single crystal X-ray diffraction data with R1( wR2)=0.0294(0.0659) and 0.0199(0.0457) for CCa 2CuO 5 and CSr 1.9Ca 1.1Cu 2O 7, respectively. These phases crystallize in the space group P4/mmm (No. 123), Z=1 with a=3.8157(1) Å, c=7.1426(3) Å for CCa 2CuO 5 and a=3.8753(1) Å, c=10.6765(5) Å for CSr 1.9Ca 1.1Cu 2O 7. In contrast to CSr 2CuO 5, no ordering in the orientation of the triangular CO 3 groups was revealed in CCa 2CuO 5 and CSr 1.9Ca 1.1Cu 2O 7.

Heater cell for materials synthesis and crystal growth in the large volume high pressure apparatus at 10 GPa

To realize materials synthesis and crystal growth in a large volume of high pressure apparatus in the region of 10 GPa, a heater cell was developed for a belt-type high pressure apparatus with a bore diameter of 32 mm. The cell consists of a cylindrical electrode made of TiC powders located between a pair of graphite heaters with a disk shape. High temperature of 1500 °C at nominal pressure of 9.7 GPa (9.35 GPa corrected) was successfully generated for 1 h using the cell. Synthesis and growth of stishovite was performed at high pressure and high temperature conditions based on their calibrations. Experimental results suggest that the materials synthesis and crystal growth above 10 GPa can be realized in a large volume of belt-type apparatus using the heater cell.

Effect of pressure on the microstructure of α-Fe/Sm2(Fe, Si)17Cx nanocomposite magnets

The effect of pressure on the microstructure of α-Fe/Sm2(Fe, Si)17Cx nanocomposite magnets has been studied by annealing amorphous Sm8Fe85Si2C5 alloy under pressures up to 6 GPa at 923 K. The high-pressure experiments were carried out in a belt-type apparatus. Experimental results show that, with increasing pressure from normal pressure to 6 GPa, the grain size of the α-Fe and Sm2(Fe, Si)17Cx phases in the α-Fe/Sm2(Fe, Si)17Cx nanocomposites decreases, from 30.6 to 6.4 nm for the former and from 28.7 to 5.8 nm for the latter. The volume fraction of Sm2(Fe, Si)17Cx increases as pressure increases. The α-Fe/Sm2(Fe, Si)17Cx nanocomposite magnets prepared under 4 GPa have a significant increase in both coercivity and remanent magnetization as compared to those prepared under normal pressure.

Crystallization process of an amorphous Sm 8Fe 85Si 2C 5 alloy under high pressure

The crystallization process of amorphous Sm 8Fe 85Si 2C 5 alloy under a pressure of 4 GPa at a temperature of 923 K has been investigated. The high-pressure experiments were carried out in a belt-type pressure apparatus. Experimental results show that the crystalline phases in the annealed alloy consist of α-Fe phase and Sm 2(Fe, Si) 17C x . The grain size of the α-Fe phase and Sm 2(Fe, Si) 17C x in the alloy annealed for 20 min is 5.2 and 4.2 nm, respectively; and it increases slowly with annealing time. The volume fraction of both the α-Fe phase and Sm 2(Fe, Si) 17C x increases with increasing the annealing time. As the annealing time increases to 60 min, an α-Fe/Sm 2(Fe, Si) 17C x nanocomposite microstructure with a fine grain size, 8.8 nm for the α-Fe phase and 7.6 nm for the Sm 2(Fe, Si) 17C x , forms in the annealed alloy. The mechanism of crystallization of the amorphous Sm 8Fe 85Si 2C 5 alloy under high pressure is discussed. The α-Fe/Sm 2(Fe, Si) 17C x nanocomposite magnets prepared under 4 GPa have, compared with nanocomposite magnets prepared under normal pressure, an increase in both coercivity and remanent magnetization.

Structural Properties of GeSe2 at High Pressures

Crystalline and glassy GeSe2 have been subjected to pressures up to 7.7 GPa and temperatures up to 1100°C using a high-pressure belt-type apparatus. Two high-pressure crystalline polymorphs of GeSe2 have been synthesized. The crystal structure of the tetragonal form of GeSe2 prepared at 3.0 GPa and 500°C, with space group I-42d and a=5.7307(4) and c=9.691(1), was determined by means of powder X-ray diffraction data. The structure consists of GeSe4 tetrahedra that share corners in a three-dimensional network and has a considerably higher density than the two-dimensional structure of ambient-pressure GeSe2 consisting of both edge- and corner-sharing tetrahedra. The IR and Raman spectra of tetragonal GeSe2 are discussed in relation to the structure of GeSe2 glass. An orthorhombic polymorph of GeSe2 was formed during quenching from 7.7 GPa and 500°C. Amorphous GeSe2 compressed at 250–300°C was observed to partly crystallize at 3.0 and 7.7 GPa.

Formation of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy under high pressure

The formation of nanocrystalline Fe73.5 Cu1Nb3Si13.5 B9 alloy by annealing an amorphous Fe73.5Cu1Nb3Si13.5B9 alloy at a temperature of 823 K under pressures in the range of 1–5 GPa is investigated by using X-ray diffraction, electron diffraction, and transmission electron microscopy. The high pressure experiments are carried out in belt-type pressure apparatus. Experimental results show that the initial crystalline phase in these annealed alloys is a-Fe solid solution (named a-Fe phase below), and high pressure has a great influence on the crystallization process of the a-Fe phase. The grain size of the a-Fe phase decreases with the increase of pressure (P). The volume fraction of the a-Fe phase increases with increasing the pressure as the pressure is below 2 GPa, and then decreases (Pδ2 GPa). The mechanism for the effects of the high pressure on the crystallization process of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy is discussed

Microstructure and magnetic properties of Sm2(Fe, Si)17Cx/α-Fe nanocomposite magnets prepared under high pressure

We present microstructure and magnetic properties of Sm2(Fe, Si)17Cx/α-Fe nanocomposite magnets prepared under a pressure of 4 GPa at a temperature of 923 K. A high-pressure experiment was carried out in a belt-type pressure apparatus. Analyses of x-ray diffraction and transmission electron microscopy show that the nanocomposite magnets have a grain size of 6–8 nm, which provides a strong exchange coupling between hard and soft magnetic phases. As a result, the magnets have, compared with nanocomposite magnets prepared under normal pressure, a significant increase in both coercivity, from 132 to 500 kA/m, and remanent magnetization, from 0.68 to 0.83Ms.

Magnetoresistance of Sr1−xKxBiO3: a second-family of bismuth-oxide-based superconductors

The superconducting Sr1−xKxBiO3samples with x = 0.45 – 0.6 were synthesized by the high-pressure-high-temperature technique in a belt type apparatus (2 GPa, 700 °C, 1 h, Pt capsules) with stoichiometric mixtures of Sr2Bi2O5, Bi2O3and KO2as described earlier.1The X-ray diffraction results appear as a single perovskite-like phase. The superconductivity occurs at Tc∼ 12 K in the A. C. susceptibility measurement. The onset (zero resistivity) temperature of superconductivity in resistivity measurement of the investigated sample was\(T_{conset} = 12.5{\text{ }}K(T_{czero} = 10.2{\text{ }}K)\). The transition temperature region was a little bit broad and a shoulder was present about 11.3 K indicating probably the existence of crystallites of different K content. The particularly interesting point is that the resistance begins to reappear at T < 6 K at zero magnetic field. As the external magnetic field is applied, the reentrant resistance disappears and superconductivity is recovered until the applied magnetic field becomes higher than 0.65 Tesla. The superconductivity for T < 6 K is destroyed for the higher magnetic field. The Tconsetdecreases as the magnetic field increases like in the BCS type superconductors. The transition region becomes broader under the magnetic field, which indicate a kind of vortex transition as in the case of high Tccuprates.

Crystal structure and high pressure behaviour of the quartz-type phase of phosphorus oxynitride PON

Phosphorus oxynitride PON is isoelectronic with SiO 2 and both exhibit cristobalite- and quartz-type phases. The α-quartz phase of PON was prepared by submitting the β-cristobalite phase to 4.5 GPa and 750°C in a belt type apparatus. The structure at ambient was refined using time-of-flight neutron powder diffraction data on a quenched sample. The structure (trigonal, P3 221, a=4.757(4), c=5.2460(2) Å, Z=3) is essentially the same as that of α-quartz SiO 2. The atomic positions and temperature factors of phosphorus, oxygen and nitrogen were obtained. Oxygen and nitrogen are completely disordered over the 6(c) sites. The behaviour of α-quartz-type PON under pressure was determined by angle dispersive X-ray powder diffraction in a diamond anvil cell up to 48 GPa. The cell parameters were measured as a function of pressure. A transition to an α-quartz II phase occurs at close to 20 GPa; the main change is a small, but distinct increase in the c/ a ratio. Progressive and irreversible amorphisation of PON was observed above 30 GPa, and no diffraction lines could be detected above 42 GPa. For both PON and SiO 2, the α-quartz-type phases undergo phase changes under pressure to quartz II phases followed by amorphisation. This pressure study reinforces the parallel behaviour of the two compounds.

Influence of pressures on the crystallization process of an amorphous Fe73.5Cu1Nb3Si13.5B9 alloy

Amorphous Fe73.5Cu1Nb3Si13.5B9 alloys, prepared by a melt-spinning technique, were annealed at a temperature of 823 K under pressures in the range of 1–5 GPa and ambient pressure. The high pressure experiments were carried out in a belt-type pressure apparatus. The microstructure of the annealed alloys has been investigated by x-ray diffraction, electron diffraction, and transmission electron microscopy. Experimental results show that the initial crystalline phase in these annealed alloys is α-Fe solid solution (named as α-Fe phase below), and high pressure has a great influence on the crystallization process of the α-Fe phase. The grain size of the α-Fe phase decreases with the increase of pressure (P). The volume fraction of the α-Fe phase increases with increasing the pressure as the pressure is below 2 GPa, and then decreases (P&amp;gt;2 GPa). The mechanism for the effects of the high pressure on the crystallization process of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy and latent applications of high-pressure annealing amorphous Fe73.5Cu1Nb3Si13.5B9 alloy have been discussed.

Electronic absorption by Ti 3+ ions and electron delocalization in synthetic blue rutile

Polarized absorption spectra, σ and π, in the spectral range 30000–400 cm−1 (3.71–0.05 eV) were obtained on crystal slabs // [001] of deep blue rutile at various temperatures from 88 to 773 K. The rutile crystals were grown in Pt-capsules from carefully dried 99.999% TiO2 rutile powder at 50 kbar/1500 °C using graphite heating cells in a belt-type apparatus. Impurities were below the detection limits of the electron microprobe (about 0.005 wt% for elements with Z≥13). The spectra are characterized by an unpolarized absorption edge at 24300 cm−1, two weak and relatively narrow (Δν1/2≈3500–4000 cm−1), slightly σ-polarized bands ν1 at 23500 cm−1 and ν2 at 18500 cm−1, and a complex, strong band system in the NIR (near infra red) with sharp weak peaks in the region of the OH stretching fundamentals superimposed on the NIR system in the σ-spectra. The NIR band system and the UV edge produce an absorption minimum in both spectra, σ and π, at 21000 cm−1, i.e. in the blue, which explains the colour of the crystals. Bands ν1 and ν2 are assigned to dd transitions to the Jahn-Teller split upper Eg state of octahedral Ti3+. The NIR band system can be fitted as a sum of three components. Two of them are partly π-polarized, nearly Gaussian bands, both with large half widths 6000–7000 cm−1, ν3 at 12000 cm–1 and the most intense ν4 at 6500 cm−1. The third NIR band ν5 of a mixed Lorentz-Gaussian shape with a maximum at 3000 cm−1 forms a shoulder on the low-energy wing of ν4. Energy positions, half band widths and temperature behaviour of these bands are consistent with a small polaron type of Ti3+Ti4+ charge transfer (CT). Polarization dependence of CT bands can be explained on the basis of the structural model of defect rutile by Bursill and Blanchin (1983) involving interstitial titanium. Two OH bands at 3322 and 3279 cm−1 in σ-spectra show different stability during annealing, indicating two different positions of proton in the rutile structure, one of them probably connected with Ti3+ impurity. Total water concentration in blue rutile determined by IR spectroscopy is 0.10 wt-% OH. The EPR spectra measured in the temperature interval 20–295 K show the presence of an electron centre at temperatures above 100 K and Ti3+ ions in more than one structural position, but predominantly in compressed interstitial octahedral sites, at lower temperatures. These results are in good agreement with the conclusions based on the electronic absorption data.

High Pressure Synthesis and Structure Refinement of Yttrium-Zinc intermetallic Compound Y2Zn17.

Single crystal of yttrium-zinc intermetallic compound Y2Zn17 have been synthesized from the elements by means of high-pressure and high-temperature methods in a modified Belt type apparatus (h-BN capsule, 3. 5GPa, 1700°C, and subsequent release of high pressure). Y2Zn17 crystallizes in the hexagonal system with lattice constants a=8. 9709 (8) A, c=13. 1386 (8) A, c/a=1. 4646, space group R 3 m (No. 166), and Z=3. Final residuals after refinement against F2 were R1=0. 0270, ωR2=0. 0612 and S=1. 239 for 23 parameters and all 237 unique data. Y2Zn17 adopts Th2Zn17-type structure.