Phosphate tungsten bronze series: crystallographic and structural properties of low-dimensional conductors

Roussel, Pascal; Pérez, Olivier; Labbé, Ph.

doi:10.1107/s0108768101009685

Cited by 59 publications

(46 citation statements)

References 72 publications

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“…This results in the electrical compensation due to both electron and hole pockets left in the FS and the high mobility of the carriers originating from them, leading to the enhanced Nernst effect with a magnitude as large as those reported in heavy fermion compounds. We also suggest, that since several other members of the monophosphate bronzes family undergo the Peierls transition above 300 K [35], the search of large Nernst effect at room temperature in these materials appears promising.…”

Section: Fig 2 Region Of the (H0l)mentioning

confidence: 89%

Giant Nernst effect in the incommensurate charge density wave state ofP4W12O44

et al. 2016

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We report the study of Nernst effect in quasi-low dimensional tungsten bronze P4W12O44 showing a sequence of Peierls instabilities. We demonstrate that both condensation of the electronic carriers in the CDW state and the existence of high-mobility electrons and holes originating from the small pockets remaining in the incompletely nested Fermi surface give rise to a Nernst effect of a magnitude similar to that observed in heavy fermion compounds. [10,11]. In these cases, the N values were above those expected within a simple diffusive picture of electronic transport.The charge density wave (CDW) state of a quasi-low dimensional solid shows, to some extent, similarities with dilute anisotropic metals. The Peierls instability is associated to the nesting of the Fermi surface (FS) accompanied by condensation of electronic carriers. While in an ideal 1D material the Fermi surface is expected to be completely destroyed, the nesting in 2D systems is not perfect and small FS pockets containing high mobility carriers can remain [12,13]. Despite these strongly favorable conditions, the Nernst effect was explored only in a few of the CDW materials as NbSe 2 [14], where the Peierls instability involves the nesting of the minor part of the Fermi Surface. In addition to that, in NbSe 2 , the positive signal due to superconducting fluctuations dominates over the component driven by quasiparticles as soon as the temperature approaches T c , similarly to the features found in cuprate superconductors [15,16], where the relevance of CDW formation was recently emphasized [17].The promising features standing behind the Peierls instability motivated us to explore the Nernst effect in a purely CDW material with strong FS nesting and absence of a superconducting transition. For this study, we have chosen P 4 W 12 O 44 , which belongs to the monophosphate bronze family of quasi-2D metals known to exhibit Peierls instabilities. In P 4 W 12 O 44 , a sequence of three CDW transitions lead to the nesting of the major part of the high temperature Fermi surface [18][19][20] with several pockets left at low temperatures. Those were found to contain light free electronic carriers with the mobility high enough to allow observation of Shubnikov de Haas (SdH) [21] and de Haas-van Alpen [22] oscillations in this material. This predisposes P 4 W 12 O 44 to exhibit large Nernst coefficient.To characterize the CDW transition, we have performed a high resolution thermal X-ray diffuse scattering experiment on a single crystal of P 4 W 12 O 44 showing an adequate crystalline quality (plate-like single crystals with typical size of 5 mm x 1 mm x 0.5 mm were grown by chemical vapor transport [23]). The experiment was performed at beamline Crystal of synchrotron Soleil, using monochromated radiation with wavelength λ = 0.50718 A and beam size of 200 µm x 200 µm. Sample was cooled in a stream of cold He gas. Frames were collected above T P 1 = 120 K (temperature expected for the first transition), in between T P 1 and T P 2 = 62 K (temperature expected fo...

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Section: Fig 2 Region Of the (H0l)mentioning

confidence: 89%

Giant Nernst effect in the incommensurate charge density wave state ofP4W12O44

et al. 2016

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“…During the formation of the W 4 O 18 chain, the tungsten octahedra suffer a distortion to reduce the strain. 17,21 This distortion is mainly a rotation around the vertical axis.…”

Section: Crystallographic Structurementioning

confidence: 99%

“…Two successive step layers run following a herringbone pattern along the c direction 21 and they are related by a 2 1 -fold axis. The unit-cell sizes are aϭ5.285 Å, b ϭ6.569 Å, and cϭ17.351 Å.…”

Section: Crystallographic Structurementioning

confidence: 99%

Fermi-surface analysis of a quasi-two-dimensional monophosphate tungsten bronze

et al. 2004

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The P 4 W 8 O 32 compound is a member of the low-dimensional monophosphate tungsten bronzes family whose reduced dimensionality induces electronic instabilities such as charge-density waves ͑CDWs͒. We report here the direct mapping of the Fermi surface ͑FS͒ of this compound at room temperature using synchrotronradiation angle-resolved photoemission. The recorded FS images confirm the superimposition of three nested sheets, as proposed by the hidden-nesting model. We found two well defined parallel stripes along the ⌫Y direction as well as a crosslike feature. Moreover, the small FS splitting predicted by ab initio calculations was distinguished in the experimental data. To extract quantitative information on the CDW phase transitions, the values of the nesting vectors were also determined from the FS topology. The obtained values were in excellent agreement with existing tight-binding calculations, although the accord was even better with the recently published ab initio theoretical predictions.

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“…35 These have similar properties to oxides bronzes such as Na x WO 3 (see Oxides: Solid-state Chemistry) and are strongly colored metals or semiconductors. They are formed by inserting planes of orthophosphate or diphosphate anions into the ReO 3 type WO 3 lattice, analogous to the formation of shear phases in the reduction of this structure (see Defects in Solids).…”

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confidence: 97%

Phosphates: Solid‐State Chemistry

Attfield

2005

Encyclopedia of Inorganic Chemistry

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Phosphates contain oxyanions of phosphorus(V). The most common anion is the orthophosphate group PO 4 3− , which is found in many solid phosphates including hydrated and acid phosphate salts. Oligomeric polyphosphate chains P n O 3 n +1 ( n +2)− up to n = 6 and cyclophosphate rings P n O 3 n n − up to n = 12 are also observed, and a unique cage ultraphosphate anion P 8 O 23 6− is found in the Na 3 FeP 8 O 23 structure. Polymeric phosphate anions include the infinite chain catenaphosphate anion (PO 3 − ) ∞ and the ultraphosphate networks found in CaP 4 O 11 and the lanthanide MP 5 O 14 structures. Many compound anions and neutral frameworks such as silicophosphates, aluminophosphates, and molybdenum phosphates also exist. Phosphate species are characterized through PO stretching and bending vibrations in infrared and Raman spectroscopies, and by 31 P NMR. Phosphate structures are generally rigid, resistant to chemical attack, and (when anhydrous) insoluble and thermally stable. Some phosphate crystals have important physical properties such as ferrolectricity in KH 2 PO 4 (potassium dihydrogenphosphate, KDP). Diffusion of extra‐framework ions leads to potential uses of solid phosphates as ion exchangers and conductors, for example, NASICON based on NaZr 2 (PO 4 ) 3 , and as cathode materials for lithium batteries. Vanadium phosphates are important selective oxidation catalysts. Large pore phosphates in which molecules can be adsorbed and undergo acid‐catalyzed reactions have been intensively studied. These materials are crystalline microporous solids such as aluminophosphates, or lamellar structures, typically based on α‐Zr(HPO 4 ) 2 ·H 2 O that can be pillared. This area of interest has led to the synthesis of many new organically templated metal phosphates in recent years, usually through hydrothermal reactions. Hydrated and acid orthophosphates can also be prepared in solution, and anhydrous phosphates are synthesized by direct high‐temperature reactions and from phosphate‐rich melts or fluxes. Slow cooling of melts is used to grow crystals, and quenching can result in many stable phosphate glasses. Phosphate anions do not absorb significantly in the UV‐visible region and so solid phosphates can also find use as optical materials such as phosphors, nonlinear crystals, for example, KTiOPO 4 , and lasers. Solid phosphates constitute many minerals, notably Apatites which are also found in living organisms as rigid components such as bones and teeth. Synthetic calcium phosphate biomaterials are used for bone implants.

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Phosphate tungsten bronze series: crystallographic and structural properties of low-dimensional conductors

Cited by 59 publications

References 72 publications

Giant Nernst effect in the incommensurate charge density wave state ofP4W12O44

Giant Nernst effect in the incommensurate charge density wave state ofP4W12O44

Fermi-surface analysis of a quasi-two-dimensional monophosphate tungsten bronze

Phosphates: Solid‐State Chemistry

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