Crystal chemistry of the monazite structure

Clavier, Nicolas; Podor, Renaud; Dacheux, Nicolas

doi:10.1016/j.jeurceramsoc.2010.12.019

Cited by 344 publications

(261 citation statements)

References 329 publications

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“…Upon compression phosphates with smaller lanthanides, like LuPO 4 and YbPO 4 [35] transform from zircon to scheelite, but those closer to the zircon-monazite stability border accommodate stresses transforming from zircon to monazite, e.g. TbPO 4 and ErPO 4 [13,35], which is much more flexible structure than scheelite [36]. An analogous behavior is expected for the vanadates with the only difference that at ambient conditions the frontier between zircon and monazite is located between Ce and La.…”

Section: Resultsmentioning

confidence: 81%

In situhigh-pressure synchrotron x-ray diffraction study of CeVO4and TbVO4up to 50 GPa

et al. 2011

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Room temperature angle-dispersive x-ray diffraction measurements on zircon-type TbVO 4 and CeVO 4 were performed in a diamond-anvil cell up to 50 GPa using neon as pressure-transmitting medium. In TbVO 4 we found at 6.4 GPa evidence of a non-reversible pressure-induced structural phase transition from zircon to a scheelite-type structure. A second transition to an M-fergusonite-type structure was found at 33.9 GPa, which is reversible. Zircon-type CeVO 4 exhibits two pressureinduced transitions. First an irreversible transition to a monazite-type structure at 5.6GPa and second at 14.7 GPa a reversible transition to an orthorhombic structure. No additional phase transitions or evidences of chemical decomposition are found in the experiments. The equations of state and axial compressibility for the different phases are also determined. Finally, the sequence of structural transitions and the compressibilities are discussed in comparison with other orhtovanadates and the influence of non-hydrostaticity commented.

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Section: Resultsmentioning

confidence: 81%

In situhigh-pressure synchrotron x-ray diffraction study of CeVO4and TbVO4up to 50 GPa

et al. 2011

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“…The idealized chemical formula of monazite is LnPO 4 , where Ln represents the trivalent lanthanide ions from La to Gd (Ni et al, 1995;Clavier et al, 2011). Monazite crystallizes in the monoclinic space group P2 1 /n with four formula units per unit cell.…”

Section: Introductionmentioning

confidence: 99%

Evidence for Lattice Strain and Non-ideal Behavior in the (La1−xEux)PO4 Solid Solution from X-ray Diffraction and Vibrational Spectroscopy

2016

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The monazite-type solid solution of LaPO 4 and EuPO 4 has been studied by X-ray diffraction, infrared (IR) and Raman spectroscopic techniques. A substantial excess molar volume has been derived from the X-ray data, and the Raman and IR spectra show band broadening typical for mixing of cations of different size on the cation sublattice. The IR spectra were interpreted by the autocorrelation method and the excess autocorrelation parameter corr ex shows clear deviation from ideal solution behavior, similar to the observed broadening of the Raman bands. The results can be interpreted in terms of local lattice strains resulting from the ion size effects of substitution of La 3+ by Eu 3+ , and correlate very well with calorimetric measurements of the excess enthalpy that was previously measured.

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“…The structural arrangement of monazite is based on the nine-fold coordination of the Pb and the four-fold coordination of Cr [9].…”

Section: Introductionmentioning

confidence: 99%

Tuning the band gap of PbCrO4 through high-pressure: Evidence of wide-to-narrow semiconductor transitions

Errandonea

Bandiello

Segura

et al. 2014

Journal of Alloys and Compounds

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Abstract:The electronic transport properties and optical properties of lead(II) chromate (PbCrO 4 ) have been studied at high pressure by means of resistivity, Hall-effect, and optical-absorption measurements. Band-structure first-principle calculations have been also performed. We found that the low-pressure phase is a direct band-gap semiconductor (Eg = 2.3 eV) that shows a high resistivity. At 3.5 GPa, associated to a structural phase transition, a band-gap collapse takes place, becoming Eg = 1.8 eV. At the same pressure the resistivity suddenly decreases due to an increase of the carrier concentration. In the HP phase, PbCrO 4 behaves as an n-type semiconductor, with a donor level probably associated to the formation of oxygen vacancies. At 15 GPa a second phase transition occurs to a phase with Eg = 1.2 eV. In this phase, the resistivity increases as pressure does probably due to the self-compensation of donor levels and the augmentation of the scattering of electrons with ionized impurities. In the three phases the band gap red shifts under compression. At 20 GPa, Eg reaches a value of 0.8 eV, behaving PbCrO 4 as a narrow-gap semiconductor.

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Crystal chemistry of the monazite structure

Cited by 344 publications

References 329 publications

In situhigh-pressure synchrotron x-ray diffraction study of CeVO4and TbVO4up to 50 GPa

In situhigh-pressure synchrotron x-ray diffraction study of CeVO4and TbVO4up to 50 GPa

Evidence for Lattice Strain and Non-ideal Behavior in the (La1−xEux)PO4 Solid Solution from X-ray Diffraction and Vibrational Spectroscopy

Tuning the band gap of PbCrO4 through high-pressure: Evidence of wide-to-narrow semiconductor transitions

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