Silicates of the rare earth elements

Toropov, N. A.; Galakhov, F. Ya.; Konovalova, S. F.

doi:10.1007/bf00909108

Cited by 32 publications

(26 citation statements)

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“…A similar effect has been documented for rare earth silicates. 48 In all structures the threefold coordination of either NBO or BO (bridging oxygen) results in considerable elongation of Si-O bonds. As first proposed by Begun and Bamberger, 16 the pattern of as PO 2 stretching vibrations can be used to distinguish between metaphosphate structures with condensed and isolated polyhedra.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, POP force constants vary with the change in the coordination of BOs. 48 Since the monoclinic R(PO 3 ) 3 are structures having each oxygen atom shared between two cations, it appears that the increase in POP angles is the main reason for the shift observed. If one assumes that the POP angles in Ga(PO 3 ) 3 are very close to those in Al(PO 3 ) 3 25 (Ic type), then the increase in the POP angle from 128°i n Yb(PO 3 ) 3 44 to 139°in Al(PO 3 ) 3 results in a 35-40 cm 1 upward shift of the as POP bands.…”

Section: Resultsmentioning

confidence: 99%

“…For the sake of comparison, it is worth mentioning that within the isostructural LaPO 4 the asymmetry of PO 4 tetrahedra increases in the La!Eu and Gd!Lu direction. 48 The as POP bands have also been shown to be the most sensitive in the spectra of the vitreous metaphosphates. 19 -21 In all cases the bands discussed shift to lower wavenumbers, suggesting that the POP angles decrease upon crystal!glass transition.…”

Section: Resultsmentioning

confidence: 99%

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Vibrational spectra of R(PO₃)₃ metaphosphates (R = Ga, In, Y, Sm, Gd, Dy)

Ilieva

Kovacheva

Petkov

et al. 2001

J Raman Spectroscopy

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A series of R(PO 3 ) 3 (R = Ga, In, Y, Sm, Gd, Dy) metaphosphate crystals representing four different structural types were prepared and their vibrational spectra recorded. The distribution of internal and external chain modes was obtained taking into account the configuration (site symmetry) of the polyphosphate anions in the corresponding structures. The spectra presented reveal that the P -O − force constants are very sensitive to both the coordination of oxygen atoms and POP bond angles. The spectra of crystalline R(PO 3 ) 3 were compared with data for glassy metaphosphates. It was found that decreasing the size of R(III) cation leads to different structural effects in glasses and crystals of the same composition.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Vibrational spectra of R(PO₃)₃ metaphosphates (R = Ga, In, Y, Sm, Gd, Dy)

Ilieva

Kovacheva

Petkov

et al. 2001

J Raman Spectroscopy

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“…However, the Miller indices of the XRD peaks and the calculated lattice constants (a = 1.123 nm, c = 0.467 nm) of their results were incorrect compared with the present data, for example, compared with the lattice constant of La 9.33 (SiO 4 ) 6 O 2 (a = 0.9714 nm and c = 0.7183 nm). 22) In the second to eighth papers, 15)19) Toropov's group also confirmed two compounds, RE 2 O 3 ·SiO 2 and RE 2 O 3 ·2SiO 2 (RE = Y, Nd, Gd, Dy, Er, Sm, and Yb), discovered by Roy's group. According to this confirmation, the phase diagrams of the RE 2 O 3 SiO 2 quasi-binary system were revised to the same as the data in the Phase Equilibria database 23) (Fig.…”

Section: Identification Of New Compounds and The Phase Diagrams Of Ramentioning

confidence: 92%

Rudimental research progress of rare-earth silicate oxyapatites: their identification as a new compound until discovery of their oxygen ion conductivity

Kobayashi

Sakka

2014

J. Ceram. Soc. Japan

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Rudimental research progress of rare-earth silicate oxyapatites: their identification as a new compound until discovery of their oxygen ion conductivity Kiyoshi KOBAYASHI³ and Yoshio SAKKA Materials Processing Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JapanRudimental research progress of oxyapatite-type rare-earth silicates is reviewed based on the published papers mainly from 1959 to 1993 that have not yet been discussed in detail. The knowledge of oxyapatite-type rare-earth silicates significantly increased during this period. Chemical compounds of rare-earth oxides and silica were discovered around 1960. Because of the complex chemical composition of the oxyapatite phase, the composition was initially considered as 2RE 2 O 3 ·3SiO 2 , which was called orthosilicate. "RE" is the rare-earth elements. Different compositions of 2RE 2 O 3 ·3SiO 2 have been proposed by crystal structure analysis based on the crystal chemistry and the leaping model. With respect to crystal structure analysis, knowledge has gradually improved step-by-step, including the implicit distinction between oxygen-stoichiometric apatite and oxygen-deficient apatite. Based on the published work, the rare-earth silicate oxyapatites are considered to have an apatite-like structure. Initially, application research focused on the optical properties of oxyapatite because rare-earth metals were constituent elements of the crystals, and on the use of oxyapatite as a stabilizer of unwanted radioactive waste produced in nuclear power reactors because oxyapatites can dissolve the actinide elements.

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“…Such scattering losses, however, can be alleviated by infiltrating the film with index-matched polymer, as had been shown for silica nanospheres. 20 Given that the refractive index 21 of Er 2 SiO 5 is 1.825, such a material would have a further advantage of enabling very compact photonic circuits on silica. Furthermore, since the grains are nanometer sized and easily separated, they can be incorporated into small pores of optical nanostructures such as photonic crystals and slot waveguides, 22 whose small sizes require a highgain coefficient.…”

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confidence: 99%

Large-scale fabrication of single-phase Er2SiO5 nanocrystal aggregates using Si nanowires

Suh

Shin

Seo

et al. 2006

Applied Physics Letters

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Single-phase Er 2 SiO 5 nanocrystal aggregates were produced on a large scale using Si nanowire ͑Si-NW͒ arrays as templates. A dense array of Si-NWs was grown by vapor-liquid-solid mechanism using Au catalyst on Si ͑111͒ substrate. Afterwards, ErCl 3 ·6H 2 O dissolved ethanol solution was spin coated and annealed first at 900°C for 4 min in a flowing N 2 /O 2 environment and then at 1200°C in a flowing Ar environment for 3 min. X-ray diffraction, scanning electron microscope, and high-resolution transmission electron microscope measurements indicate that due to the use of Si-NWs, such a short annealing procedure is sufficient to completely transform the Er-coated Si-NWs into a thick, large-area aggregate of pure, single-phase to There is a strong and growing interest in developing Si photonics that can integrate the fast, lossless information carrying capacity of photonics with Si integrated circuit technology to overcome the impending "interconnect bottleneck." 1 In particular, a great effort has been made in developing a Si-based light source, especially a laser, that can overcome the inherent limitation of the indirect band gap of Si. 1,2 Among the many possible ways of obtaining light emission from Si, 3-5 using the rare earth ion Er 3+ as an optical dopant has attracted a special attention because of its ability to provide light at 1.5 m that is compatible not only with optical telecommunication but also with silicon-oninsulator based Si microphotonic devices. 5,6 Furthermore, Er doping has a history of proven success in providing optical gain and lasing when doped into silica fiber amplifiers. 7 The intra-4f transition of Er 3+ that gives rise to the 1.5 m luminescence is parity forbidden and occurs due to the effects of the crystal field surrounding Er 3+ ions. This leads to long luminescence lifetimes and, when doped into an amorphous host such as silica, large inhomogeneous broadening of the atomic luminescence peak that allow for low-noise, broadband amplification capability of EDFAs. Unfortunately, the same qualities can lead to severe limitations for its applicability for Si photonics that requires a large optical gain in a limited wavelength range from a micrometer-sized volume, since the combination of long luminescence lifetimes and a broad luminescence peak results in a low gain cross section at a particular wavelength. Increasing the gain requires a very high Er concentration, but the concentration of optically active Er that can be doped into a host material without clustering is limited, even for an amorphous host such as silica. 8,9 Another way of increasing the gain cross section per wavelength is reducing the inhomogeneous broadening of Er 3+ luminescence by using a crystalline host matrix, but even in that case, controlling the location of Er 3+ ions down to atomic levels is difficult. 10 A rather interesting alternative to Er doping that can overcome these difficulties is to raise the Er concentration so high that a stable, Er rich crystalline phase can form. In particular, crystalline ra...

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Silicates of the rare earth elements

Cited by 32 publications

References 1 publication

Vibrational spectra of R(PO₃)₃ metaphosphates (R = Ga, In, Y, Sm, Gd, Dy)

Vibrational spectra of R(PO₃)₃ metaphosphates (R = Ga, In, Y, Sm, Gd, Dy)

Rudimental research progress of rare-earth silicate oxyapatites: their identification as a new compound until discovery of their oxygen ion conductivity

Large-scale fabrication of single-phase Er2SiO5 nanocrystal aggregates using Si nanowires

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Silicates of the rare earth elements

Cited by 32 publications

References 1 publication

Vibrational spectra of R(PO3)3 metaphosphates (R = Ga, In, Y, Sm, Gd, Dy)

Vibrational spectra of R(PO3)3 metaphosphates (R = Ga, In, Y, Sm, Gd, Dy)

Rudimental research progress of rare-earth silicate oxyapatites: their identification as a new compound until discovery of their oxygen ion conductivity

Large-scale fabrication of single-phase Er2SiO5 nanocrystal aggregates using Si nanowires

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Product

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Vibrational spectra of R(PO₃)₃ metaphosphates (R = Ga, In, Y, Sm, Gd, Dy)

Vibrational spectra of R(PO₃)₃ metaphosphates (R = Ga, In, Y, Sm, Gd, Dy)