Incorporation of rare earth elements in titanite; stabilization of the A2/a dimorph by creation of antiphase boundaries

Hughes, John M.; Bloodaxe, Erich S.; Hanchar, John M.; Foord, Eugene E.

doi:10.2138/am-1997-5-610

Cited by 36 publications

(22 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Concerning titanite crystals, the results reported in Table 2 show that this crystalline phase is the only one able to incorporate trivalent lanthanide ions (Ln 3+ ) in the surface crystallized layer. It appears that Ln 3+ ions are only incorporated into the calcium site of the titanite structure (there is only one type of calcium site in this structure and this site is 7-fold coordinated with oxygen ions [78]) probably because the tetrahedral silicon and the octahedral titanium sites are too small. This result is in accordance with the one published by Higgins et al for natural titanite samples [79].…”

Section: Tablementioning

confidence: 93%

“…As indicated above, tetravalent cerium ions are preferentially incorporated in the baddeleyite (ZrO 2 ) crystals. Divalent europium, that was detected by ESR in the parent glass GEu [13], is also una- Table 4 Sum of the bond valences (Rs Lnj ) calculated for the different lanthanide (Ln) in the calcium site of titanite (coordination j = 7) using the crystallographic structural data of Hughes et al [78] and the R 0 values taken from [71]. V Ln is Ln oxidation state.…”

Section: Tablementioning

confidence: 99%

See 1 more Smart Citation

Glass–ceramic nuclear waste forms obtained by crystallization of SiO2–Al2O3–CaO–ZrO2–TiO2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

Loiseau

Caurant

2010

Journal of Nuclear Materials

View full text Add to dashboard Cite

Section: Tablementioning

confidence: 93%

Section: Tablementioning

confidence: 99%

Glass–ceramic nuclear waste forms obtained by crystallization of SiO2–Al2O3–CaO–ZrO2–TiO2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

Loiseau

Caurant

2010

Journal of Nuclear Materials

View full text Add to dashboard Cite

“…160-1930 ppm) and low REE concentrations (b200 ppm); and sample Tit-E was found to be rich in both, Cr and REE (see Table 1). Chromium and other metals, such as Nb, Ta, V, Mn, Mg, Sn, Al, and Fe, are generally considered to be incorporated at the six-fold coordinated Ti-site (Higgins and Ribbe, 1976;Fleischer, 1978), whereas REEs substitute Ca on its large, sevencoordinated site (Hughes et al, 1997). Charge-balance of trivalent REE within the titanite structure is explained by a coupled substitution with Al and Fe (e.g., Che et al, 2013):…”

Section: Titanite -Catisiomentioning

confidence: 99%

Laser-induced REE3+ photoluminescence of selected accessory minerals — An “advantageous artefact” in Raman spectroscopy

et al. 2015

View full text Add to dashboard Cite

Keywords:Zircon Xenotime Monazite Titanite Laser-induced REE photoluminescence Raman artefact Laser-induced photoluminescence of trivalent rare-earth elements (REEs), which is obtained as analytical artefacts in Raman spectra of selected accessory minerals, was studied. Spectra of natural titanite, monazite-(Ce), xenotime-(Y), and zircon samples from various geological environments were compared with emission spectra of synthetic, flux-grown analogues doped with REEs. The latter is of great importance to identify potentially mistakable bands as either Raman or PL signal, and to assign them to certain REE centres. In the samples investigated, various REE centres are excited selectively using 473, 514, 532, 633, and 785 nm laser excitation. Their assignment was verified by photoluminescence-excitation experiments. Luminescence spectral patterns of zircon and titanite vary in dependence of trace-REE concentrations, hence reflecting geochemical growth conditions. "REE artefacts" in Raman spectra of accessory minerals may be used as fingerprint tool for mineral phaseidentification. The distribution of REE emission-intensities, revealed by hyperspectral mapping, opens up the opportunity to visualise mineral textures, complementary to cathodoluminescence imaging-techniques.

show abstract

“…Both lead to domain wall pinning suppressing an enlargement of small P2 1 /c domains around 500 K and prevent the establishment of long-range order. For that reason the average space group for titanite is C2/c even at room-temperature and locally the P2 1 /c symmetry is still preserved in the crystalline domains [1,[54][55][56].…”

Section: Temperature Induced Phase Transition In Partially Amorphous mentioning

confidence: 99%

Partially amorphous (metamict) titanite: a silicate mineral in a natural radiation induced non-equilibrium phase

Beirau¹

2014

Zeitschrift Für Kristallographie - Crystalline Materials

View full text Add to dashboard Cite

The present review will give a brief overview mainly focused on studies during the past 5 years on the mineral titanite (end-member composition CaTiSiO 5 ) which could incorporate radioactive elements in its crystal structure. Aspects of investigations were the structural damage resulting from the radioactive decay, the thermally induced recrystallization process and the elastic properties of the mineral. During the radiation induced damage process, namely the metamictization, titanite becomes partially amorphous with coexisting defect enriched crystalline and aperiodic regions. Within these crystalline regions a P2 1 /c to C2/c phase transition (∼ at 500 K) occurs. Resulting from radiation induced structural damage, titanite shows elastic properties close to those of titanite glass. During recrystallization on annealing an initial softening of the titanite structure takes place (up to temperature ∼950 K) resulting from the formation of soft interfaces. Thermal annealing at higher temperatures leads to increasing structural order and the hardening of the mineral.

show abstract

Incorporation of rare earth elements in titanite; stabilization of the A2/a dimorph by creation of antiphase boundaries

Cited by 36 publications

References 3 publications

Glass–ceramic nuclear waste forms obtained by crystallization of SiO2–Al2O3–CaO–ZrO2–TiO2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

Glass–ceramic nuclear waste forms obtained by crystallization of SiO2–Al2O3–CaO–ZrO2–TiO2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

Laser-induced REE3+ photoluminescence of selected accessory minerals — An “advantageous artefact” in Raman spectroscopy

Partially amorphous (metamict) titanite: a silicate mineral in a natural radiation induced non-equilibrium phase

Contact Info

Product

Resources

About