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Synthesis and crystal structure of a neodymium borosilicate, Nd3BSi2O10

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aPacific Northwest National Laboratory, Richland, WA 99352, USA
*Correspondence e-mail: jarrod.crum@pnnl.gov

Edited by A. Van der Lee, Université de Montpellier II, France (Received 22 March 2019; accepted 12 April 2019; online 25 April 2019)

A lanthanide borosilicate, trineodymium borosilicate or Nd3BSi2O10, was synthesized using a flux method with LiCl, and its structure was determined from X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA). The structure is composed of layers with [SiO4]4− and [BSiO6]5− anions alternating along the c axis linked by Nd3+ cations between them.

1. Chemical context

Lanthanide borosilicates (i.e. Ln3BSi2O10) crystallize as one of the major phases within the residual glass matrix in some formulations of the glass-ceramic waste form for treatment of raffinate high-level waste (Crum et al., 2012[Crum, J. V., Turo, L., Riley, B., Tang, M. & Kossoy, A. (2012). J. Am. Ceram. Soc. 95, 1297-1303.], 2014[Crum, J., Maio, V., McCloy, J., Scott, C., Riley, B., Benefiel, B., Vienna, J., Archibald, K., Rodriguez, C., Rutledge, V., Zhu, Z., Ryan, J. & Olszta, M. (2014). J. Nucl. Mater. 444, 481-492.], 2016[Crum, J. V., Neeway, J. J., Riley, B. J., Zhu, Z., Olszta, M. J. & Tang, M. (2016). J. Nucl. Mater. 482, 1-11.]). Studies on the crystal chemistry and crystallization mechanism of lanthanide borosilicates are important in understanding the formation and durability of crystalline phases in the glass-ceramic waste forms (Crum et al., 2012[Crum, J. V., Turo, L., Riley, B., Tang, M. & Kossoy, A. (2012). J. Am. Ceram. Soc. 95, 1297-1303.], 2014[Crum, J., Maio, V., McCloy, J., Scott, C., Riley, B., Benefiel, B., Vienna, J., Archibald, K., Rodriguez, C., Rutledge, V., Zhu, Z., Ryan, J. & Olszta, M. (2014). J. Nucl. Mater. 444, 481-492.], 2016[Crum, J. V., Neeway, J. J., Riley, B. J., Zhu, Z., Olszta, M. J. & Tang, M. (2016). J. Nucl. Mater. 482, 1-11.]). In this work, we report the synthesis method and crystal structure of Nd3BSi2O10 solved by powder XRD and EPMA analysis.

Different compositions of lanthanide borosilicates including LnBSiO5 (Ln = La, Ce, Pr, Nd, Sm; McAndrew & Scott, 1955[McAndrew, J. & Scott, T. (1955). Nature, 176, 509-510.]; Neumann et al., 1966[Neumann, H., Bergstøl, S. & Nilssen, B. (1966). Nor. Geo. Tidsskr, 46, 327-334.]; Nekrasov & Nekrasova, 1971[Nekrasov, I. I. & Nekrasova, R. A. (1971). Dokl. Akad. Nauk SSSR, 201, 1202.]; Voronkov & Pyatenko, 1967[Voronkov, A. A. & Pyatenko, Y. A. (1967). Sov. Phys. Cryst. 12, 258-265.]; Burns et al., 1993[Burns, P. C., Hawthorne, F. C., MacDonald, D. J., della Ventura, G. & Parodi, G. C. (1993). Can. Mineral. 31, 147-152.]; Chi et al., 1997[Chi, L., Chen, H., Zhuang, H. & Huang, J. (1997). J. Alloys Compd. 252, L12-L15.]; Shi et al., 1997[Shi, Y., Liang, J. K., Zhang, H., Yang, J. L., Zhuang, W. D. & Rao, G. H. (1997). J. Alloys Compd. 259, 163-169.]), Ln5Si2BO13 (Ln = La, Eu, Gd, Dy; Mazza et al., 2000[Mazza, D., Tribaudino, M., Delmastro, A. & Lebech, B. (2000). J. Solid State Chem. 155, 389-393.]; Yuan et al., 2007[Yuan, J.-L., Zhang, Z.-J., Wang, X.-J., Chen, H.-H., Zhao, J.-T., Zhang, G.-B. & Shi, C.-S. (2007). J. Solid State Chem. 180, 1365-1371.]; Naidu et al., 2010[Naidu, S. A., Varadaraju, U. V. & Raveau, B. (2010). J. Solid State Chem. 183, 1847-1852.]), and Ln3BSi2O10 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb; Chi et al., 1996a[Chi, L., Chen, H., Deng, S., Zhuang, H. & Huang, J. (1996a). Acta Cryst. C52, 2385-2387.],b[Chi, L., Chen, H., Deng, S., Zhuang, H. & Huang, J. (1996b). J. Alloys Compd. 242, 1-5.]; Müller-Bunz & Schleid, 1998[Müller-Bunz, H. & Schleid, T. (1998). Z. Kristallogr. Suppl. 15, 48.]; Chi et al., 1998[Chi, L., Chen, H., Lin, X., Zhuang, H. & Huang, J. (1998). J. Struct. Chem. China, 17, 297-301.], Shvanskii et al., 2000[Shvanskii, E. V., Leonyuk, N. I., Bocelli, G. & Righi, L. (2000). J. Solid State Chem. 154, 312-316.]; Müller-Bunz et al., 2001[Müller-Bunz, H., Grossholz, H. & Schleid, T. (2001). Z. Anorg. Allg. Chem. 627, 1436-1438.]; Bräuchle & Huppertz, 2015[Bräuchle, S. & Huppertz, H. (2015). Z. Naturforsch. Teil B, 70, 929-934.]) have been reported in the literature. LnBSiO5 has the stillwellite structure containing single or mixed lanthanide cations with infinite helical chains composed of six-membered rings formed by two [BO4]5− and one [SiO4]4− tetra­hedral units (Chi et al., 1997[Chi, L., Chen, H., Zhuang, H. & Huang, J. (1997). J. Alloys Compd. 252, L12-L15.]; Burns et al., 1993[Burns, P. C., Hawthorne, F. C., MacDonald, D. J., della Ventura, G. & Parodi, G. C. (1993). Can. Mineral. 31, 147-152.]; Voronkov & Pyatenko, 1967[Voronkov, A. A. & Pyatenko, Y. A. (1967). Sov. Phys. Cryst. 12, 258-265.]; Shi et al., 1997[Shi, Y., Liang, J. K., Zhang, H., Yang, J. L., Zhuang, W. D. & Rao, G. H. (1997). J. Alloys Compd. 259, 163-169.]). Ln5Si2BO13 has an apatite-like structure in which the non-tetra­hedral cation sites are occupied by trivalent rare-earth cations, and B and Si occupy the same tetra­hedral site (Mazza et al., 2000[Mazza, D., Tribaudino, M., Delmastro, A. & Lebech, B. (2000). J. Solid State Chem. 155, 389-393.]). Ln3BSi2O10 contains layers with [SiO4]4− and [BSiO6]5− anions alternating along the c axis linked by trivalent cations between them, and Nd3BSi2O10 in this work is isostructural to previously reported Ln3BSi2O10 compounds (Chi et al., 1996a[Chi, L., Chen, H., Deng, S., Zhuang, H. & Huang, J. (1996a). Acta Cryst. C52, 2385-2387.],b[Chi, L., Chen, H., Deng, S., Zhuang, H. & Huang, J. (1996b). J. Alloys Compd. 242, 1-5.], 1998[Chi, L., Chen, H., Lin, X., Zhuang, H. & Huang, J. (1998). J. Struct. Chem. China, 17, 297-301.], Braeuchle & Huppertz, 2015[Bräuchle, S. & Huppertz, H. (2015). Z. Naturforsch. Teil B, 70, 929-934.]; Shvanskii et al., 2000[Shvanskii, E. V., Leonyuk, N. I., Bocelli, G. & Righi, L. (2000). J. Solid State Chem. 154, 312-316.]; Müller–Bunz et al., 2001[Müller-Bunz, H., Grossholz, H. & Schleid, T. (2001). Z. Anorg. Allg. Chem. 627, 1436-1438.]).

2. Structural commentary

The [BSiO6]5− anion in Nd3BSi2O10 is formed by [Si1O4]4− and [BO3]3− anions sharing an oxygen atom, with an average <Si1—O> distance of 1.613 Å and an average <B—O> distance of 1.466 Å (Fig. 1[link]a), while the [Si2O4]4− ion has an average <Si2—O> distance of 1.590 Å. The [BSi1O6]5− and [Si2O4]4− anions are arranged alternately along the c axis (Fig. 2[link]). The Nd cations occupy the inter­layer sites between the anion units. Nd1 and Nd3 are coordinated by eight oxygen atoms with average <Nd1—O> and <Nd3—O> distances of 2.477 and 2.520 Å, respectively, and Nd2 is coordinated by nine oxygen atoms with an average <Nd2—O> distance of 2.575 Å (Fig. 1[link]b). In our previous paper (Kroll et al., 2019[Kroll, J. O., Crum, J. V., Riley, B. J., Neeway, J. J., Asmussen, R. M. & Liezers, M. (2019). J. Nucl. Mater. 515, 370-381.]), we summarized the crystallographic data from the literature on other Ln3BSi2O10 chemistries (Braeuchle & Huppertz, 2015[Bräuchle, S. & Huppertz, H. (2015). Z. Naturforsch. Teil B, 70, 929-934.]; Chi et al., 1996a[Chi, L., Chen, H., Deng, S., Zhuang, H. & Huang, J. (1996a). Acta Cryst. C52, 2385-2387.],b[Chi, L., Chen, H., Deng, S., Zhuang, H. & Huang, J. (1996b). J. Alloys Compd. 242, 1-5.], 1998[Chi, L., Chen, H., Lin, X., Zhuang, H. & Huang, J. (1998). J. Struct. Chem. China, 17, 297-301.]; Müller–Bunz et al., 2001[Müller-Bunz, H., Grossholz, H. & Schleid, T. (2001). Z. Anorg. Allg. Chem. 627, 1436-1438.]; Shvanskii et al., 2000[Shvanskii, E. V., Leonyuk, N. I., Bocelli, G. & Righi, L. (2000). J. Solid State Chem. 154, 312-316.]) as a function of the ionic crystal radii (rc) for the VIII-coordinated Ln3+ constituent according to Shannon (1976[Shannon, R. D. (1976). Acta Cryst. A32, 751-767.]) to create predictive models for the unit-cell parameters (i.e., a, b, and c), cell volume, and cell density. The measured values of a (9.7889 Å), b (7.1077 Å), c (23.0893 Å), cell volume (1606.5 Å3), and density (5.4551 Mg m−3) all fit reasonably well with the values calculated using the rc for Nd (1.109 Å), i.e., a (9.799 Å), b (7.111 Å), c (23.095 Å), cell volume (1608.4 Å3), and cell density (5.49 Mg/m3). Detailed atomic coordinates, bond lengths, and angles are given in Tables S1 and S2 in the supporting information.

[Figure 1]
Figure 1
(a) Structure of the BSiO6 anion and (b) coordination of oxygen atoms around Nd cations (Nd1, Nd2, and Nd3).
[Figure 2]
Figure 2
Crystal structure of Nd3BSi2O10 showing alternating [BSiO6]5− and [SiO4]4− anions along the c axis with Nd cations between them.

3. Synthesis and crystallization

Nd3BSi2O10 was synthesized by a LiCl flux method; more details are provided elsewhere (Kroll et al., 2019[Kroll, J. O., Crum, J. V., Riley, B. J., Neeway, J. J., Asmussen, R. M. & Liezers, M. (2019). J. Nucl. Mater. 515, 370-381.]). Powdered B2O3 was placed into a Pt–10%Rh crucible, melted at 1273 K in air to dehydrate fully and quenched on an Inconel plate. Appropriate amounts of Nd2O3, SiO2, and B2O3 were mixed in an agate mortar and pestle. LiCl was dried at 378 K for several hours and mixed with oxides in a 1:1 ratio by mass in a DiamoniteTM mortar and pestle. Mixed powder was placed into a fused quartz tube, covered with a quartz lid, heated to 1173 K at 5 K min−1, held for 24 h at 1173 K, and then cooled down to room temperature at 1 K min−1. The Nd3BSi2O10 was recovered from the LiCl through vacuum filtration with several rinsing steps using deionized water and a Büchner funnel. The recovered heat-treated powder was ground finer in the mortar and pestle and pressed into a 20 mm diameter pellet using a cold press with 110 MPa. The pellet was sintered at 1373 K. The heating condition included ramping up at 2 K min−1 to 1373 K, dwelling for 4 h, and cooling to room temperature at 2 K min−1. The heat-treated pellet, which was blue–violet in color, was ground for XRD and EPMA. Two EPMA measurements were performed on the sample to verify the composition of the crystal and showed that it closely matches the calculated value (Fig. 3[link]).

[Figure 3]
Figure 3
Comparison of oxide mass% between targeted and measured Nd3BSi2O10 from EPMA measurement.

4. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1[link]. A Rietveld plot is shown in Fig. 4[link]. The structure of Nd3BSi2O10 was determined using Rietveld refinement on the initial model with a similar chemistry and structure using TOPAS (version 4.2; Bruker, 2009[Bruker (2009). TOPAS., Bruker AXS, Karlsruhe, Germany.]). Based on the fitting of peak positions and profile of experimental XRD patterns to a reference pattern, Ce3BSi2O10 (ICSD 94423) was used as a starting model. The Ce atoms in ICSD 94423 were replaced with Nd atoms, and all the atomic positions for Nd, B, Si, and O were refined. The profile of the model was refined from 14.5° to avoid a hump around 13.5° in the fitting of the background resulting from an instrumental artifact. The displacement parameters (Beq) were not refined and fixed to 1 Å2 to avoid divergence and unreasonable error values. In addition, parameters for unit cell, scale factors, microstructure effects, and preferred orientation with spherical harmonic function (Järvinen, 1993[Järvinen, M. (1993). J. Appl. Cryst. 26, 525-531.]) were refined, and the background was fitted with a Chebychev polynomial.

Table 1
Experimental details

Crystal data
Chemical formula Nd3BSi2O10
Mr 659.7
Crystal system, space group Orthorhombic, Pbca
Temperature (K) 295
a, b, c (Å) 9.78891 (17), 7.10774 (12), 23.0893 (4)
V3) 1606.49 (5)
Z 8
Radiation type Cu Kα, λ = 1.54188 Å
Specimen shape, size (mm) Flat sheet, 25 × 25
 
Data collection
Diffractometer Bruker D8 Advance
Specimen mounting Packed powder pellet
Data collection mode Reflection
Scan method Step
2θ values (°) 2θmin = 14.5 2θmax = 90 2θstep = 0.014
 
Refinement
R factors and goodness of fit Rp = 0.03, Rwp = 0.04, Rexp = 0.011, RBragg = 0.013, χ2 = 13.250
No. of parameters 82
Computer programs: XRD Commander (Kienle et al., 2003[Kienle, M. & Jacob, M. (2003). DIFFRAC plus XRD Commander. Bruker AXS GmbH, Karlsruhe, Germany.]), TOPAS (Bruker, 2009[Bruker (2009). TOPAS., Bruker AXS, Karlsruhe, Germany.]), VESTA (Momma & Izumi, 2011[Momma, K. & Izumi, F. (2011). J. Appl. Cryst. 44, 1272-1276.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).
[Figure 4]
Figure 4
Observed, calculated, and difference XRD profiles of Nd3BSi2O10.

Supporting information


Computing details top

Data collection: XRD Commander (Kienle et al., 2003); cell refinement: TOPAS (Bruker, 2009); program(s) used to solve structure: TOPAS (Bruker, 2009); program(s) used to refine structure: TOPAS (Bruker, 2009); molecular graphics: VESTA (Momma & Izumi, 2011); software used to prepare material for publication: publCIF (Westrip, 2010).

Trineodymium borosilicate top
Crystal data top
Nd3BSi2O10Z = 8
Mr = 659.7Dx = 5.455 Mg m3
Orthorhombic, PbcaCu Kα radiation, λ = 1.54188 Å
a = 9.78891 (17) ÅT = 295 K
b = 7.10774 (12) Åblue_violet
c = 23.0893 (4) Åflat_sheet, 25 × 25 mm
V = 1606.49 (5) Å3
Data collection top
Bruker D8 Advance
diffractometer
Data collection mode: reflection
Radiation source: sealed X-ray tubeScan method: step
Specimen mounting: packed powder pellet2θmin = 14.5°, 2θmax = 90°, 2θstep = 0.014°
Refinement top
Rp = 0.0382 parameters
Rwp = 0.04Weighting scheme based on measured s.u.'s
Rexp = 0.011(Δ/σ)max = 0.011
RBragg = 0.013Background function: Chebychev
5738 data pointsPreferred orientation correction: spherical harmonic
Profile function: pseudo-Voigt
Special details top

Refinement. background fitted from 14.5 degree to avoid a hump from instrumental artifact

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzBiso*/Beq
Nd10.4909 (2)0.3621 (3)0.42810 (6)1
Nd20.1338 (2)0.3296 (4)0.33652 (7)1
Nd30.2655 (2)0.0934 (3)0.18257 (7)1
B10.249 (4)0.387 (7)0.9703 (13)1
Si10.3810 (10)0.3516 (16)0.0787 (3)1
Si20.4381 (9)0.3240 (17)0.2814 (4)1
O10.2558 (17)0.254 (3)0.9191 (7)1
O20.1165 (18)0.399 (3)0.9903 (7)1
O30.3697 (19)0.348 (3)0.0088 (6)1
O40.4525 (17)0.170 (3)0.1055 (7)1
O50.2286 (15)0.346 (3)0.1083 (7)1
O60.4662 (17)0.537 (3)0.0938 (8)1
O70.6028 (18)0.293 (2)0.2773 (7)1
O80.4151 (15)0.369 (2)0.2120 (7)1
O90.3903 (18)0.466 (2)0.3239 (7)1
O100.3481 (15)0.138 (3)0.2880 (6)1
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
???????
Geometric parameters (Å, º) top
Nd1—O1i2.454 (17)Nd3—O7vi2.325 (16)
Nd1—O2ii2.460 (19)B1—O21.38 (4)
Nd1—O2iii2.265 (17)Si1—O31.618 (16)
Nd1—O4iv2.39 (2)Si1—O41.59 (2)
Nd1—O6v2.40 (2)Si1—O51.641 (18)
Nd2—O1i2.327 (17)Si1—O61.60 (2)
Nd2—O8vi2.432 (15)Si2—O71.63 (2)
Nd2—O10vii2.47 (2)Si2—O81.649 (19)
Nd3—Nd3viii3.567 (3)Si2—O91.483 (19)
Nd3—Nd3vii3.567 (3)Si2—O101.60 (2)
Nd3—O5viii2.457 (19)
O1i—Nd1—O2ii83.2 (6)O3—Si1—O6105.4 (11)
O1i—Nd1—O2iii128.2 (6)O4—Si1—O5102.6 (11)
O1i—Nd1—O4iv119.9 (6)O4—Si1—O6110.7 (11)
O1i—Nd1—O6v79.8 (6)O5—Si1—O6113.8 (11)
O2ii—Nd1—O2iii70.5 (6)O7—Si2—O896.0 (9)
O2ii—Nd1—O4iv69.9 (6)O7—Si2—O9116.3 (11)
O2ii—Nd1—O6v149.5 (6)O7—Si2—O10116.1 (11)
O2iii—Nd1—O4iv92.2 (7)O8—Si2—O9117.9 (11)
O2iii—Nd1—O6v101.0 (7)O8—Si2—O10100.3 (9)
O4iv—Nd1—O6v140.6 (6)O9—Si2—O10109.0 (10)
O1i—Nd2—O8vi149.1 (6)Nd1ix—O1—Nd2ix117.7 (7)
O1i—Nd2—O10vii124.2 (6)Nd1x—O2—Nd1xi109.5 (7)
O8vi—Nd2—O10vii75.6 (5)Nd1x—O2—B1104 (2)
Nd3viii—Nd3—Nd3vii170.24 (8)Nd1xi—O2—B1141.4 (17)
Nd3viii—Nd3—O5viii44.7 (4)Nd1v—O4—Si1135.9 (10)
Nd3viii—Nd3—O7vi123.3 (4)Nd3vii—O5—Si1104.6 (9)
Nd3vii—Nd3—O5viii135.7 (4)Nd1iv—O6—Si1147.0 (11)
Nd3vii—Nd3—O7vi48.2 (4)Nd3xii—O7—Si2137.5 (9)
O5viii—Nd3—O7vi137.0 (5)Nd2xii—O8—Si2107.8 (8)
O3—Si1—O4113.9 (11)Nd2viii—O10—Si2137.7 (9)
O3—Si1—O5110.7 (10)
Symmetry codes: (i) x, y+1/2, z1/2; (ii) x+1/2, y+1, z1/2; (iii) x+1/2, y, z+3/2; (iv) x+1, y+1/2, z+1/2; (v) x+1, y1/2, z+1/2; (vi) x1/2, y, z+1/2; (vii) x+1/2, y+1/2, z; (viii) x+1/2, y1/2, z; (ix) x, y+1/2, z+1/2; (x) x+1/2, y+1, z+1/2; (xi) x1/2, y, z+3/2; (xii) x+1/2, y, z+1/2.
 

Funding information

The authors acknowledge financial support from the US Department of Energy Office of Nuclear Energy (DOE-NE). The Pacific Northwest National Laboratory is operated by Battelle under Contract Number DE-AC05–76RL01830.

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