New rare earth langbeinite phosphosilicates KBaREEZrP2SiO12 (REE: La, Nd, Sm, Eu, Gd, Dy) for lanthanide comprising nuclear waste storage

Article abstract of DOI:10.1016/j.jallcom.2015.10.088

In contrast to the existing cubic langbeinite phosphates and sulphates, orthorhombic langbeinite phosphosilicates of the chemical formula KBaYMP₂SiO₁₂ (M: Zr, Sn), KBaREEZrP₂SiO₁₂ (REE: La, Nd, Sm, Eu, Gd, Dy) and the wasteform KBaY_0.6La_0.1Nd_0.1Sm_0.1Eu_0.1ZrP₂SiO₁₂ have been synthesized by solution method. Powder X-ray diffraction analysis affirmed that the compounds were phase pure and crystallized in an orthorhombic structure with P2₁2₁2₁ space group. Spectral analysis of the wasteform revealed the phase stability, thermal stability and chemical durability of the langbeinite structure. Chemical durability of the powder wasteform has been studied by a dynamic Soxhlet test. Elemental analysis of the leachates showed that the normalized mass losses of barium, zirconium and silicon were in the order of 10^-3-10^-2 g/m², 10^-5-10^-4 g/m² and 10^-2-10^-1 g/m² respectively. Normalized mass losses of lanthanides, potassium and phosphorous were found to be below the instrumental detection limits.

Full text of DOI:10.1016/j.jallcom.2015.10.088

Accepted Manuscript
New rare earth langbeinite phosphosilicates KBaREEZrP SiO (REE: La, Nd, Sm,
2
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Eu, Gd, Dy) for lanthanide comprising nuclear waste storage
Sathasivam Pratheep Kumar, Buvaneswari Gopal
PII:
S0925-8388(15)31344-X
10.1016/j.jallcom.2015.10.088
JALCOM 35643
DOI:
Reference:
To appear in: Journal of Alloys and Compounds
Received Date: 11 June 2015
Revised Date: 22 September 2015
Accepted Date: 12 October 2015
Please cite this article as: S.P. Kumar, B. Gopal, New rare earth langbeinite phosphosilicates
KBaREEZrP SiO (REE: La, Nd, Sm, Eu, Gd, Dy) for lanthanide comprising nuclear waste storage,
2
12
Journal of Alloys and Compounds (2015), doi: 10.1016/j.jallcom.2015.10.088.
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ACCEPTED MANUSCRIPT
New rare earth langbeinite phosphosilicates KBaREEZrP2SiO12 (REE: La, Nd, Sm,
Eu, Gd, Dy) for lanthanide comprising nuclear waste storage
Sathasivam Pratheep Kumar a, b, * and Buvaneswari Gopala
aMaterials Chemistry Division, School of Advanced Sciences, VIT University, Vellore-
632 014, Tamil Nadu, India.
bNational Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047,
Japan.
Abstract
In contrast to the existing cubic langbeinite phosphates and sulphates, orthorhombic
langbeinite phosphosilicates of the chemical formula KBaYMP2SiO12 (M: Zr, Sn),
KBaREEZrP2SiO12 (REE: La, Nd, Sm, Eu, Gd, Dy) and the wasteform
KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12 have been synthesized by solution method.
Powder X-ray diffraction analysis affirmed that the compounds were phase pure and
crystallized in an orthorhombic structure with P212121 space group. Spectral analysis of
the wasteform revealed the phase stability, thermal stability and chemical durability of
the langbeinite structure. Chemical durability of the powder wasteform has been studied
by a dynamic Soxhlet test. Elemental analysis of the leachates showed that the
normalized mass losses of barium, zirconium and silicon were in the order of 10-3-10-2
g/m2, 10-5-10-4 g/m2 and 10-2-10-1 g/m2 respectively. Normalized mass losses of
lanthanides, potassium and phosphorous were found to be below the instrumental
detection limits.
Key words: Langbeinite phosphosilicate, X-ray diffraction, Infrared spectra, Thermal
analysis, Chemical durability

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*Corresponding author
E-mail: pratheepvit@gmail.com
Present address: National Institute for Materials Science, 1-2-1 Sengen, Tsukuba,
Ibaraki 305-0047, Japan. Fax: +81-29-859-2401; Tel: +81-29-859-2000 ex. 3795;
1. Introduction
Encapsulation of high level nuclear waste (HLW), which is generated from the spent
nuclear fuel reprocessing, into a thermodynamically stable and radiation resistant solid
matrix is an important issue for the department of nuclear energy. In this contest, many
host matrices related to glass, glass-ceramic, synroc and phosphate ceramics have been
investigated in the past three decades [1-7]. Among the studied host ceramic matrices,
single phasic phosphates have paid much attention due to their thermodynamic, radiation
and chemical stabilities [7, 8]. Similarly, silicate based materials like aluminosilicate [9],
zircon [10] and britholite [11] have also been found to be a candidate materials for the
immobilization of minor actinides and lanthanides.
Compounds of langbeinite structure are of particular interest due to their
interesting properties such as optical, magnetic, ferroelectric and phase transitions [12-
15]. The crystal structure of langbeinite (A2B2(XO4)3) is built with the nine coordinated
sites (A cations), octahedral sites (B cations) and tetrahedral sites (XO4 oxyanion). The
three dimensional (3D) network structure is closely related to the nasicon-type and
garnet-type structures [16]. Studies reveal that langbeinite compounds are exist in cubic
and orthorhombic structure with the space group of P213 and P212121 respectively [17]. A
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large number of ionic substitutions into the 3D structure have been reported by many
authors [18-33].
Langbeinite phosphates such as KCsFeZrP3O12 [18], KSrFe2(PO4)3 [19],
KSrSc2(PO4)3:Ce3+/Eu2+/Tb3+ [12], K2MIII (MVIO4)(PO4)2; MIII: Fe, Sc; MVI: Mo, W
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[13], K2GdZr(PO4)3 [20], K2AlM(PO4)3; M: Sn, Ti [21, 22], K2YHf(PO4)3 [23],
K2FeZr(PO4)3 [24], K2LnZr(PO4)3; Ln: Ce-Yb, Y [25], Na2MTi(PO4)3; M: Fe, Cr [26],
K2M0.5Ti1.5(PO4)3; M: Mn, Co [27], K2MTi(PO4)3; M: Er, Yb or Y [28], KBaM2(PO4)3;
M: Fe, Cr [29], Cs2Ni2(MoO4)3 [30], Rb3Yb2(PO4)3 [31], Rb2YbTi(PO4)3 [32],
Cs1+xLnxZr2-x(PO4)3; Ln: Sm-Lu [33] have been found to be crystallize in a high
temperature cubic structure with P213 space group. However, few sulphates and
vanadates (M+ Mn2(SO4)3; M+ = K, NH4, Tl and MBaCr2(VO4)3; M = Li, Na or Ag) were
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identified as low temperature orthorhombic phases with P212121 space group [17, 34].
Langbeinite structure is considered for the fixation of high level nuclear waste
because of (i) the large cavity which forms due to the interconnection of octahedral and
tetrahedral groups is capable of accommodating bigger ions [30, 33], (ii) the structural
stability towards a wide range of ionic substitutions [35] and (iii) the leach resistance
under dynamic conditions [36]. Although, phosphate, silicate, titanate and
phosphosilicate based wasteforms with different structures are available in the literature,
a wasteform of langbeinite phosphosilicate has not been reported. Therefore, the current
work aims to fabricate a wasteform with langbeinite structure to immobilize selected
lanthanides along with the zirconium ion. Hence, we have synthesized new langbeinite
phosphosilicates of the chemical formula KBaYMP2SiO12 (M: Zr, Sn),
KBaREEZrP2SiO12 (REE: La, Nd, Sm, Eu, Gd, Dy) and the wasteform
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KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12. The phase stability and chemical durability of the
wasteform have been investigated and the results are discussed in this paper.
2. Experimental Section
2.1. Materials
(COOK)2.H2O (99.5%, CDH, India), BaNO3 (99.5%, S.D.Fine Chemicals, India),
REE2O3 [REE = La, Ce, Nd, Sm, Eu, Gd, Dy and Y] (99.9%, Sigma Aldrich, India),
ZrOCl2.8H2O (Loba Chemie, India), SnCl4.5H2O (98%, Sigma Aldrich, India), H3PO4
(88%, S.D.Fine Chemicals, India) and Si(OC2H5)4 (98%, Sigma Aldrich, India).
2.2. Synthesis of KBaYMP2SiO12 (M: Zr, Sn), KBaREEZrP2SiO12 (REE: La, Nd,
Sm, Eu, Gd, Dy) and the wasteform KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12
Stoichiometric amount of potassium chloride, zirconyl chloride/ stannic chloride and
phosphoric acid were dissolved separately in each 10 ml of deionized water. Yttrium
oxide and tetraethyl orthosilicate (TEOS) were dissolved in 10 ml of 1:1 nitric acid and
10 ml of ethanol respectively. The solutions were mixed in the following order with
constant stirring on a magnetic stirrer. First potassium chloride solution was added into
the zirconyl chloride/tin chloride solution. To this mixture barium nitrate followed by
yttrium nitrate solutions were added. To the above metal nitrate mixture, phosphoric acid
and TEOS solutions were added drop wise one after the other. The resultant
homogeneous precipitated solution was further stirred for 20 minutes and dried at 80 ºC
in a hot air over for 24 h. The dried precursor was calcined at 600 °C, 900 °C, 1100 °C
and 1200 °C for 24 h at each stage with intermittent grinding to attain the homogeneous
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product. Similar procedure was followed to synthesis KBaREEZrP2SiO12 (REE: La, Nd,
Sm, Eu, Gd, Dy) and the wasteform KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12. Rare earth
oxides were dissolved in 10 ml of 1:1 nitric acid and used.
2.3. Dissolution test
Dissolution test of the powder wasteform KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12 has been
carried out by a Soxhlet method for a period of one month as described in our previous
studies [37, 38]. To brief, the 1200 ºC sintered pellets were crushed in an agate mortar
and sieved in 85-100 mesh brass sieves to collect uniform sized powders. 1 g of washed
and dried powder was used for the test. The leachant (deionized water) was heated to boil
at 90 ±5 °C, vaporized and condensed through the condenser to fall the droplets on the
sample. The flow rate of fresh leachant was maintained at the rate of 1.0 L/day. 20 ml of
the leachate was collected after every 24 h interval for elemental analysis and the same
volume of fresh leachant was replaced to maintain the constant volume. The collected
leachate was analyzed by Inductively Coupled Plasma-Optical Emission Spectroscopy
(ICP-OES). The BET surface area of the wasteform was found to be 0.4677 m2/g. From
the ICP-OES results, normalized elemental mass loss (expressed in g/m2) and the
corresponding normalized leach rate (expressed in g/m2/day) of molybdenum were
determined by considering the following equation [39]
Where Ci = analyzed concentration of ith component in g/ml, V = volume of the leachant
in ml, S = surface area of the sample, t = time in days and fi = mass fraction of the ith
component in the original sample (unitless).
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2.4. Characterization
The synthesized products were characterized by powder X-ray diffraction (XRD) method
(CuKα, Bruker, D8 Advanced) at room temperature. The unit cell parameters and cell
volume were calculated by least square refinement method. Fourier Transformed Infrared
Spectra (FTIR) was recorded by JASCO, FT-IR/4100 spectrometer using KBr pellet
technique in the frequency range of 400-4000 cm-1. Scanning Electron Microscopic
(SEM) images were recorded using FEI Quanta FEG 200 attached with EDS. Thermal
analysis was performed on TA instruments Model SDT Q600 in the temperature range
RT – 1000 °C. Surface area for the powder sample was measured using BET technique
on Micromeritics, ASAP 2020 V3.00H. Inductively Coupled Plasma Optical Emission
Spectroscopic (ICP-OES) analysis was performed using Perkin Elmer, Optima 5300 DV
ICP-OES.
3. Results and Discussion
3.1. Spectral analysis of KBaYZrP2SiO12 and KBaYSnP2SiO12
3.1.1. Powder XRD
The powder XRD patterns of KBaYZrP2SiO12 (KYZP) and KBaYSnP2SiO12 (KYSP)
recorded at room temperature are shown in Fig. 1. The XRD patterns of both compounds
were indexed based on the orthorhombic langbeinite K2Ca2S3O12 (ICDD card No: 74-
0404) and identified as single phasic. Generally, phosphates and sulphates of langbeinites
were crystallized in cubic structure whereas vanadates of the formula MBaCr2(VO4)3 (M
= Li, Na or Ag) (rV = 0.355 Å (td)) preferred an orthorhombic symmetry [34]. The
evolution of orthorhombic structure can be explained based on the size of ions substituted
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in the tetrahedral site. Survey of langbeinite compounds indicates that most of the
sulphates (rS = 0.12 Å (td)) and phosphates (rP = 0.17 Å (td)) crystallize in cubic structure
[40, 25]. Comparing the room temperature structures of K2Mg2(SO4)3 and K2Ca2(SO4)3, it
is noted that the presence of bigger Ca2+ ion results in symmetry reduction. In the current
systems 1/3rd of ‘PO4’ tetrahedra were replaced by a bigger ‘SiO4’ tetrahedra (rSi = 0.26 Å
(td)) [41]. Further, crystallographically, Speer and Salje demonstrated that the driving
force behind the structural transformation is a slight rotation of SO4 tetrahedra [17]. Thus,
it is presumed that the average size effect of the tetrahedra influences the structure and
resulted in an orthorhombic symmetry for the compounds.
In order to find the effect of zirconium ion replacement with tin ion, the unit cell
parameters and cell volumes were calculated by least square refinement method. The
corresponding values are compared in Table 1. The cell parameter values indicate that
‘a’, ‘b’ and the cell volume of KYSP were decreased slightly compared to the phase
KYZP. This indicate that the fraction of MO6 octahedra shrinks by replacing the bigger
ZrO6 octahedra (rZr = 0.72 Å) with the smaller SnO6 octahedra (rSn = 0.69 Å) ion.
3.1.2. FT-IR and SEM study
The FT-IR spectra of both compounds are shown in Fig. 2. Identification of the
vibrational modes of (P-O) and (Si-O) was found to be difficult due to the similar
absorption frequency of ‘PO4’ and ‘SiO4’ tetrahedral groups [42]. For the compound
KYZP, the asymmetric and stretching vibrational modes of (P-O) were observed at 1054
cm-1, 1014 cm-1 and 919 cm-1 respectively. However, the stretching bands for (Si-O) were
not identified, which could be due to the overlapping of both (P-O) and (Si-O) vibrational
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bands. The asymmetric and symmetric bending vibrational modes of (P-O) were noticed
at 553 cm-1, 580 cm-1 and 497 cm-1 respectively. In the case of KYSP compound, the
stretching and bending vibrational modes of (P-O) were observed at 1220 cm-1,1087 cm-1
and 577 cm-1, 524 cm-1 respectively. Similarly, the stretching and bending vibrational
modes of (Si-O) were noticed at 1006 cm-1 and 787 cm-1, 458 cm-1 respectively. Overall, a
comparative FT-IR spectra of KYZP and KYSP show that the substitution of ‘Sn’ ion for
‘Zr’ ion lead to broadening of vibrational bands and a shift in their positions.
Surface morphology of the phases was observed by scanning electron microscope.
A significant difference in the particles shape was noticed between the samples KYZP
and KYSP. Figure 4 shows the lower and higher magnified SEM images of KYZP and
KYSP. In the case of KYZP, appearance of uniformly distributed hexagonal particles was
noticed. When zirconium ion was replaced with tin ion, the particles were transformed
from hexagonal shape to rod shape. Furthermore, the particles size in both the
compounds was found to be in the range of nanoscale. The diameter of hexagonal shaped
particles (KYZP) and rod shaped particles (KYSP) was in the range of 39-120 nm and
35-145 nm respectively. The morphological change indicates that the small variation in
ionic radii (rZr = 0.72 Å; rSn = 0.69 Å) could make a large difference in the surface
structures.
3.2. Lanthanide incorporation
Since zirconium is one of the major radionuclide in most of the HLW, the ‘Zr’ containing
phase KBaYZrP2SiO12 has been chosen for the incorporation of lanthanides. The yttrium
ion was replaced by the rare earth ions to obtain KBaREE3+ZrP2SiO12 where REE3+ = La,
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Nd, Sm, Eu, Gd and Dy compounds. The powder XRD patterns (Fig. 4) were indexed
based on the orthorhombic langbeinite K2Ca2S3O12 (ICDD No: 74-0404) and identified
them as phase pure. For comparison, the powder XRD pattern of KYZP is given at the
base in Fig. 4. Compared to the powder XRD pattern of KYZP (Fig. 4a), lanthanide
substituted phases (Figs. 4b to 4g) show peak shifts towards lower angle due to the
replacement of yttrium ion by rare earth ions. The calculated unit cell parameters and cell
volume of the compounds are given in Table 2. Though the cell parameters show
difference in their values due to the substitution of various rare earth cations, the size
effect was not gradual for the compounds. To understand this complex behavior of lattice
parameter changes, a detailed structural investigation of these compounds is needed.
Since the FT-IR spectra of KBaREE3+ZrP2SiO12 where REE3+ = La, Nd, Sm, Eu,
Gd and Dy compounds were identical to the FT-IR spectrum of KYZP, the characteristic
stretching and bending vibrational mode values of PO4 and SiO4 tetrahedra are
summarized in Table 3. The spectral data show variations in peak positions with the
replacement of yttrium ion by the rare earth ions.
3.3. Phase stability and chemical durability of the wasteform
3.3.1. Powder XRD and FT-IR
The wasteform KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12 has been synthesized as described
in section 2.2 to incorporate lanthanide ions along with zirconium into langbeinite
structure. Powder XRD pattern of the wasteform (Fig. 6b) confirmed the single phasic
orthorhombic structure similar to the parent compound KYZP (Fig. 6a). A simultaneous
fixation of La, Nd, Sm and Eu ions by the partial replacement of yttrium ion led to appear
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few extra reflections (Fig. 6b) in the powder XRD pattern of the wasteform. However,
the extra reflections were also attributed to the orthorhombic langbeinite structure (ICDD
card No: 74-0404). When Gd and Dy ions were tried to incorporate in the wasteform by
further reducing the yttrium percentage, a segregation of the phase was noticed.
FT-IR spectra of the wasteform and KYZP are compared in Figure 7. The
wasteform show stretching and bending vibrational modes of (P-O) and (Si-O) similar to
the parent phase KYZP. However, a significant reduction in the intensity of vibrational
frequencies was observed in the wasteform due to the incorporation of selected
lanthanides in place of yttrium ion.
3.3.2. TGA and SEM-EDX
Thermal stability of the wasteform has been tested as it is an important parameter to
assess the wasteform. Figure 8 shows the thermogravimetric profile analyzed between
room temperature and 1000 °C. The absence of any weight loss in the TGA curve proves
that the wasteform is stable up to 1000 °C, which is acceptable for practical applications.
Scanning electron micrographs of the wasteform are shown in Fig. 8. The lower
magnified image (Fig. 8a) shows that the smaller particles were deposited on a larger
particle. Also, it was found that the larger particles were agglomerated each other. Figure
8b indicates that the size of deposited smaller particles were in the range of 100-250 nm.
This size difference of the particles could be due to the substitution of rare earth ions. To
confirm the effect of lanthanide ions addition, the SEM image of the wasteform was
compared with the SEM image of KYZP (Figs. 3a and 3b). This comparison reveals that
the particles were transformed from well distributed hexagonal particles into an
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agglomerated hexagonal particles with the substitution of La, Nd, Sm and Eu for yttrium
ion in the compound KYZP. The presence of incorporated elements in the wasteform was
confirmed by the EDX spectrum (Fig. 8c).
3.3.3. Chemical durability
Chemical durability of the wasteform was studied as described in section 2.3. Analysis of
the leachates by ICP-OES showed only the leaching of Ba, Zr and Si ions. The
concentration of all other ions was found to be below the instrumental detection limit.
The instrumental detection limit values for K, Y, La, Nd, Sm, Eu and P are 0.001, 0.004,
0.01, 0.09, 0.04, 0.002 and 0.08 ppm respectively. Normalized mass loss and leach rate
of the elements Ba, Zr and Si were calculated as described in section 2.3 and the values
are given in Table 4.
The normalized mass loss of barium increased linearly with time whereas it was
almost plateaued for zirconium after 15 days of the experiment. The normalized mass
loss of silicon was only observed for initial 7 days and it was below the instrumental
detection limit during later days. Figure 9 shows the leach rates of barium and zirconium
from the wasteform. The leach rate of Ba, Zr and Si was found to be in the order of 10-4
g/m2/d, 10-6-10-5 g/m2/d and 10-4-10-2 g/m2/d respectively. The negligible leaching of
potassium could be attributed to the encapsulation of monovalent ion in the closed cavity
of the three dimensional structure. However, the leach resistance of rare earth elements
and phosphorous could be due to the differences in the metal-oxide bond strength,
solubility and mobility of the ions. It is worth mention that the leaching behavior of
lanthanides is similar to our recently investigated monazite and apatite wasteforms [37,
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38]. Further, the leach rate of phosphorus from langbeinite structure is several order
lower (BDL) than the apatite structure (LRP: 10-4-10-3 g/m2/d) [38].
Phase stability of the wasteform after leach test was investigated by the powder
XRD. Figure 10 shows the powder XRD patterns of the wasteform before and after leach
test. From the results, it was noticed that the wasteform is stable ever after one month
continuous exposure with water. However, the crystallinity of the wasteform after the test
was affected as it can be seen from the x-ray diffraction pattern (Fig. 10b). Thus, the
preliminary results on the phase stability towards ionic substitution, thermal stability and
chemical durability study indicate that langbeinite structure could be considered as a
suitable candidate for the fixation of lanthanide comprising high level nuclear waste.
4. Conclusions
In summary, we have synthesized a series of novel langbeinite phosphosilicates and the
wasteform by solution method and characterized them by several spectroscopic analysis.
All the compounds were identified as single phasic orthorhombic structure with P212121
space group. Electron micrographs of KBaYZrP2SiO12 and KBaYSnP2SiO12 displayed a
remarkable difference in the particles shape. A distributed crystalline hexagonal and rod
shaped particles were obtained for the compounds KBaYZrP2SiO12 and KBaYSnP2SiO12
respectively. Dissolution test of the langbeinite wasteform resulted negligible leaching of
lanthanides. However, leach rates of barium, zirconium and silicon elements were found
to be in the order of 10-4 g/m2/d, 10-6-10-5 g/m2/d and 10-4-10-2 g/m2/d respectively.
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Acknowledgement
The authors thank VIT University for providing all required facilities to carry out the
experiments.
References
[1] Q. Liao, F. Wang, K. Chen, S. Pan, H. Zhu, M. Lu, J. Qin, J. Mol. Struct. 1092 (2015)
187-191.
[2] S. Gin, A. Abdelouas, L.J. Criscenti, W.L. Ebert, K. Ferrand, T. Geisler, M.T.
Harrison, Y. Inagaki, S. Mitsui, K.T. Mueller, J.C. Marra, C.G. Pantano, E.M. Pierce,
J.V. Ryan, J.M. Schofield, C.I. Steefel, J.D. Vienna, Mater. Today 16 (2013) 243-248.
[3] P. Sengupta, J. Hazard. Mater. 235-236 (2012) 17-28.
[4] P. Loiseau, D. Caurant, J. Nucl. Mater. 402 (2010) 38-54.
[5] R.R. Madhavan, A.S. Gandhi, K.V.G. Kutty, J. Nucl. Mater. 420 (2012) 554-558.
[6] Y. Zhang, M.W.A. Stewart, H. Li, M.L. Carter, E.R. Vance, S. Moricca, J. Nucl.
Mater. 395 (2009) 69-74.
[7] E.H. Oelkers, J.M. Montel, Elements 4 (2008) 113-116.
[8] N. Dacheux, N. Clavier, A.C. Robisson, O. Terra, F. Audubert, J.E. Lartigue, C. Guy,
C.R. Chim. 7 (2004) 1141-1152.
[9] M.D. Kaminski, C.J. Mertz, M. Ferrandon, N.L. Dietz, G. Sandi, J. Nucl. Mater. 392
(2009) 510-518.
[10] Y. Ding, X. Lu, H. Tu, X. Shu, H. Dan, S. Zhang, T. Duan, J. Eur. Ceram. Soc. 35
(2015) 2153-2161.
[11] C. Chairat, E.H. Oelkers, J. Schott, J.E. Lartigue, J. Nucl. Mater. 354 (2006) 14-27.
13

ACCEPTED MANUSCRIPT
[12] M. Jiao, W. Lv, W. Lu, Q. Zhao, B. Shao, H. You, Dalton Trans. 44 (2015) 4080-
4087.
[13] N.S. Slobodyanik, K.V. Terebilenko, I.V. Ogorodnyk, I.V. Zatovsky, M. Seredyuk,
V.N. Baumer, P. Gutlich, Inorg. Chem. 51 (2012) 1380-1385.
[14] G. Guelylah, G. Madariaga, W. Morgenroth, M.I. Aroyo, T. Breczewski, E.H.
Bocanegra, Acta Crystallogr. Sect. B: Struct. Sci. B56 (2000) 921-935.
[15] G. Nalini, T.N. G. Row, Chem. Mater. 14 (2002) 4729-4735.
[16] Y. Piffard, A. Verbaere, M. Kinoshita, J. Solid State Chem. 71 (1987) 121-130.
[17] D. Speer, E. Salje, Phys. Chem. Miner. 13 (1986) 17-24.
[18] S.P. Kumar, B. Gopal, J. Alloy Compd. 615 (2014) 419-423.
[19] M. Hidouri, M.L. Lopez, C. Pico, A. Wattiaux, M.B. Amara, J. Mol. Struct. 1030
(2012) 145-148.
[20] S. Chawla, Ravishanker, Rajkumar, A.F. Khan, R.K. Kotnala, J. Lumin. 136 (2013)
328-333.
[21] H.Y. Li, D. Zhao, Acta Crystallogr. Sect. E: Struct. Rep. E67 (2011) i56.
[22] D. Zhao, H. Zhang, S.P. Huang, W.L. Zhang, S.L. Yang,W.D. Cheng, J. Alloy
Compd. 477 (2009) 795-799.
[23] I.V. Ogorodnyk, I.V. Zatovsky, N.S. Slobodyanik, Acta Crystallogr. Sect. E: Struct.
Rep. E65 (2009) i63-i64.
[24] A.I. Orlova, I.G. Trubach, V.S. Kurazhkovskaya, P. Pertierra, M.A. Salvado, S.G.
Granda, S.A. Khainakov, J.R. Garcıa, J. Solid State Chem. 173 (2003) 314-318.
[25] I.G. Trubach, A.I. Beskrovny, A.I. Orlova, V.A. Orlova, V.S. Kurazhkovskaya,
Crystallogr. Rep. 49 (2004) 614-618.
14

ACCEPTED MANUSCRIPT
[26] J. Isasi, A. Daidouh, Solid State Ionics 133 (2000) 303-313.
[27] I.V. Ogorodnyk, I.V. Zatovsky, N.S. Slobodyanik, V.N. Baumer, O.V. Shishkin, J.
Solid State Chem. 179 (2006) 3461-3466.
[28] S.T. Norberg, Acta Crystallogr. Sect. B: Struct. Sci. B58 (2002) 743-749.
[29] P.D. Battle, T.C. Gibb, S. Nixon, T.A. Harrison, J. Solid State Chem. 75 (1988) 21-
29.
[30] E.S. Zolotova, Z.A. Solodovnikova, B.M. Ayupov, S.F. Solodovnikov, Russian J.
Inorg. Chem. 56 (2011) 1216-1221.
[31] J.J. Carvajal, I. Parreu, R. Sole, X. Solans, F. Dıaz, M. Aguilo, Chem. Mater. 17
(2005) 6746-6754.
[32] J.C.M. Gustafsson, S.T. Norberg, G. Svensson, J. Albertsson, Acta Crystallogr.,
Sect. C: Cryst. Struct. Commun. C61 (2005) i9-i13.
[33] I.V. Ogorodnyk, V.N. Baumer, I.V. Zatovsky, N.S. Slobodyanik, O.V. Shishkin,
K.V. Domasevitch, Acta Crystallogr., Sect. B: Struct. Sci. B63 (2007) 819-827.
[34] M.A. Nabar, D.S. Phanasoaonkar, Spectrochim. Acta 37A (1981) 279-281.
[35] A.I. Orlova, A.K. Koryttseva, E.E. Loginova, Radiochemistry 53 (2011) 51-62.
[36] A.R. Zaripov, V.A. Orlova, V.I. Petkov, O.M. Slyunchev, D.D. Galuzin, S.I.
Rovnyi, Russ. J. Inorg. Chem. 54 (2009) 45-51.
[37] S.P. Kumar, G. Buvaneswari, J. Nuc. Mater. 458 (2015) 224-232.
[38] S.P. Kumar, G. Buvaneswari, Mater. Res. Bull. 48 (2013) 324-332.
[39] O. Terra, N. Clavier, N. Dacheux, R. Podor, New J. Chem. 27 (2003) 957-967.
[40] R.G. Brown, S.D. Ross, Spectrochim. Acta. 26A (1970) 1149-1153.
[41] R.D. Shannon, Acta Crystallogr. Sect. A. 32 (1976) 751-757.
15

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[42] K. Boughzala, E.B. Salem, A.B. Chrifa, E. Gaudin, K. Bouzouita, Mater. Res. Bull.
42 (2007) 1221-1229.
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Table 1. Lattice parameter of KBaYZrP2SiO12 and KBaYSnP2SiO12
Compounds
Lattice parameter (Å)
b
Volume (Å3)
a
c
KBaYZrP2SiO12
KBaYSnP2SiO12
10.30 (5)
10.28 (5)
10.82 (7)
10.22 (7)
10.20 (9)
10.54 (4)
1138
1108
Table 2. Comparison of unit cell parameters of KBaREE3+ZrP2SiO12
Compounds
Lattice parameter (Å)
Volume (Å3)
a
b
c
KBaYZrP2SiO12
KBaLaZrP2SiO12
10.30 (5)
10.25 (5)
10.76 (1)
10.86 (4)
10.68 (5)
10.28 (6)
10.26 (4)
10.39 (5)
10.82 (7)
10.46 (6)
10.40 (5)
10.06 (7)
10.20 (4)
10.22 (4)
10.71 (6)
10.28 (4)
10.20 (9)
10.93 (9)
10.27 (4)
10.14 (5)
10.38 (8)
10.54 (6)
10.16 (6)
10.71 (1)
1138
1173
1151
1109
1131
1109
1118
1145
KBaNdZrP2SiO12
KBaSmZrP2SiO12
KBaEuZrP2SiO12
KBaGdZrP2SiO12
KBaDyZrP2SiO12
KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12

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Table 3. Assignment of IR bands of KBaREE3+ZrP2SiO12
3-
4-
Compositions
PO4
SiO4
υ1
υ2
υ3
(cm-1)
υ4
(cm-1)
υ1
(cm-1)
υ2
υ3
(cm-1)
υ4
(cm-1)
770
743
742
736
743
740
731
(cm-1) (cm-1)
(cm-1)
445
458
448
435
431
428
436
KBaYZrP2SiO12
KBaLaZrP2SiO12
KBaNdZrP2SiO12
KBaSmZrP2SiO12
KBaEuZrP2SiO12
KBaGdZrP2SiO12
KBaDyZrP2SiO12
919
939
951
936
939
926
926
497
494
499
472
482
485
483
1054, 1014 553, 580
-
-
-
-
-
-
-
-
-
-
-
-
-
-
1024
1012
1037
1024
1038
1049
545, 594
558, 586
559, 584
553, 573
550
564
Table 4. Normalized mass loss of KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12
Days
Normalized Elemental Mass Loss (g/m2)
Ba×10-2
Zr×10-4
Si×10-1
1
3
5
7
0.13
0.24
0.35
0.45
0.62
0.80
0.99
1.13
1.35
1.37
1.56
1.73
1.89
2.08
2.04
1.98
0.78
0.85
1.24
1.16
1.32
1.24
0.93
0.99
1.09
1.09
0.93
0.93
0.78
0.78
0.78
0.62
0.33
1.65
2.52
3.44
0.26
0.07
-
-
-
-
-
-
-
-
-
-
9
11
13
15
17
19
21
23
25
27
29
31
* K, Y, La, Nd, Sm, Eu, P – Below the detection limit (BDL)
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Figure captions
Fig. 1. Powder XRD patterns of a. KBaYZrP2SiO12 and b. KBaYSnP2SiO12
Fig. 2. FTIR spectra of a. KBaYZrP2SiO12 and b. KBaYSnP2SiO12
Fig. 3. a, b) Lower and higher magnified SEM images of KBaYZrP2SiO12 and c, d)
Lower and higher magnified SEM images of KBaYSnP2SiO12
Fig. 4. Powder XRD patterns of KBaREE3+ZrP2SiO12 where REE3+ = a. Y, b. La, c. Nd,
d. Sm, e. Eu, f. Gd, g. Dy
Fig. 5. Powder XRD patterns of a) KBaYZrP2SiO12 and b)
KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12
Fig. 6. FTIR spectra of a) KBaYZrP2SiO12 and b) KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12
Fig. 7. TGA curve of KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12
Fig. 8. a, b) Lower and higher magnified SEM images and c) EDX spectrum of
KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12
Fig. 9. Leach rates of Ba and Zr for KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12
Fig. 10. Powder XRD patterns of KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12 a) before and b)
after leaching

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Fig. 1
b
a
10
20
30
40
50
60
70
2
θ
(o )
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Fig. 2
b
a
2000
1500
1000
500
Wavenumber (cm-1)
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Fig. 3
a
b
d
c
b
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Fig. 4
g
f
e
d
c
b
a
10
20
30
40
(o)
50
60
70
2
θ
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Fig. 5
b
a
1 0
2 0
3 0
4 0
5 0
6 0
7 0
2
θ
(o )
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Fig. 6
100
80
60
40
20
a
b
2000 1800 1600 1400 1200 1000
800
600
400
-1
Wavenumber (cm )
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Fig. 7
101
100
99
98
97
96
95
0
200
400
600
800
1000
Temperature (oC)
8

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Fig. 8
b
a
c
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Fig. 9
-5
8.0x10
Zr
-5
6.0x10
-5
4.0x10
-5
2.0x10
0.0
-3
1.4x10
-3
1.2x10
Ba
-3
1.0x10
-4
8.0x10
-4
6.0x10
0
5
10
15
20
25
30
Time(days)
10