Electrical and Vibrational Studies of Na2K2Cu(MoO4)3

Dridi, Wassim; Zid, Mohamed Faouzi; Maczka, Miroslaw

doi:https://doi.org/10.1155/2017/6123628

Advances in Materials Science and Engineering

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Abstract Introduction Experimental Results and Discussion Conclusion Conflicts of Interest References Copyright Related Articles

Research Article | Open Access

Volume 2017 | Article ID 6123628 | https://doi.org/10.1155/2017/6123628

Electrical and Vibrational Studies of Na₂K₂Cu(MoO₄)₃

Wassim Dridi,¹Mohamed Faouzi Zid,¹and Miroslaw Maczka²

Academic Editor: Pascal Roussel

Received01 Dec 2016

Revised06 Mar 2017

Accepted27 Mar 2017

Published11 Jun 2017

Abstract

The complex impedance of Na₂K₂Cu(MoO₄)₃ material has been investigated in the temperature range of 653–753 K and in the frequency range of 40 Hz–5 MHz. Electrical behavior of the studied material is explained through an equivalent circuit model which takes into account the contributions of grains and grains boundaries. The number of vibrational modes was calculated using group theoretical approach. The infrared and Raman spectra have also been measured and vibrational assignment has been proposed.

1. Introduction

A great deal of interest has been devoted to the chemistry of molybdenum; a significant number of new molybdates have been synthesized and characterized. Molybdate chemistry has developed rapidly and this development can be explained by several factors, especially the improvement of the structural X-ray diffraction analysis, which has been a fundamental tool used for determination of crystal structures. But this renewed interest is also explained by the fact that many molybdates are suitable materials for technological applications. Molybdates exhibit various physicochemical properties, which are related to both the nature of the elements associated with the molybdate groups and the degree of opening of the formed framework. In these materials, the anionic framework is usually built from MoO₄ tetrahedra linked to the transition metal polyhedra, leading to a large variety of crystal structures with a high capacity for cationic substitution. The chemistry of inorganic molybdate materials has been significantly advanced thanks to their valuable electrical and optical properties, which make them promising for various applications such as photoluminescence [1], ionic conductivity [2–4], laser materials [5, 6], and piezoelectrics [7]. The high-temperature superconductivity present in the copper-oxygen ceramic systems resulted in an increasing structural and physicochemistry interest of materials containing Cu-O [8]. Among these materials we can mention the copper molybdate Cu₃Mo₂O₉ doped with lithium, which displays high coulombic efficiency in lithium-ion batteries and excellent charge-discharge stability [9]. Another example is Li₂Cu₂(MoO₄)₃ material, which presents a high ionic conductivity (σ = 5.810⁻³ Ohm⁻¹·cm⁻¹ at 400 K, = 0.33 eV) [10].

The vibrational spectroscopic studies of molybdates have attracted particular attention of a large number of researchers [11–16]. This attention is due to the catalytic activity of () groups in hydrocarbons oxidations [17–20] and due to negative thermal expansion, ferroelasticity, and pressure-induced amorphization [21]. Furthermore, the interpretation of laser properties needs knowledge of vibrational level distribution [22]. According to this approach, we have decided to explore system A-Mo-Cu-O (A = alkali metal). The purpose of this study is to analyze the electrical response of the grain and grains boundaries effects, which greatly influence the electrical properties, and to understand the molecular structure at microscopic level of novel Na₂K₂Cu(MoO₄)₃ compound. This study can provide important information on the conductivity, which is very important for practical applications. In this paper, we will describe the synthesis method and the characterization of Na₂K₂Cu(MoO₄)₃ by Infrared, Raman, and complex impedance spectroscopies. Raman and IR selection rules will be also analyzed using factor group analysis.

2. Experimental

2.1. Polycrystalline Powder Synthesis of Na₂K₂Cu(MoO₄)₃

The Na₂K₂Cu(MoO₄)₃ polycrystalline powder was prepared by a conventional solid-state reaction from high-purity starting reagents of Na₂CO₃, K₂CO₃, Cu(CO₂CH₃)·H₂O, and (NH₄)₆Mo₇O₂₄·4H₂O. These reagents were weighted according to the stoichiometric ratio. They were mixed and ground together in an agate mortar and heated progressively to 773 K in porcelain crucible with intermittent cooling and regrindings. The powder was analyzed by X-ray powder diffraction, using a PAN-analytical X’Pert PRO X-ray diffractometer equipped with copper anticathode ( = 1.5406 Å). The unit cell parameters were refined using Celref 3.0 program and calculated to be as follows: = 7.5010() Å, = 9.3411() Å, and = 9.3670() Å and α = 92.59()°, β = 105.32()°, and γ = 105.44()°. The powder X-ray diffraction pattern was in agreement with single-crystal structure (Figure 1).

2.2. Complex Impedance Spectroscopy

Pellet was prepared by isostatic pressing at 4 kbar and sintering at 773 K for 12 h in air with 10 Kmin⁻¹ heating and cooling rates. The thickness and surface of pellet were about 0.22 cm and 1.25 cm² having a geometric factor of = 0.176 cm⁻¹. Electrical measurements were carried out in air by complex impedance spectroscopy using Agilent 4294A Precision Impedance Analyzer in the 40 Hz–5 MHz frequency range and 653–753 K temperature range. The sinusoidal AC voltage applied is of 0.5 V. The measuring cell having the sample inserted between two platinum discs used as ion-blocking electrodes is heated in an electric oven under dry air. The measurements were carried out after temperature stabilization of the device every 30 min with a pitch of 10 K. The advantage of this method lies in the fact that it is possible to separate the physical phenomena according to their speed; the fast phenomena will take place at high frequencies and the slow ones at low frequencies. Analysis of impedance spectroscopy data can provide information on charge carrier dynamics in ionic conductors [23].

2.3. Vibrational Spectroscopies

The infrared spectrum was recorded at room temperature using Thermo Scientific Nicolet iS50 FT-IR Spectrometer. The frequency range was from 400 to 4000 cm⁻¹ and the spectral resolution was 3 cm⁻¹. We are interested only in the domain 400–1100 cm⁻¹ containing the most significant solid-state absorption bands. To obtain the Raman spectrum of the powdered sample, LAB RAMAN HR800 spectrometer was used. The frequency range was from 100 to 1100 cm⁻¹ and the spectral resolution was 2 cm⁻¹. The measurement was carried out on a thin pellet. The sample was analyzed with an excitation wavelength of 632.81 nm and a power was adjusted to 1 mW in order to avoid any degradation. Spectroscopic studies are used to obtain the distribution of vibrational levels and assignment to the respective normal modes of Na₂K₂Cu(MoO₄)₃.

3. Results and Discussion

3.1. Structure Description

Na₂K₂Cu(MoO₄)₃ crystallizes in the triclinic space group P-1 with = 7.4946() Å, = 9.3428() Å, = 9.3619() Å, α = 92.591()°, β = 105.247()°, γ = 105.496()°, = 604.7(Å³), = 2, = 0.022, and = 0.056. Both cations K1 and K3 are located in the center of inversion, and all other atoms are at general positions. The structure of Na₂K₂Cu(MoO₄)₃ can be described as a one-dimensional framework formed by ribbons arranged in parallel to a axis with interribbons spaces containing Na⁺ and K⁺ monovalent cations directed to the free vertices of the tetrahedra MoO₄ (Figure 2). These structural characteristics encouraged us to study the electrical properties. CIF file containing complete information on the studied structure was deposited with FIZ Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany (fax: (+49)7247-808-666; e-mail: crysdata(at)fiz-karlsruhe(dot)de, deposition number CSD-430379).

3.2. Electrical Properties

The Nyquist plots in the temperature range from 653 K to 753 K are shown in Figure 3. When temperature increases, the radius of semicircles decreases and consequently the ionic conductivities increase with the temperature. We notice the presence of two hardly distinguishable semicircles, which proves the presence of two relaxation phenomena. The first arc existing towards higher frequencies corresponds to the movement of ions across the grain (bulk), which represents intrinsic conduction and gives rise to an intragranular resistance. The second arc, observed at lower-frequency, corresponds to movement of ions through the grain boundaries [24, 25]. The electrical behavior of Na₂K₂Cu(MoO₄)₃ is interpreted through an equivalent electrical circuit formed by two cells arranged in series, constituted by the parallel combination of the following: CPE1 corresponding to the contributions of grains and grains boundaries, respectively. and are the resistances of grains and grains boundaries, respectively. is the pure capacitance of grain and CPE1 is the fractal capacitance constant phase element according to grains boundary. Electrical parameters were measured as a function of temperature. The intercepts of the semicircular arcs with the real axis give an estimation of the resistance of the studied material. Zview software [26] was used to fit these curves. The total resistance, , follows the relation . The conformity between the experimental and calculated curves (fit) on the whole temperature range proves the validity of the proposed equivalent circuit. Electrical parameters are represented in Table 1.

In order to determine the direct conductivity for the grain interior , grain boundary , and total conductivity , we used the following equation:Values of ionic conductivities in Na₂K₂Cu(MoO₄)₃ material are represented in Table 2.

The activation energies was obtained by linear fitting of the ionic conductivities values at different temperatures by applying the Arrhenius equation: where σ is the temperature dependent ionic conductivity, is the ionic conductivity at absolute zero temperature, is the activation energy of cations migration, is the Boltzmann constant, and is the absolute temperature. The variation of (S·K·cm⁻¹)) versus (K⁻¹) is represented in Figure 4. Activation energies values are represented in Table 3.

We note that the total conductivity of our compound is less than the bulk conductivity but higher than the grain boundary one. This reveals the existence of a partial blockage of the charge carriers by the grain boundaries [27]. Therefore, the conductivity of our material is limited by the low conductivity of the grain boundaries. The influence of the grains boundaries conductivity on the total conductivity can be evaluated quantitatively by the blocking factor α. This parameter characterizes the fraction of the load carriers blocked in the case where a direct current flows through the sample. It can also be calculated using the following equation [28, 29]:Figure 5 shows the variation of the blocking factor as a function of the temperature. It is found that the blocking factor decreases with the temperature. Therefore, the increase in temperature causes a decrease in the blocking effect by the limits of the grains.

3.3. Vibrational Study

Na₂K₂Cu(MoO₄)₃ crystallizes in the triclinic space group P-1 which corresponds to factor group. There are two molecules per unit-cell, so there are also two molecules per Bravais cell. Mo1, Mo2, Mo3, Cu1, K2, Na1, Na1, and O atoms occupy symmetry whereas K1 and K3 atoms occupy symmetry. The Bravais cell comprises 40 atoms that have 120 zone center degrees of freedom. The structure of Na₂K₂Cu(MoO₄)₃ compound is centrosymmetric; a complete assignment of the crystal modes requires both IR and Raman spectra [30]. The crystal vibrational modes are obtained by group theoretical calculations developed by Fateley et al. [31]. Factor group analysis of Na₂K₂Cu(MoO₄)₃ is represented in Table 4. The vibrational irreducible representation for the triclinic phase at the center of the Brillouin zone () is3 acoustic and optic modes, where is the number of atoms in the unit cell [32]:Infrared and Raman active modes are as follows:In the free state tetrahedral MoO₄ ion has symmetry and four vibrational modes with the following wavenumbers: nondegenerate symmetric stretching at 936 cm⁻¹, doubly degenerate symmetric bending at 220 cm⁻¹, triply degenerate asymmetric stretching at 895 cm⁻¹, and triply degenerate asymmetric bending at 365 cm⁻¹ [33]. Moreover, all four vibrational modes are active in the Raman spectra, but only stretching and bending vibrations are active in the IR spectra. However, when this ion is located in the crystal lattice, its symmetry is lowered due to the constraints imposed by the lattice. So, the local symmetry of the three MoO₄ tetrahedra decreases to . Because of this lowering of symmetry, all modes become active in Raman and in infrared and degenerate modes raise their degenerations. Therefore, and are split into three bands and into two . The correlation between the point group of symmetry of the free anion MoO₄, its site-symmetry , and its factor group is represented in Scheme 1. According to Basiev et al. [34], the vibrational modes observed in Raman spectra of molybdates can be classified into two groups, internal and external modes. The internal vibrational modes of each type of MoO₄ derived from the correlation scheme are equal to , where is the number of atoms in the molecular MoO₄:The external vibrational modes of MoO₄ are divided into translational modes which includes acoustic and lattice modes and librational modes [35], presented as follows:The comparison of the infrared and Raman bands positions shows that the majority of these bands do not coincide. Indeed, the observed IR bands appear at wavenumbers different from those in the Raman spectrum (Figure 6). This is in agreement with the centrosymmetric character of Na₂K₂Cu(MoO₄)₃ structure [36]. The Raman spectrum can be separated into two parts with a wide empty gap in the range 500–700 cm⁻¹ that is commonly observed in molybdates containing MoO₄ tetrahedra [22, 37–43]. The proposed assignment of the vibrational spectra of MoO₄ in Na₂K₂Cu(MoO₄)₃ is realised by considering the following criteria: bands are generally very strong in the Raman and weaker in the infrared spectra, whereas an opposite behavior is usually observed for bands. bands are usually stronger in the Raman spectra than those corresponding to modes but in the infrared spectra band is generally more intense [44]. The Mo-O stretching modes are located in the range 720–930 cm⁻¹ whereas the bending modes are situated in the range 380–330 cm⁻¹. Wavenumbers and assignment of the internal vibrational modes of MoO₄ tetrahedron are listed in Table 5.

In the Raman spectrum, bands located below 300 cm⁻¹ are attributed to external vibrations involving the librational and translational modes of the MoO₄ anions and translational modes of cations; the distinguishing between librational and translational modes is difficult. But in general librational modes have higher wavenumbers and intensities than the translational modes [45]. Furthermore, since the atomic mass of molybdenum is larger than that of copper, potassium, and sodium, translations of the ions should be observed at lower wavenumbers than translations of Cu²⁺, K⁺, and Na⁺ [13]. Based on these rules, we propose assignment of the 273 cm⁻¹ band to (Na⁺) modes, those at 119 and 124 cm⁻¹ to (MoO₄) modes, and the remaining bands in the 138–199 cm⁻¹ range to the coupled modes involving translational motions of the molybdate, potassium, and copper ions.

4. Conclusion

Polycrystalline powder of Na₂K₂Cu(MoO₄)₃ was obtained by standard solid-state reaction at 773 K. X-ray diffraction studies show that this compound crystallizes in the triclinic symmetry with the P-1 space group. Ionic conductivity of the investigated material is characterized by the existence of a partial blockage of the charge carriers by the grain boundaries. The blocking effect generated by the limits of the grains decreases with temperature. The centrosymmetric space group P-1 of our structure is confirmed by the noncoincidence of majority of Raman and IR bands. Vibrational study indicates the lowering of symmetry of molybdate anion from to symmetry.

Conflicts of Interest

The authors declare that there are no conflicts of interest regarding the publication of this paper.

References

R. Grasser, E. Pitt, A. Scharmann, and G. Zimmerer, “Optical properties of CaWO₄ and CaMoO₄ crystals in the 4 to 25 eV region,” physica Status Solidi (b), vol. 69, no. 2, pp. 359–368, 1975.
View at: Publisher Site | Google Scholar
A. A. Savina, S. F. Solodovnikov, D. A. Belov et al., “Synthesis, crystal structure and properties of alluaudite-like triple molybdate Na₂₅Cs₈Fe₅(MoO₄)₂₄,” Journal of Solid State Chemistry, vol. 220, pp. 217–220, 2014.
View at: Publisher Site | Google Scholar
M. Hartmanova, M. T. Le, M. Jergel, V. Šmatko, and F. Kundracik, “Structure and electrical conductivity of multicomponent metal oxides having scheelite structure,” Russian Journal of Electrochemistry, vol. 45, no. 6, pp. 621–629, 2009.
View at: Publisher Site | Google Scholar
N. I. Sorokin, “Ionic conductivity of double sodium-scandium and cesium-zirconium molybdates,” Physics of the Solid State, vol. 51, no. 6, pp. 1128–1130, 2009.
View at: Publisher Site | Google Scholar
Y. Zhang, H. Cong, H. Jiang, J. Li, and J. Wang, “Flux growth, structure, and physical characterization of new disordered laser crystal LiNd(MoO₄)₂,” Journal of Crystal Growth, vol. 423, pp. 1–8, 2015.
View at: Publisher Site | Google Scholar
N. M. Kozhevnikova and O. A. Kopylova, “Synthesis and X-ray diffraction and IR spectroscopy studies of ternary molybdates Li₃Ba₂R₃(MoO₄)₈ (R = La-Lu, Y),” Russian Journal of Inorganic Chemistry, vol. 56, no. 6, pp. 935–938, 2011.
View at: Publisher Site | Google Scholar
A. E. Sarapulova, B. Bazarov, T. Namsaraeva et al., “Possible piezoelectric materials CsMZr_0.5(MoO₄)₃ (M = Al, Sc, V, Cr, Fe, Ga, In) and CsCrTi_0.5(MoO₄)₃: structure and physical properties,” Journal of Physical Chemistry C, vol. 118, no. 4, pp. 1763–1773, 2014.
View at: Publisher Site | Google Scholar
J. Hanuza, M. Andruszkiewicz, Z. Bukowski, R. Horyń, and J. Klamut, “Vibrational spectra and internal phonon calculations for the M₂Cu₂O₅ binary oxides (M = In, Sc, Y or from Tb to Lu),” Spectrochimica Acta Part A: Molecular Spectroscopy, vol. 46, no. 5, pp. 691–704, 1990.
View at: Publisher Site | Google Scholar
J. Xia, L. X. Song, W. Liu et al., “Highly monodisperse Cu₃Mo₂O₉ micropompons with excellent performance in photocatalysis, photocurrent response and lithium storage,” RSC Advances, vol. 5, no. 16, pp. 12015–12024, 2015.
View at: Publisher Site | Google Scholar
S. F. Solodovnikov, R. F. Klevtsova, and P. V. Klevtsov, “A correlation between the structure and some physical properties of binary molybdates (Tungstates) of uni- and bivalent metals,” Journal of Structural Chemistry, vol. 35, no. 6, pp. 879–889, 1994.
View at: Publisher Site | Google Scholar
S. S. Saleem, G. Aruldhas, and H. D. Bist, “Raman and infrared spectra of GdTb (MoO₄)₃ single crystal in the region 250–1000 cm-1,” Spectrochimica Acta Part A: Molecular Spectroscopy, vol. 39, no. 12, pp. 1049–1053, 1983.
View at: Publisher Site | Google Scholar
B. G. Bazarov, R. F. Klevtsova, T. T. Bazarova et al., “Double molybdate Tl₂Mg₄(MoO₄)₃: synthesis, structure, and properties,” Russian Journal of Inorganic Chemistry, vol. 51, no. 10, pp. 1577–1580, 2006.
View at: Publisher Site | Google Scholar
M. MacZka, A. Pietraszko, W. Paraguassu et al., “Structural and vibrational properties of K₃Fe(MoO₄)₂(Mo₂O₇)—a novel layered molybdate,” Journal of Physics Condensed Matter, vol. 21, no. 9, Article ID 095402, 2009.
View at: Publisher Site | Google Scholar
M. Isaac, V. U. Nayar, D. D. Makitova, V. V. Tkachev, and L. O. Atovmjan, “Infrared and polarized Raman spectra of LiNa₃(MoO₄)₂ · 6H₂O,” Spectrochimica Acta. Part A: Molecular and Biomolecular Spectroscopy, vol. 53, no. 5, pp. 685–691, 1997.
View at: Publisher Site | Google Scholar
N. M. Kozhevnikova, “Synthesis and phase formation study in K₂MoO₄-SrMoO₄-R₂(MoO₄)₃ systems (where R = Pr, Nd, Sm, Eu, and Gd),” Russian Journal of Inorganic Chemistry, vol. 57, no. 5, pp. 646–649, 2012.
View at: Publisher Site | Google Scholar
R. L. Frost, J. Bouzaid, and I. S. Butler, “Raman spectroscopic study of the molybdate mineral Szenicsite and comparison with other paragenetically related molybdate minerals,” Spectroscopy Letters, vol. 40, no. 4, pp. 603–614, 2007.
View at: Publisher Site | Google Scholar
S. S. Saleem, “Infrared and Raman spectroscopic studies of the polymorphic forms of nickel, cobalt and ferric molybdates,” Infrared Physics, vol. 27, no. 5, pp. 309–315, 1987.
View at: Publisher Site | Google Scholar
Y. S. Yoon, W. Ueda, and Y. Moro-oka, “Selective conversion of propane to propene by the catalytic oxidative dehydrogenation over cobalt and magnesium molybdates,” Topics in Catalysis, vol. 3, no. 3-4, pp. 265–275, 1996.
View at: Publisher Site | Google Scholar
W. Ueda, Y.-S. Yoon, K.-H. Lee, and Y. Moro-oka, “Catalytic oxidation of propane over molybdenum-based mixed oxides,” Korean Journal of Chemical Engineering, vol. 14, no. 6, pp. 474–478, 1997.
View at: Publisher Site | Google Scholar
J. D. Pless, B. B. Bardin, H.-S. Kim et al., “Catalytic oxidative dehydrogenation of propane over Mg-V/Mo oxides,” Journal of Catalysis, vol. 223, no. 2, pp. 419–431, 2004.
View at: Publisher Site | Google Scholar
M. MacZka, A. G. Souza Filho, W. Paraguassu, P. T. C. Freire, J. Mendes Filho, and J. Hanuza, “Pressure-induced structural phase transitions and amorphization in selected molybdates and tungstates,” Progress in Materials Science, vol. 57, no. 7, pp. 1335–1381, 2012.
View at: Publisher Site | Google Scholar
J. Hanuza and L. Macalik, “Polarized i.r. and Raman spectra of orthorhombic KLn(MoO₄)₂ crystals (Ln = Y, Dy, Ho, Er, Tm, Yb, Lu),” Spectrochimica Acta Part A: Molecular Spectroscopy, vol. 38, no. 1, pp. 61–72, 1982.
View at: Publisher Site | Google Scholar
A. Lasia, Electrochemical Impedance Spectroscopy and Its Applications, vol. 32 of Modern Aspects of Electrochemistry, Springer US, 2002.
B. Louati and K. Guidara, “Dielectric relaxation and ionic conductivity studies of LiCaPO₄,” Ionics, vol. 17, no. 7, pp. 633–640, 2011.
View at: Publisher Site | Google Scholar
H. Mahamoud, B. Louati, F. Hlel, and K. Guidara, “Impedance and modulus analysis of the (Na_0.6Ag_0.4)₂PbP₂O₇ compound,” Journal of Alloys and Compounds, vol. 509, no. 20, pp. 6083–6089, 2011.
View at: Publisher Site | Google Scholar
D. Johnson, Zview Version 3.1c, Scribner Associates, 1990–2007.
R. Ben Said, B. Louati, and K. Guidara, “Conductivity behavior of the new pyrophosphate NaNi_1.5P₂O₇,” Ionics, vol. 22, no. 2, pp. 241–249, 2016.
View at: Publisher Site | Google Scholar
R. Gerhardt and A. S. Nowick, “Grain‐boundary effect in ceria doped with trivalent cations: I, electrical measurements,” Journal of the American Ceramic Society, vol. 69, no. 9, pp. 641–646, 1986.
View at: Publisher Site | Google Scholar
M. J. Verkerk, B. J. Middelhuis, and A. J. Burggraaf, “Effect of grain boundaries on the conductivity of high-purity ZrO₂—Y₂O₃ ceramics,” Solid State Ionics, vol. 6, no. 2, pp. 159–170, 1982.
View at: Publisher Site | Google Scholar
J. Hanuza, “Raman scattering and infra-red spectra of tungstates KLn(WO₄)₂ family (Ln = La÷Lu),” Journal of Molecular Structure, vol. 114, pp. 471–474, 1984.
View at: Publisher Site | Google Scholar
W. G. Fateley, F. R. Dollish, N. J. McDevitt, and F. F. Bentley, Infrared and Raman Selection Rules for Molecular and Lattice Vibrations: The Correlation Method, John Wiley & Sons, New York, NY, USA, 1972.
E. D. Palik, Handbook of Optical Constants of Solids, vol. 2, Academic Press, 1991.
K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Mir, Moscow, Russia, 1966.
T. T. Basiev, A. A. Sobol, P. G. Zverev, L. I. Ivleva, V. V. Osiko, and R. C. Powell, “Raman spectroscopy of crystals for stimulated Raman scattering,” Optical Materials, vol. 11, no. 4, pp. 307–314, 1999.
View at: Publisher Site | Google Scholar
L. Nalbandian and G. N. Papatheodorou, “Raman spectra and molecular vibrations of Au₂Cl₆ and AuAlCl₆,” Vibrational Spectroscopy, vol. 4, no. 1, pp. 25–34, 1992.
View at: Publisher Site | Google Scholar
S. Kaoua, S. Krimi, S. Péchev et al., “Synthesis, crystal structure, and vibrational spectroscopic and UV-visible studies of Cs₂MnP₂O₇,” Journal of Solid State Chemistry, vol. 198, pp. 379–385, 2013.
View at: Publisher Site | Google Scholar
J. Hanuza, L. Macalik, and K. Hermanowicz, “Vibrational properties of KLn(MoO₄)₂ crystals for light rare earth ions from lanthanum to terbium,” Journal of Molecular Structure, vol. 319, pp. 17–30, 1994.
View at: Publisher Site | Google Scholar
V. V. Atuchin, O. D. Chimitova, T. A. Gavrilova et al., “Synthesis, structural and vibrational properties of microcrystalline RbNd(MoO₄)₂,” Journal of Crystal Growth, vol. 318, no. 1, pp. 683–686, 2011.
View at: Publisher Site | Google Scholar
V. V. Atuchin, V. G. Grossman, S. V. Adichtchev, N. V. Surovtsev, T. A. Gavrilova, and B. G. Bazarov, “Structural and vibrational properties of microcrystalline TlM(MoO₄)₂ (M = Nd, Pr) molybdates,” Optical Materials, vol. 34, no. 5, pp. 812–816, 2012.
View at: Publisher Site | Google Scholar
V. V. Atuchin, O. D. Chimitova, S. V. Adichtchev et al., “Synthesis, structural and vibrational properties of microcrystalline β-RbSm(MoO₄)₂,” Materials Letters, vol. 106, pp. 26–29, 2013.
View at: Publisher Site | Google Scholar
L. Macalik, “Comparison of the spectroscopic and crystallographic data of Tm³⁺ in the different hosts: KLn(MO₄)₂ where Ln=Y,La,Lu and M=Mo,W,” Journal of Alloys and Compounds, vol. 341, no. 1-2, pp. 226–232, 2002.
View at: Publisher Site | Google Scholar
L. Macalik, E. Tomaszewicz, M. Ptak, J. Hanuza, M. Berkowski, and P. Ropuszynska-Robak, “Polarized Raman and IR spectra of oriented Cd_0.9577Gd_0.0282□_0.0141MoO₄ and Cd_0.9346Dy_0.0436□_0.0218MoO₄ single crystals where □ denotes the cationic vacancies,” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 148, pp. 255–259, 2015.
View at: Publisher Site | Google Scholar
V. Dmitriev, V. Sinitsyn, R. Dilanian et al., “In situ pressure-induced solid-state amorphization in Sm₂(MoO₄)₃, Eu₂(MoO₄)₃ and Gd₂(MoO₄)₃ crystals: chemical decomposition scenario,” Journal of Physics and Chemistry of Solids, vol. 64, no. 2, pp. 307–312, 2003.
View at: Publisher Site | Google Scholar
E. J. Baran, M. B. Vassallo, C. Cascales, and P. Porcher, “Vibrational spectra of double molybdates and tungstates of the type Na₅Ln(XO₄)₄,” Journal of Physics and Chemistry of Solids, vol. 54, no. 9, pp. 1005–1008, 1993.
View at: Publisher Site | Google Scholar
S. S. Saleem and G. Aruldhas, “Raman and infrared spectra of lanthanum molybdate,” Journal of Solid State Chemistry, vol. 42, no. 2, pp. 158–162, 1982.
View at: Publisher Site | Google Scholar

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