Crystal structure, spectroscopic, magnetic and dielectric studies of new doped ceramic ZrTe3O8:7%CuO

Journal Pre-proof Crystal structure, spectroscopic, magnetic and dielectric studies of new doped ceramic ZrTe3O8:7%CuO M. Koubaa, R. Karray, L. Bessais, A. Kabadou PII:

S0925-8388(20)30337-6

DOI:

https://doi.org/10.1016/j.jallcom.2020.153974

Reference:

JALCOM 153974

To appear in:

Journal of Alloys and Compounds

Received Date: 14 May 2019 Revised Date:

19 January 2020

Accepted Date: 20 January 2020

Please cite this article as: M. Koubaa, R. Karray, L. Bessais, A. Kabadou, Crystal structure, spectroscopic, magnetic and dielectric studies of new doped ceramic ZrTe3O8:7%CuO, Journal of Alloys and Compounds (2020), doi: https://doi.org/10.1016/j.jallcom.2020.153974. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier B.V.

Credit author statement M. Koubaa: Software, Formal analysis, Investigation, Visualization, Data curation. R. Karray: Conceptualization, Methodology, Writing - Review & Editing, Validation. A. Kabadou: Validation, Writing- Original draft preparation, Supervision, Writing- Reviewing and Editing.

Figures captions : Fig. 1. X-ray powder diffraction pattern and refinement of ZrTe3O8:7%CuO. Fig. 2. Perspective view of the ZrTe3O8:7%CuO unit cell showing the Zirconium/copper polyhedron. Fig. 3. Te-O-Te cycle projection: (a) along a axis; (b) along b axis; (c) along c axis and (d) along [111]. Fig. 4. Te-O-Te cycle projection +ZrO6 octahedra: (a) along a axis; (b) along b axis; (c) along c axis and (d) along [111]. Fig. 5. Raman spectra of ceramic ZrTe3O8 and ZrTe3O8:7%CuO at room temperature. Fig. 6. FTIR spectra after heat treatment of base ceramic and ZrTe3O8:7%CuO at 750 °C in the range 4000 cm-1 to 400 cm-1 at room temperature. Fig . 7. TGA curve of ZrTe3O8:7%CuO compound. Fig. 8. Evolution of absorption spectra of ZrTe3O8:7%CuO. Fig. 9. Temperature dependence of magnetization for ZrTe3O8:7%CuO sample at a magnetic field of 0.05 T. Fig. 10. Evolution of magnetic susceptibility and its reverse for ZrTe3O8:7%CuO compound. Fig. 11. The magnetization hysteresis curve (M versus H) measured at 10 K and in external magnetic fields from -5 to +5 Tesla for ZrTe3O8:7%CuO compound. Fig. 12. Variation of ε′ with temperature for ZrTe3O8:7%CuO ceramic: (a) at low frequencies and (b) at high frequencies. Fig. 13. Variation of ε″ with temperature for ZrTe3O8:7%CuO ceramic: (a) at low frequencies and (b) at high frequencies. Fig. 14. Temperature-dependent loss tangent of ZrTe3O8:7%CuO ceramic: (a) at low frequencies and (b) at high frequencies. Fig. 15. Frequency dependence of the real part M′ at different temperatures. Fig. 16. Frequency dependence of the imaginary part M″ at different temperatures. Fig. 17. Complex impedance curves of ZrTe3O8:7%CuO compound at various temperatures. Fig. 18. Equivalent circuit of ZrTe3O8:7%CuO compound at 713 K.

Crystal structure, spectroscopic, magnetic and dielectric studies of new doped ceramic ZrTe3O8:7%CuO M. Koubaaa*, R. Karraya, L. Bessaisb, A. Kabadoua a

b

Laboratoire des Sciences des Matériaux et d’Environnement, Faculté des Sciences de Sfax-3018, Tunisia CMTR, ICMPE,UMR7182,CNRS – University Paris Est Créteil,2-8rue Henri Dunant,F-94320 Thiais, France

*Corresponding Author. E-mail [email protected]; Tel: (+216 20 681 709)

Abstract In this study, calcined ZrTe3O8 powder mixed with 7%wt of CuO was sintered at 750 °C. The new doped ceramic ZrTe3O8:7%CuO was synthesized using solid state reaction method and was studied with X-ray diffraction (XRD). At room temperature, the title compound crystallizes in cubic space group Ia3, with lattice parameter a = 11.328(3) Å, and exhibits a complex network of interconnected closed chains built up of TeO4E (E = electronic lone pair of Te (IV) atoms). The Zr/CuO6 octahedra are inserted into these chains ensuring the stability of the structure by Zr/Cu -O-Te bonding contacts. IR and Raman spectroscopic study are employed as means to obtain preliminary structural information and confirms the presence of the ZrO6 and TeO4E groups. Optical properties of the ceramic were explored by using UV– Vis absorption. The magnetic results reveal the appearance of a weak ferromagnetic behavior at low temperature (TC = 46.172 K). In addition, dielectric data were analyzed using real and imaginary permittivity ε′ and ε′′ respectively, the tan (δ) and the electrical modulus (M  and M″) for the sample ZrTe3O8:7%CuO at various frequencies. The Z ′ and Z ′′ versus frequency plots are well fitted to an equivalent circuit model composed of a series combination of two parallel combinations of resistance Ri and constant phase element CPEi. Keywords: Raman spectroscopy; Optical properties; Magnetic; Conductivity; Modulus; Equivalent circuit.

1. Introduction Last year the strong interest in tellurium oxides serving in various technologic field and in particular in MTe3O8 compounds has led to a wealth of experimental data. Indeed, a large number of crystal structure and physical properties were reported: M = (Sn, Hf, Ti and Zr)[1]. This family ceramics adopt generally the Ia3 cubic arrangement and were considered as portentous dielectric materials for low temperature co-fired ceramics (LTCC) applications [2-6]. Scientist continues advising novel materials to attempt newer

sophisticated properties. Our research team is recently interested with ZrTe3O8 compound. The latter possesses a cubic structure with space group Ia3 and lattice parameter a = 11.308(1) Å [7]. The lattice consists of corner sharing conventional trigonal bipyramids Tbps TeO4 and isolated slightly distorted ZrO6 octaedra. Properties of ZrTe3O8 can be tuned by doping with various metal atoms to suit specific needs. The metal doping generally induce drastic changes in structural, electrical and magnetic properties. For this, in our previous investigations, we examinated the effect of manganese doping on ZrTe3O8 vibrational and physical properties [8]. The incorporation of divalent cation such as Cu2+ ions should have an even stronger influence on these properties, though due to the different valency, it is probably more difficult to incorporate divalent cations into the lattice. Thus this investigation deals with the syntheses of undopped and 7%CuO doped ZrTe3O8 ceramic powder via solid state method. Different characterizing techniques such as X-ray powder diffraction (XRPD), Infrared absorption, TGA, Magnetic and Electrical impedances have been employed. The effect of Cu2+ ion incorporation on structural, spectroscopic, electrical and magnetic properties has also been reported.

2. Experimental techniques 2.1. Synthesis ZrTe3O8:7%CuO, solid solution, was synthesized by the conventional solid state reaction method. For ZrTe3O8 composition, TeO2 and ZrO2 very pure powders (99.99%) were carefully weighed in a molar ratio of 3:1 respectively and thoroughly mixed in agate mortar. The mixture was next heated during 15 hours at 700 °C. Following the thermal cycle we repeat grinding the obtained powder for 30 min. For prepared ZrTe3O8 ceramic we now realize doping with CuO (99.99%) at mole percent 7%. The result mixture is crushed after stirring in ethanol for 24 hours. The powder was added with 15%-PVA solution and pressed into disc-shaped compacts using uniaxial pressure of 1 tons/cm2. The samples were then heat treated at 550 °C for 2 h to eliminate the PVA, followed by sintering at 750 °C for 10 h (heating rate = 10 °C/min). The obtained powder was mounted in the top-loaded sample holder and investigated by X-ray powder diffraction (XRPD). 2.2. Characterization X-ray powder data were collected at room temperature using a D8 Bruker diffractometer equipped with a dichromatic copper radiation Kα1 and Kα2 (λ1 = 1.5406 Å and λ2 = 1.5444 Å)

with constant (2θ) steps of 0.0119. The X-ray powder diffraction data were refined by the Rietveld method [9,10] using the FULLPROF program [11]. The refinement with the halfwidth parameters U, V, W, unit cell parameters mixing coefficient η and the symmetry parameters converged to χ2 = 2.09%. Then the assumed structure was refined while fixing the profile and instrumental parameters and led to Rp = 5.88%, Rwp = 8.02% and Gof = 1.4. Raman spectrum of powder, was obtained at 298 K with a HoriboJobin Yvan HR800 microcomputer system instrument using a conventional scanning Raman instrument equipped with a Spex 1403 double monochromator and a Hamamatsu 928 photomultiplier detector. The excitation radiation was provided by coherent radiation with a He–Neon laser at a wavelength of 633 nm, and the output laser power was 50 mW. The spectral resolution, in terms of slit width, varied from 3 to 1 cm-1. Infrared absorption spectrum was obtained from a solid sample palletized in KBr and recorded on a Perkin-Elmer 1750 spectrophotometer IR-470 in the range 400–4000 cm-1. TGA measurements were carried out on 5–10 mg using a Perkin–Elmer TGA7 instrument, the analysis was conducted in the temperature range 500–850 °C in a nitrogen atmosphere under a constant flow rate of 10 ml.min–1. The absorption spectra were measured at wavelengths ranging between 200 and 850 nm, using a UV–visible spectrophotometer (SAFAS UVmc). Magnetic measurements were performed using a physical property measurement system (PPMS) magnetometer from Quantum Design operating up to 5 T. The magnetic ordering temperature was determined from temperature dependence of the magnetization measured in magnetic field of 0.05 T and in a temperature range of 10-300 K. Electrical impedances were measured in the frequency range from 209 Hz to 4.85 MHz with a TEGAM 3550 ALF automatic bridge monitored by a micro-computer between 588 and 713 K.

3. Results and discussion 3.1. Structure description Refinement of profile and structural parameters yield to good structure factors RF = 5.31%, Rbragg = 5.93%, χ2 = 2.09% and profile factors (Rp = 5.88%; Rwp = 8.02%; Rexp = 5.54% and gof = 1.4). No second phase was detected probably as ZrTe3O8 is the only ternary compound known to exist in the ZrO2-TeO 2 pseudobinary system [12].

Hence the doped ZrTe3O8 crystallize well into the assumed cubic distorted fluorine-type structure with the space group Ia3 at room temperature as described by authors for pure ZrTe3O8 [1,7] while others found that it has the I213 space group [13]. ZrTe3O8 crystal is isomorphous with TiTe3O8 crystal [1]. MTe3O8 (M = Ti, Zr, Sn and Hf) crystals are composed of MO6 octahedra and TeO4 tbps (trigonal bipyramid). The MO6 octahedron shares a common oxygen atom with TeO4 tbp forming Te-eqO-M linkage and three TeO4 tbps are connected by sharing axial vertices yielding three-coordinated oxygen atom. Graphical representation of the ZrTe3O8:7%CuO structure was performed using DIAMOND [14]. The Te atoms occupy the 24d sites of the Ia3 space group, surrounded by oxygen atoms lying in the 48e and 16c positions. The Zr/Cu atoms occupy the 8a (0.25, 0.25, 0.25) sites. Fig. 1 illustrates the final Rietveld plot for ZrTe3O8:7%CuO. Perspective view is shown in Fig. 2. Crystal structure data and experimental conditions were collected in Table 1. Positions and isotropic thermal parameters were presented in Table 2. The lattice parameters and the bond distances for both ZrTe3O8:7%CuO and ZrTe3O8 [1] samples were reported in Table 3. Every Te atom has two axial neighboring oxygen atoms of O(1) type at a distance for about 2.172(2) Å and two equatorial oxygen atoms of O(2) type at 1.850(2) Å. Thus, with these four nearest oxygen atoms, each Te atom builds the classically TeO4E polyhedron in view of a trigonal bipyramid, called disphenoid. Its ‘axis’ is formed by the two long Te–O bonds, whereas the equatorial plane includes the two short Te–O bonds and the 5s2 lone electron pair E pointing in the direction of the third equatorial corner. Closed chains Te-Oax-Te like cycles is formed via corner sharing TeO4 units. Each cycle has a very particular and unusual shape and contains exactly 10 Te atoms as shown in Fig. 3. Cycles are interconnected with O(1) atom, as every O(1) atom must have three Te-O bands, resulting in a very complex Te-O-Te network. The Zr/Cu atoms are sixfold coordinated with O(2)-type oxygen atoms forming a slightly distorted octahedron (O(2)-Zr/Cu-O(2) = 88.93°(3)/180.00°(1)) with Zr/Cu-O distance of 2.092(2) Å. Each Zr/CuO6 octahedron shares a common oxygen atom with a TeO4 (tbps) forming …-Zr-Oeq(2)-Te-… bridges thus ensuring crystal structure cohesion (Fig. 4). The Zr/Cu–Oeq(2) bond distance for ZrTe3O8:7%CuO was slightly bigger than that observed for pure ZrTe3O8 (2.037(2) Å), in addition the Te–Oax(1) bond length for ZrTe3O8:7%CuO also increased faintly, which may be the reason of the lattice parameter increasing from

11.308(1) to 11.328(3) Å (Table 3). This fact is probably due to the slight differences in chemical composition between the two samples. A Raman study was carried out to confirm these results. 3.2.Vibrational study 3.2.1. Raman Spectroscopic Study The Raman study was limited to the frequency range 50 to 1000 cm-1. The middle and highest frequency parts of the Raman spectra are related with stretching vibrations of the X– O–X bridges so that Raman-active bands in the high-frequency region is associated to nonbridging (terminal) X–O bonds [15] and Raman-active bands in the middle-frequency region is associated to the X–O–X bridges. The Raman spectrum scattering of the synthesized phase ZrTe3O8:7%CuO is characterized by two overlapping peaks, the first peak which is the most intense appears around 112 cm-1 and the second peak which is less intense appears at about 149 cm-1, corresponding to isolated TeO2 entities translation and rotation, respectively. Three major bands at 700, 755 and 782 cm-1 assigned to Te–O stretching vibration of TeO4 tbp units [16] while the new band appeared at 732 cm-1 may be attributed to the Te-O-Cu bridges vibration [12]. The Raman spectrum also shows an intense band observed at 460 cm-1 assigned to symmetric stretching vibration of Te-O-Zr/Cu bridges. While that observed at 859 cm-1 is attributed to the asymmetric stretching. The assignment of these two bands is the same whatever the considered cation (Ti, Zr and Sn) [17,18], whereas theirs intensities vary with the cation nature. Therefore the Raman scatterings of ZrTe3O8 and ZrTe3O8:7%CuO are given in the Fig. 5 for comparison. The intensity band at 859 cm-1 decreased, slightly while that around 460 cm-1 increased. This indicates that the Te-O(2)-Zr bridges in ZrTe3O8:7%CuO are more symmetric than the TeO(2)-Zr bridges observed in pure ZrTe3O8. According to the spectroscopic study, it was confirmed that there is no change in structure. 3.2.2. Infrared spectrum The IR study was restricted to the frequency range 400 to 4000 cm−1. The IR spectrum is presented in Fig. 6. The vibrational bands and their frequencies are given in Table 4. This 

analysis shows the presence of the bands corresponding to equatorial symmetric (ν ) ,  equatorial asymmetric(ν ) and axial symmetric (ν ) vibrations at 787 (F), 704 (m), 666 (m)

relative to (Te-O) bands and the band at 415 (m) cm-1 can be assigned to Zr-O stretching

vibrations. The spectrum exhibit a spectral band at about 486 cm-1 related to the stretching vibrations of Te–O–Te linkages between TeO4 trigonal bipyramids (tbp). The band appeared at 513 cm-1 may be attributed to stretching mode vibration of Cu-O [19,20]. 3.3. TG analysis According to TGA results, there was no weight loss associated with the melting reaction. The thermal curve shows that ZrTe3O8:7%CuO phase is stable up to the temperature 800 °C, beyond which it starts to deteriorate (Fig. 7). 3.4.Optical properties The UV-Vis spectroscopy is a perfect mean to study colored transition metal complexes. d-d transitions bands generally fall in this region. The spectrum of ZrTe3O8:7%CuO was recorded in 200-850 nm region and presented in Fig. 8. In the UV region, broad absorption bands around 200-350 nm are seen and assigned to O2-→ Zr4+ , O2-→ Cu2+ ligand to metals charge transfer transitions [21-23], the Te4+ cations additionally contribute to the charge-transfer band with s → p transitions of their lone pairs. A broad peak with maximum absorption value 0.5 was observed around the 770 nm wavelength, which is the typical region of Cu2+ absorption in the Oh symmetry [24,25] and is related to the electronic transfers caused by the legend field splitting of d levels. The d9 configuration should make Cu2+ subject to Jahn-Teller distortion when placed in cubic symmetry environment. The same behavior was reported especially in the experimentally better studied system MgO:Cu2+ that has been explored using EXAFS by several groups [2627] and confirms the cubic geometry of the complex. 3.5. Magnetic measurements Magnetic measurements of ZrTe3O8:7%CuO compound was effectuated in the [10-300] K temperature range, using a magnetometer Physical Properties Measurement System (PPMS). In Fig. 9 the temperature dependence of the magnetization (M-T) curve measured in the 10-300 K) temperature range in the field 0.05 T shows an increase of the magnetization below a transition temperature TC, which is the inflection point of the curve determined using the numerical derivative dM/dT. A paramagnetic (PM) - ferromagnetic (FM) phase transition, is observed in this figure at TC = 46.17 K. Fig. 10 presents the susceptibility evolution and the magnetic hysteresis curve of the ZrTe3O8:7%CuO sample measured at 10 K temperature is plotted in Fig. 11.

In the paramagnetic region (above TC), the susceptibility was noted to follow the Curie– Weiss law defined by the following relation [28] χ =



from 10 to 300 K. Curie constant



C and Weiss θ were obtained by linear fitting χ-1 in this temperature range. Table 5 collects the characteristics of this compound: constant of Curie C, temperature of Weiss θ and 

effective moment μ  . The intersection point with the horizontal axis gives the value of θ. The slope gives the value of C. According to the Curie constant, we deduce the experimental 

effective moment μ  for the titled compound from the following relation (1): C =

  ( ) !"

=

 !"

μ# 



μ  = (√8C)μ'

(1)

Where kB is the Boltzmann constant (1.38016 10-16 erg k-1), N is the Avogadro's number (6.0221 × 1023 mol-1) and µ B is the Bohr magnetron (µ B = 9.27 10-21 emu). The ZrTe3O8:7%CuO contains one magnetic ion Cu2+ (S = 1/2, g = 2), the theoretical effective moment has been calculated based on the following relation: μ()  = g +S(S + 1)

(2)

Calculation leads to μ()é  = 1.73 μ' . Thus, the value of the experimental effective moment is closed to the theoretical value. This result confirms the singular contribution of Cu2+ to the magnetic sub-lattice. The positive value of θ indicates the ferromagnetic interaction between spins. Hysteresis loops was also measured between -5 to 5 Tesla at 10 K. The behavior of magnetization (M) versus the magnetic field (H) for the ZrTe3O8:7%CuO compound is shown in Fig. 11. An extremely strait hysteresis loop is observed, in agreement with the existence of a ferromagnetic order of these compound at T < TC. The isothermal magnetization at 10 K proves a hysteresis loop with a remnant magnetization around 0.09 μ' and a coercive field of 0.0225 Tesla. Thus, the ZrTe3O8:7%CuO ceramic is a soft magnetic material. 3.5. Dielectric measurements 3.5.1. Conductivity Studies The temperature dependence of the real (ε') and imaginary (ε″) parts of the dielectric permittivity for the ZrTe3O8:7%CuO compound at different frequencies were reported in Figs. 12 and 13, respectively. The compound behavior at high frequencies is perspicuous. (ε') and (ε″) values decrease with the increase of frequencies and reach a threshold value exhibiting a dispersive behavior . In the lower frequency region, the permittivity values are

relatively high reflecting blocking effects and can arise from the presence of various polarizations types [29-32]. The variation as a function of temperature of dielectric dissipation factor tangent (δ) = ε''(ω) / ε'(ω) is exposed in Fig. 14. The curves show a decrease of tangent (δ) as a function of frequency and an increase as a function of temperature. This increase is more and more intense indicating conductivity contribution at high temperatures. No phase transition has been observed in the explored temperature range. 3.5.2. Modulus Studies The (M  =f (ω)) plot given in Fig. 15 shows that M′ reaches a constant value: M∞ = (1/ε∞) at high frequencies caused by the relaxation process [33], while at low frequencies, it approaches zero indicating the insignificant effect of electrode polarization. The (M″=f (ω)) plot given in Fig. 16 illustrates two distinct regions. The region on the left of the relaxation peak, where ions are mobile over long distances and the region on the right where ions are confined in their potential wells. The peak is accompanied by a shoulder at low frequency which is related to grain boundary effects, and the well-defined one at higher frequency is associated to bulk effects. The modulus peak maximum shifts to higher frequencies with increasing temperatures. 3.5.3. Impedance spectroscopy and equivalent circuit The complex impedance parameters were expressed as: Z* = Z′-jZ″, giving data of both resistive (real part Z′) and reactive (imaginary part Z″) components [34-36]. To study the characteristics of ZrTe3O8:7%CuO ceramic, we chose to represent the imaginary part (-Z″) according to the real part Z′ of the complex impedance in a frequency domain extending from 209 Hz to 4.85 MHz and in domain temperatures between 293–843 K. The various complex impedance diagrams are shown in Fig. 17. Temperature increase is classically accompanied by resistance decrease, indicating that the conduction mechanism is thermally activated [37,38]. The complex impedance curves show semi-circle arcs that are not centered on the real axis so that cannot follow a Debye model but rather accord with a Cole–Cole model [39]. Assumed equivalent circuit allows the establishment of correlations between electrochemical system parameters and characteristic impedance elements. Fig. 18 shows the Simulate Nyquist plot with the equivalent circuit elements at 713 K for ZrTe3O8:7%CuO. The diagrams form implies that electric response is composed of two semicircles. The proposed circuit is successfully modeled by a series combination of two parallel combinations of resistance Ri and constant phase element CPEi, with R the polarization

resistance (bulk resistance) and CPE the complex element; constant phase element (capacity of the fractal interface). The impedance of the capacity of the fractal interface CPE is ZCPE = 1/A0(iω)α [40]. The real and imaginary components of the whole impedance of this circuit were calculated according to the following expressions: :; 12# 345 cos 9 = + 1> 2 0 = # :; :; 91 + 1> 34 5 cos 9 2 == + (1> 34 5 sin 9 2 =)# :; 12# 345 sin 9 = 2 0 = # :; :; 91 + 1> 34 5 cos 9 2 == + (1> 34 5 sin 9 2 =)# The good conformity of calculated lines with the experimental data indicates that the suggested equivalent circuit describes well the pellet–electrolyte interface. Fitted values (grain, grain boundary) parameters, obtained from the Zview software for the temperature 713 K, are listed in Table 6. The grain boundary conductivity influence in the total conductivity can be evaluated via the blocking factor (α) defined from the impedance diagram parameters as [41]: α = (A

A

A

=A

B A )

CDC

Where R1 and R2 are grain and grain boundary resistivity, respectively. The blocking factor (α) is less than 1 thus confirming the choice of the Cole-Cole model of ZrTe3O8:7%CuO. Conclusion In summary, the ceramic ZrTe3O8:7%CuO has been successfully synthesized by solid state reaction technique. It crystallizes in the cubic space group Ia3. The structure can be described by interconnected closed chains of Te-Oax-Te linked to Zr/CuO6 octahedra. In addition, studies by FTIR transmittance spectra and spectroscopy Raman were performed on the ceramic ZrTe3O8:7%CuO to confirm, in the first hand, the presence Te-O relative vibration bands and the presence of Te-O-Zr/Cu bridges. A broad peak observed in the optical band edge in the UV, which is related to the electronic transfers caused by the legend field splitting of d levels. Magnetic measurements reveal the occurrence of weak ferromagnetism behavior at low temperature for this ceramic (46.172 K). The magnetic susceptibility follows the Curie Weiss law, characterized by positive Weiss constants indicating the ferromagnetic interaction between spins. Dielectric and conductivity behaviors of doped ZrTe3O8 ceramic

were investigated using impedance spectroscopy. Increase in dielectric permittivity and dielectric loss was observed as a function of temperature. The Cole-Cole plot was successfully modeled by equivalent circuit consisting on a series combination of two parallel combinations of resistance Ri and constant phase element CPEi.

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Table 6

R1 (Ω)

R2 (Ω)

Q1 (10-9F)

Q2 (10-9F)

α1

α2

88000

399000

1.295

1.350

0.855

0.895

Table 1 Formula

ZrTe3O8:7%Cu

Temperature (K)

293

Space group

I a3ത

a (Å)

11.328(3)

V(Å3)

1453.96(7)

Z

8

Diffractometer

Bruker Apex II

Radiation (Å)

Cu Kα1 and Kα2 (λ = 1.5406 et 1.5444 Å)

2θ Range of refinement (°) Number of structural variables Number of profile parameters

19.9395- 80. 8131 158 52

RP (%)

5.88

Rwp (%)

8.02

Rexp (%)

5.54

χ2 (%)

2.09

Rbragg (%)

5.93

RF (%)

5.31

Table 2

Atoms

Site

x

y

z

Te

24d

0

0.25

0.0434(3)

Zr

8a

0.25

0.25

0.25

Cu

8a

0.25

0.25

0.25

O1

16c

0.0790(2)

0.0790(2)

0.0790(2)

O2

48e

0.1140(3)

0.3128(2)

0.1420(2)

Table 3 Compounds

a(Å)

ZrTe3O8

11.308(1) 11.328(3)

ZrTe3O8:7%Cu

Te-O2 (Å)

Te-O1 (Å)

Zr -O2 (Å)

1.858(2)

2.166(7)

2.073(2)

1.850(2)

2.172(2)

2.092(2)

Table 4 Assignments 

ν ν  ν   ν ν(Te-O-Te) ν(Zr-O)

ZrTe3O8:7%Cu 787 (F) 704(m) 666(m) 486(m) 415(m)

Table 5 Compound ZrTe3O8:7%Cu

C (emu.K.mol-1.Oe-1) 0.272(1)



θ

μ (μ )

TC (K)

17.371(1)

1.475

46.172

Highlights - The ceramic crystallized at room temperature in the cubic fluorite structure (Ia3ത). - The Zr/CuO6 octahedra are inserted into TeO4E chains ensuring the stability of the structure by Zr/Cu -O-Te bonding contacts. - The magnetic results reveal the appearance of a weak ferromagnetic behavior at low temperature (TC = 46.172 K). - At all the frequencies, (ε′), (ε″) and tan (δ) increase linearly with rise in temperature. - The equivalent circuit model is composed of a series combination of two parallel combinations of resistance Ri and constant phase element CPEi. -.

Declaration of interest statement Synthesis of a new dopped ceramic based on a transition metal possessing important physical properties applied in mobile communication systems. This family ceramics adopt generally the Ia3ത cubic arrangement and were considered as portentous dielectric materials for low temperature co-fired ceramics (LTCC) applications. Now, dielectric ceramics for use in resonators at microwave frequency have been paid increasing regard due to the fast growth of mobile communication systems such as cellular phone and global positioning systems.