Structural and impedance spectroscopy properties of La0.8Ba0.1Ca0.1Mn1−xRuxO3 perovskites

Author’s Accepted Manuscript STRUCTURAL AND IMPEDANCE SPECTROSCOPY PROPERTIES OF La0.8Ba0.1Ca0.1Mn1-xRuxO3 PEROVSKITES M. Chebaane, N. Talbi, A. Dhahri, M. Oumezzine, K. Khirouni www.elsevier.com/locate/jmmm

PII: DOI: Reference:

S0304-8853(16)32822-0 http://dx.doi.org/10.1016/j.jmmm.2016.10.153 MAGMA62066

To appear in: Journal of Magnetism and Magnetic Materials Received date: 8 April 2016 Revised date: 26 September 2016 Accepted date: 28 October 2016 Cite this article as: M. Chebaane, N. Talbi, A. Dhahri, M. Oumezzine and K. Khirouni, STRUCTURAL AND IMPEDANCE SPECTROSCOPY PROPERTIES OF La 0.8Ba0.1Ca0.1Mn1-xRuxO3 PEROVSKITES, Journal of Magnetism and Magnetic Materials, http://dx.doi.org/10.1016/j.jmmm.2016.10.153 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. 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.

STRUCTURAL AND IMPEDANCE SPECTROSCOPY PROPERTIES OF La0.8Ba0.1Ca0.1Mn1-xRuxO3 PEROVSKITES

M. Chebaane1*, N.Talbi2, A. Dhahri1, M. Oumezzine1, K.Khirouni2

1

Laboratory of Physical Chemistry of Materials, Department of Physics, Faculty of Sciences of Monastir, University of Monastir, 5019 Monastir, Tunisia

2

Laboratoire de Physique des matériaux et nanomatériaux appliqués à l'environnement, Faculté des

Sciences de Gabes, Département de Physique, 6079 Gabes, Tunisie

*

Corresponding author. Tel.: +216 73 500278; fax: +216 73 500280: [email protected] (M.Chebaane)

Abstract Polycrystalline samples La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x= 0 and 0.075) were prepared by sol-gelbased Pechini method. The X ray diffraction study has shown that all the samples exhibit a single phase with rhombohedral structure (space group R ̅ c, no. 167). The complex impedance has been investigated in the temperature range 160–320 K and in the frequency range 40 Hz–1 MHz. The imaginary part of the complex impedance (Z'') frequency dependence revealed one relaxation peak. The Cole-Cole plots of the impedance values exhibited a semi –circular arc that can be described by an R1+ (R2//ZCPE) electrical equivalent circuit. The conductance spectra have been investigated by the Jonscher universal power law: G(ω)= GDC +Aωn, where ω is the frequency of the ac field, and n is the exponent. The activation energy obtained both from the conductance and from time relaxation analyses are

very similar, and hence the relaxation process may be attributed to the same type of charge carriers.

Keywords: Perovskite; ac conductivity; Relaxation process

1. Introduction The family of doped perovskite manganites with a generic formula Ln1-xAxMnO3 (Ln: La, Pr, Nd, etc. and A: Ba, Sr, Ca, etc.) has attracted tremendous attention in the recent past due to its impressive physical properties and potential application. They can be used as magnetoresistive transducers, magnetic sensors, computer memory systems, magnetic refrigerants and infrared detectors [1, 2]. From the applications perspective, interest in these materials arose initially from their potential applications in hard disks, magnetic sensors, spinelectronic devices, and magnetic refrigerants [3, 4]. For this reason, it is essential to study their electric and magnetic properties. In the mixedvalence manganites, the rich electric and magnetic properties have been explained by means of the double exchange (DE) interaction theory [5], which considers the ferromagnetic (FM) coupling and the eg electron shopping through Mn3+-O2--Mn4+network. The motion of the eg electron can be strongly influenced by the average ionic radius of the A and/or B- site exhibits a close relationship between the bending of the Mn-O-Mn bond angle and the narrowing of the electronic bandwidth[6,7]. The double exchange (DE) theory basically explains the simultaneous occurrence of the paramagnetic - ferromagnetic (PM-FM) and metallic semiconductor (M-Sc) phase transitions for most hole-doped manganites, other illustrative mechanisms were used to explain the observations related to the physics properties of manganites materials. To our knowledge, few investigations were devoted to the study of the perovskite manganite.

The purpose of this work is to study the structural and electrical properties (material impedance, electrical relaxation process, conductance behavior, etc.) of La0.8Ba0.1Ca0.1Mn1-x RuxO3 (x= 0 and 0.075) system. Complex impedance spectroscopy (CIS) is an efficient and powerful tool whereby we have investigated electrical properties of our samples. Actually, the study of DC electrical conductance and AC conductance, give much more valuable information on the behavior of free and localized electric charge carriers. 2. Experimental details Ru-doped lanthanum manganites with nominal composition La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x= 0 and 0.075) were synthesized by the Pechini method. Stoichiometric amounts of La(NO3)3.6H2O,Ba(NO3)2,Ca(NO₃)₂, Mn(NO3)3.4H2O and Ru(NO)(NO3)3, and citric acid were dissolved in distilled water with adequate amount of ethylene glycol under thermal stirring. After a viscous resin was formed, the mixture was calcined to roughly 523 K and then ground in a mortar, followed by drying at 873 K for 24 h in air. As a final step, the powder was pressed into pellets of a few millimeters thick (~ 2 mm) and a diameter of about 1 cm by pressing under 10 tonnes / cm2 which are subsequently sintered respectively at 1073 K (36 h) and 1100 K (48 h) in order to obtain different crystalline phases. The structural characterization and refinement were achieved through respectively X-ray diffraction measurements (XRD) using a “Panalytical X'Pert Pro” diffractometer and the Rietveld analysis of the powder XRD data with the FULLPROF software [8]. The ac impedance of the samples was measured between 160 K and 320 K, and the frequency 40 Hz up to 1 MHz, using an Agilent 4294A Precision Impedance Analyser. 3. Results and discussions 3.1. Microstructure analysis

Figure 1 Shows the SEM micrographs patterns for our samples (x = 0 and 0.075). The SEM photographs of La0.8Ba0.1Ca0.1Mn1-xRuxO3 compounds show a porous and homogeneous microstructure. We can also observe a unique chemical contrast corresponding to the manganite phase. Moreover, the microstructure of our samples appears to be sensitive to Ru substitution. As Ru content increased, the average grain size went up from 100 nm (for x= 0) to 114 nm (for x= 0.075) which is calculated from linear intercept method. Figure 2 shows room temperature XRD patterns of La0.8Ba0.1Ca0.1Mn1-xRuxO3 samples with x = 0 and 0.075. The diffraction peaks are sharp, indicating well crystallized phases. In agreement with SEM results, no impurity phases were detected within the X-ray diffraction limits. An enlarged scale of the most intense peak (104 Bragg reflections) shows a shift to smaller angles 2 values (see the inset of Figure 2), indicating that the cell parameters (and thus the unit cell volume) increases with increasing Ru content. In the interest of figuring out the crystalline structure of our samples, we calculated the Goldschmidt tolerance factor defined by [9]: √

(1)

where rA, rB and rO are respectively the average ionic radii of the A and B perovskite sites and oxygen anion. In fact, for tG close to unity we obtain a cubic perovskite structure and for (0.89
refined in the R ̅ c space group by the Rietveld method using the FULLPROF software. In this refinement the atomic positions are taken at 6a (0, 0, 1/4) for (La/Ba/Ca), 6b (0, 0, 0), for Mn and 18e (x, 0, 1/4) for O. Figure 3 gives the Rietveld refinement data of La0.8Ba0.1Ca0.1Mn1-x RuxO3 compounds showing a good agreement between observed and calculated profiles. The quality of the agreement is evaluated through the adequacy of the fit indicator 2. Detailed results of Rietveld refinement are listed in Table 1. One can see in this table that all the lattice parameters and the unit cell volume increase with increasing Ru content in the samples. This increase can be explained by the rise of average ionic radius of B site () due to the larger ionic radius of Ru3+ ion (

and

[10]).

In order to extract the average grain size from the X-ray diffraction data, we used the following formula: √

where

(2)

is the X-ray wavelength and IG is the crystallite size given by the Rietveld

refinement. When we introduced the ruthenium,

went up from 41 nm to 45 nm (see

Table 1). The difference between the grain size extracted from the X-ray diffraction data and the SEM micrographs is due to the fact that each particle observed by SEM is made of several crystallites [13]. 3.2. Electrical conductance studies Figure 4 presents the frequency dependence of the conductance at different temperatures, between 160 K and 320 K, for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075). The analysis of the electrical conductance gives important information about the transport of charge carriers (electrons / holes) predominating the conduction process in function of temperature and frequency. In manganites, the electrical conductance is mainly due to electrons hopping between ions of the same element in more than one valency state (Mn3+↔Mn4+). The charges

can migrate under the influence of the applied field which contributes to the electrical response of the system. According to the attempt made by Jonscher to explain the behavior of the electrical conductance [11] given in the equation (3), the total conductance G of our samples is the superposition of DC conductance (GDC) and the AC conductance (GAC): G(ω) = GDC + GAC = GDC +Aωn

(3)

where A is a pre-exponential factor which depends on the temperature and the exponent n is independent of frequency, but depends on the temperature and the type of the studied material. These curves are frequency-independent in the low frequency region (as shown by a plateau at low frequencies corresponding to the DC conductance GDC), followed by a sharp increase at high frequencies. It is clear in Figure 4 that this plateau becomes wider as the temperature increases. In this zone, we can observe from GDC spectrums the presence of an electrical transition from the metallic state (M) to the semiconductor state (Sc) at the temperature TM-Sc. TM-SC values decreases from 220 K for x = 0 to 180 K for x = 0.075. The same behavior was observed in others works [12,13]. This reduction(TM-Sc.) can be explained by the reduction of the oneelectron bandwidth W given by: W

cos d Mn O

where  

(4)

3,5



1 180  θ Mn OMn 2

 is the average tilt angle in the bond plot and

d Mn O is the

average distance Mn-O. The variation of W with x is reported in Table 1. In fact, narrowing the bandwidth reduces the overlap between the 2p orbitals of O2- and 3d orbitals of Mn, which greatly weakens the influence of Mn 3+- O2- -Mn 4+ interactions and consequently the decrease in temperature TM-Sc. This can be explained differently:

Generally, for a charge transfer-type semiconductor or insulator, the gap energy Eg can be given by Eg=-W, where  is the charge transfer energy and W is the bandwidth of eg electrons. Actually,  varies little in the manganite systems R1-x AxMnO3 and the bandwidth W becomes the important factor regulating the energy band gap Eg [14]. Thus, the decrease of W increases the band gap Eg and leads to a lower metal-semiconductor transition temperature TM-Sc. We can notice as well from Figure 5 and increase in the GDC conductance with increasing Ru content. This result indicates that the conduction process is more active for x = 0.075 than for x = 0. This can be mainly attributed to the increase of the grain size with higher concentrations of Ru. Actually, when the average grain size goes up, the number of grain boundaries goes down and therefore the compound x = 0.075 is more conductive than x = 0. The plots of log(GT) against 1/T shown in Figure 6 for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075), where GDC is the value of the low frequency conductance (f = 40 Hz) and T the absolute temperature, are linear over a wide temperature range. The linear variation for high temperatures proves that the conductance is overpowered by small polaron hopping (Small Polaron Hopping, SPH) thermally activated. DC conductance was well fitted, at high temperature range, by the Mott and Davis law [15] which describes small polaron hopping (SPH): (

)

(5)

Where B is a pre-exponential factor, Ea is the activation energy, T is the absolute temperature and kB is the Boltzman constant. The values of activation energy estimated decreases of Ea = 203 meV for x = 0 to Ea = 87 meV for x = 0.075 which leads directly that the compound x = 0.075 more conductive than x = 0.

For higher frequencies, beyond the plateau, a second behavior is characterized by the linear variation of the GAC conductance versus frequency (logarithmic scale). This variation is known as the Universal Dynamic Response (UDR)) [16] in which the AC conductance, at high frequency, can be described by the following power law [17]: GAC = Aωn, where A and n are constants depending on the conduction process. According to Funke [18], for the alternative conductance (GAC), n ≤ 1 means that the electron hopping involves a translational motion between ions and it is carried out at long distance or VRH as "variable-range hopping" whereas n> 1 means that the electron hopping is between neighbouring ions. The exponent n is frequency independent, but it depends on the temperature and the type of material. The curves of the electric conductance versus frequency at various temperatures of La0.8Ba0.1Ca0.1Mn1-xRuxO3 compounds (x = 0 and 0.075) has been fitted using the law of Jonscher (red lines of the Figure 4) given by Eq.(3). The results of this adjustment are summarized in Table 2. The quality of fit is generally evaluated by comparing the squared coefficient of linear correlation coefficient (R2) obtained for each compound. If we compare the experimental measurements and the fit of these measures according to the model of Eq. (3), a very good agreement is noticed in the entire frequency range. For both compounds, we can conclude from Table 2 that the exponent n decreases with the increase of the temperature below TM-Sc, whereas, above TM-Sc, n increases with the rise of temperature. We also can note that the values of the exponent n obtained for x = 0.075 are all higher than those obtained for x = 0. This may be related to the increase of the grain size when the substitution rate of Ru increases, which means that “the hopping “of electrons between ions is better for x = 0 and therefore the compound x = 0.075 is more conductive. 3.3. Complex impedance analysis

Complex impedance spectroscopy (CIS) is a powerful technique to study the electrical properties of polycrystalline ceramics over a wide range of frequency and temperature. We have depicted in Figure 7 the Nyquist plots of samples of the present investigation over a wide range of frequency and at different temperatures. Those impedance spectrums are in fact compound of semicircles shifted from the origin and are not centred on the real axis and whose maxima increase below TM-Sc and go down above TM-Sc with increasing temperature. Further after, in order to interpret such a diagram, the impedance data were fitted to an equivalent circuit via Zview software (red solid line in Figure 7). The equivalent circuit configuration for our samples (see the inset of Figure 7) is composed by a serial association of a grain resistance Rg with a resistance Rgb (respectively R1: bulk resistance and R2: grain boundary resistance, calculated both from the intercepts on the real part of the Z’ axis) associated in parallel with constant phase element impedance (ZCPE). The impedance of CPE is given by this relation [19-20]: (6) where T (CPE-T) indicates the value of capacitance of the CPE element (expressed in Farad units), and p(P-CPE) is the factor exponent (0 ≤ p ≤ 1). According to P. Zoltowski [21] and Z. Stoynov and al. [22], the factor p represents the capacitive nature of the element: if p = 1, the element is an ideal capacitor, it behaves as an RC circuit called Warburg impedance if p = 0.5 and a frequency independent ohmic resistor if p = 0. T and p can depend of temperature. We can reveal the real and imaginary components of the impedance related to the equivalent circuit using Eq. (6):

(

)

(

)

(7)

(

)

(

)

(8)

The parameters for the circuit elements (Rg, Rgb, T and p) were extracted for each temperature. These results showed that the grain resistance Rg is too weak if we compare it to the grain boundaries resistance Rgb. Therefore, total resistance RT (equal to the sum of grain and grain boundaries ones [23, 24]) is approximately dominated by the grain boundaries component Rgb. If we take a look at the Figure 8, we can notice that the curves exhibit an increase of Rgb below TM-Sc and then fall above TM-Sc with the rise of temperature. Similar behavior has been reported for other studies in which R.Bellouz and al [25] have worked with different perovskite systems. The evolution of log Rgb vs. 1/T is shown in Figure 9, where we achieved a linear fit for temperatures higher than TM-Sc (the red solid lines) and afterward, we determined the values of the activation energy Ea.. This energy dropped from 176 meV to 69 meV when increasing the Ru rate indicating an improvement in the conduction process. Figure 10 and insets show the variation of the real part of the impedance (Z') as a function of frequency at different temperatures for La0.8Ba0.1Ca0.1Mn1-xRuxO3 compounds (x = 0 and 0.075). It is found that Z' increases with increasing temperature below TM-Sc . However, above TM-Sc, Z' decreases with increasing temperature (inset of Figure 10). These spectrums also reveal that the compound x = 0.075 has the lowest real part Z' comparing with the compound x = 0. So the conductivity of materials increases with the rise of Ru content as reported in the interpretation of previous results in the electrical conductance. These curves are manifested by a uniform conduct in a certain range of frequencies, beyond this, a decreasing behavior will occur that will eventually stabilize for high frequencies. Furthermore, we can notice here that the values of Z' are typically very high at low temperatures and then fall progressively with increasing the temperature. As Z' values

converge to high frequencies, it indicates the presence of a possible release of the space charge due to the reduction in barrier properties of the material with the rise of temperature [26, 27]. At high frequencies, Z' is also independent of temperature. This can be interpreted by the presence of a space charge polarization. The behavior of Z' observed for our samples at low and high frequencies is in good agreement with the results reported in the literature [28, 29]. The variation of Z″ with frequency at different temperatures for La0.8Ba0.1Ca0.1Mn1-xRuxO3 compounds (x = 0 and 0.075) is depicted in Figure 11 and its insets. The spectra are characterized by appearance of peaks, which shift to low frequencies below TM-Sc (respectively towards high frequencies above TM-Sc) with increasing temperature. This behavior describes the type and the strength of electrical relaxation phenomenon in the material in both compounds. The position of these peaks allows the extraction of the relaxation frequency value (fmax) and the relaxation time (τ) using the relation: τ = 1/2πfmax

(9)

The temperature dependent characteristics of τ follow the Arrhenius relation as mentioned below: (10) where Ea is the activation energy. Figure 12 shows the variation of log(τ) vs.1/T. For high temperatures, this variation is linear and the values of the estimated activation energy went down from Ea = 166 meV for x = 0 to Ea = 64 meV for x = 0.075. The activation energy value is in good agreement with that deduced previously from the electrical conductance analysis and the Nyquist plots analysis, which means that the relaxation process and the electrical conductivity are ascribed to the same defect.

4. Conclusion To sum up, the effects of Ru substitution for the Mn site in La0.8Ba0.1Ca0.1MnO3 compound are investigated in terms of structural characteristics and electrical properties using impedance spectroscopy technique over a wide range of temperature (160 K–320 K) and frequency(40 Hz–106 Hz). We have found that all samples crystallize in the rhombohedral structure (R ̅ space group) with an increase in unit cell volume. Moreover, for both samples, electrical investigation shows a metallic-semiconductor transition temperature TM-Sc. The study of DC conductance reveals that electronic conduction is found to be overpowered by hopping of small polarons (SPH) thermally activated, where the estimated activation energy was lower for x=0.075 than for x=0. Such activation energy was also deduced from Nyquist plots analysis and thereafter from the complex impedance analysis that proves the presence of an electrical relaxation phenomenon in both compounds. Thus, all those studies confirm that the compound x=0.075 is more conductive than the compound x=0.

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[7] Z.B.Guo, N. Zhang, W.P.Ding, W.Yang, Solid. State.commun. 100 (1996) 769. [8] T. Roisnel, J. Rodriguez-Carvajal, Computer Program FULLPROF, LLBLCSIM. May 2003. [9] V.M. Goldschmit, Geochem Verteil Elem 7, (1927) 8. [10] R.D. Shannon, C.T. Prewitt, Acta Crystallogr. Sect. B 25, (1969) 925. [11] A.K. Jonscher, Universal Relaxation Law, Chelsea Dielectric Press, London, 1996. [12] W. A. Harrison, The Electronic Structure and Properties of Solids, Freeman, San Francisco, 1980. [13] Ma. Oumezzine, S. Kallel, O. Peña, N. Kallel, T. Guizouarn, F. Gouttefangeas, M. Oumezzine, J. Alloys Comp. 582 (2014) 640–646. [14] L. Seetha Lakshmi, V. Sridharan, D.V. Natarajan, Rajeev Rawat, Sharat Chandra, V. Sankara Sastry, T.S. Radhakrishnan, Journal of Magnetism and Magnetic Materials 279 (2004) 41–50. [15] N.F. Mott, E.A. Davis, Electronic Process in Non Crystalline Materials, Clarendon Press, Oxford, 1979. [16] A.K.Jonscher, the « Universal » dielevtric responce, Nature, 267( 1977) 673 . [17] A.K. Jonscher: Dielectric Relaxation in Solid. Chelsea Dielectrics Press, London (1983). [18] K. Funke, Prog. Solid State Chem. 22 (1993) 111. [19] P. Córdoba-Torres, T.J. Mesquita, O. Devos, B. Tribollet, V. Roche, R.P. Nogueira, J. Electrochim. Acta 72 (2012) 172–178. [20] B. Hirschorn, M.E. Orazema, B. Tribollet, V. Vivier, I. Frateur, M. Musiani, J. Electrochim. Acta, 55 (2010) 6218–6227. [21] P. Zoltowski, J. Electroanal. Chem. 443 (1998) 149–154. [22] Z. Stoynov, D. Vladikova, Differential Impedance Analysis, Marin Drinov Academic Publishing House, (2005).

[23] M. Nadeem, M.J. Akhtar, A.Y. Khan, Solid State Commun. 134 (2005) 431. [24] M. Nadeem, M.J. Akhtar, A.Y. Khan, R. Shaheen, M.N. Hoque, Chem. Phys. Lett. 366 (2002) 433. [25] R. Bellouz, S. Kallel, K. Khirouni, O. Pena, M. Oumezzine, J. Ceramics International 41 (2015) 1929–1936. [26] J. Maier, J. European Ceram. Soc. 24 (2004) 1343. [27] S. Sen, S.K. Mishra, S.K. Das, A. Tarafdar, J. Alloys Compounds 453 (2008) 395. [28] H. Rahmouni, A. Selmi, K. Khirouni, N. Kallel, J. Alloys Comp. 533 (2012) 93. [29] S. Khadhraoui, A. Triki, S. Hcini, S. Zemni, M. Oumezzine, Journal of Magnetism and Magnetic Materials 371 (2014) 69.

Fig 1: SEM images of La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) samples Fig 2: XRD patterns for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) powders. All peaks of the manganite phase are indexed in the rhombohedral R ̅ c symmetry. Inset: XRD profiles of the most intense peak (Bragg reflections 1 0 4) which shifts to lower 2θ values as Ru content increases. Fig 3: X-ray diffraction pattern and the corresponding Rietveld refinement of the La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) samples. Observed (Yobs) and calculated (Ycalc) patterns are compared (blue line). The vertical ticks show the positions of the calculated Bragg reflections Fig 4: Electrical conductance versus frequency for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) at different temperatures. Red solid lines represent the fitting to the experimental data using the universal Jonscher power law. Fig 5: The temperature dependence of DC conductance GDC for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) compounds.

Fig 6: Variation of the log(GDCT) as a function of (1/T) for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) samples. Red solid line is the linear fit for our data using SPH model. Fig 7: Complex impedance spectra at given temperatures for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) compounds with electrical equivalent circuit (see the inset), the solid line is a fit of the experimental data. Fig 8: Variation of Rgb with temperature extracted from complex impedance spectra for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) compounds. Fig 9: Variation of log(Rgb) vs. (1/T) for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) samples. Fig 10: Variation of real part of the impedance (Z') for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) nanocrystalline manganites as a function of frequency for different temperatures. Fig 11: Variation of imaginary part of the impedance (Z'') for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) compounds as a function of frequency for different temperatures. Fig 12: Variation of the log(τ) vs. (1/T) for the La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) compounds. Red solid line is the linear fit for our data.

Table 1 Refined structural parameters of La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) at RT (R ̅ c space group): V: cell volume; Biso is the overall isotropic thermal parameter; d(Mn, Ru-O): average bond lengths between (Mn, Ru) and O; θ(Mn, Ru-O-Mn, Ru): average bond angles; W: bandwidth; tG: Goldschmidt tolerance factor;

: average grain size. Rp, Rwp and RF are the

agreement factors for the profiles, the weighted profiles and the structure factors; χ2 is the goodness of fit. The numbers in parentheses are estimated standard deviations to the last significant digit.

x

0

0.075

R̅c

R̅c

a (Å)

5.4531 (3)

5.4602 (2)

c (Å)

13.432 (1)

13.4476 (8)

V (Å3)

345.90 (4)

347.21 (3)

(La, Ba, Ca) Biso (Å2)

1.72 (7)

1.83 (3)

(Mn, Ru) Biso (Å2)

0.347 (0)

0.10 (4)

(O) x

0.520 (4)

0.52529 (0)

(O) Biso (Å2)

1.4 (2)

2.30 (1)

d(Mn, Ru-O) (Å)

1.9346 (0)

1.9389 (0)

θ(Mn, Ru-O-Mn, Ru) (°)

173.54 (5)

171.832 (8)

W(10-2) (u.a.)

9.91

9.82

tG

0.972

0.971

41

45

Rwp (%)

6.35

6.69

Rp (%)

4.74

4.91

RF (%)

9.76

4.18

χ2 (%)

2.54

2.81

Space group Cell parameters

Atoms

Structural parameters

(nm)

Agreement factors

Table 2: Values of the DC conductance, the constant (A) ,the exponent (n) and the squared coefficient of linear correlation coefficient (R2), for La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x = 0 and 0.075) compounds, determined at different temperature. x=0 GDC (S)×10-

x = 0.075

7

A×10-11

160

2.030

1.511

0.864

0.999

8.572

180

0.859

1.845

0.775

0.999

200

0.376

2.105

0.730

220

0.269

2.042

240

6.145

260

11.264

T (K)

n

R2

1.0458

0.875

0.996

7.149

1.2465

0.795

0.995

0.999

11.81

0.7004

0.854

0.994

0.709

0.999

16.013

0.1792

0.972

0.993

0.562

1.025

0.999

22.27

0.0671

1.054

0.992

0.282

1.056

0.999

26.847

0.0612

1.075

0.971

n

R2

GDC (S)×10-6

A×10-10

280

18.539

0.393

1.057

0.999

35.173

0.0499

1.093

0.973

300

31.752

0.388

1.061

0.974

40.415

0.0042

1.278

0.988

320

54.246

0.346

1.065

0.979

48.822

0.0020

1.329

0.982

Highlights 

Polycrystalline samples La0.8Ba0.1Ca0.1Mn1-x RuxO3 were prepared using the Pechini sol-gel method.



The X ray diffraction study has shown that all the samples exhibit a single phase with rhombohedral structure.



Conductance spectrum of doped samples obeys to the Jonscher law.



This study was supported by the complex impedance analysis.

Fig 1

104

Fig 2

4

2,4x10

x=0 x = 0.075

4

I (u.a.)

1,8x10

I (u.a.)

x= 0 x= 0.075

4

1,2x10

3

6,0x10

33,0

2 (°)

33,5

34,0

80

100

238

324

60

220

40

134

20

214

0

32,5

2 (°)

202 024

012

0,0 32,0

120

Fig 3

x=0

x=0.075

Fig 4

-5

x= 0

10

Conductance (S)

320 K

-6

10

160 K -7

10

220 K 0

10

1

10

2

10

3

10

4

10

5

10

6

10

f (Hz) 1E-4

x= 0.075

Conductance (S)

320 K

1E-5

160 K 180 K

0

10

1

10

2

10

3

10

f (Hz)

4

10

5

10

6

10

Fig 5

1E-3

x= 0 x= 0.075

1E-4

TM-Sc= 180 K

GDC (S)

1E-5 1E-6

TM-Sc= 220 K 1E-7 1E-8 1E-9 160

200

240

T (K)

280

320

Fig 6

10

log(GDCT) (S. K)

x= 0 x= 0.075 Fit

Ea= 87 meV

-2

-3

10

-4

10

Ea= 203 meV

-5

10

-6

10

-3

3,0x10

-3

-3

4,0x10

5,0x10 -1

1/T (K )

-3

6,0x10

Fig 7

7

4,5x10

x=0 1,6x10

6

Z''()

3,6x10

1,2x10

6

8,0x10

5

4,0x10

5

160 K 180 K 200 K 220 K Fit

x=0 240 K 260 K 280 K 300 K 320 K Fit

7

Z''( )

7

2,7x10

0,0 0,0

4,0x10

5

8,0x10

7

5

1,2x10

6

1,6x10

6

Z'()

1,8x10

6

9,0x10

0,0 0,0

6

7

9,0x10

7

2,7x10

3,6x10

7

4,5x10

Z'( )

5

1,6x10

7

1,8x10

x = 0.075

4

9,0x10

x = 0.075 200 K 220 K 240 K 260 K 280 K 300 K 320 K Fit

4

6,0x10

5

Z''( )

1,2x10

4

Z''( )

3,0x10

4

8,0x10

4

0,0

3,0x10

4

6,0x10

4

9,0x10

Z'( )

4

4,0x10

0,0

160 K 180 K Fit 4

4,0x10

4

8,0x10

Z'( )

5

1,2x10

5

1,6x10

Fig 8

5

1,6x10

x = 0.075

7

4x10

x=0

7

3x10 5

Rgb(

1,2x10

7

2x10

Rgb ()

7

1x10 4

8,0x10

0 160

200

240

280

320

T (K) 4

4,0x10

160

200

240

T (K)

280

320

Fig 9

7

10

x=0 x=0.075 Linear Fit

6

log(Rgb)

10

Ea = 176 meV

5

10

Ea = 69 meV 4

10

-3

3,6x10

-3

-3

4,5x10

5,4x10 -1

1/T(K )

-3

6,3x10

Fig 10

x= 0

7

4x10

6

240 K 260 K 280 K 300 K 320 K

1,6x10

6

1,2x10

Z' ()

7

3x10

5

8,0x10

5

Z'

4,0x10

7

2x10

0,0 2

3

10

10

4

5

10

10

6

10

f (Hz)

160 K 180 K 200 K 220 K

7

1x10

0 2

3

10

4

10

5

10

6

10

10

f (Hz) 5

1,6x10

x= 0.075 160 K 180 K

5

200 K 220 K 240 K 260 K 280 K 300 K 320 K

4

9,0x10

4

8,0x10

4

Z' ()

Z'(

1,2x10

4

4,0x10

6,0x10

4

3,0x10

2

10

3

10

4

10

5

10

6

10

f (Hz)

0,0 2

10

3

10

f (Hz)

4

10

5

10

6

10

Fig 11

x= 0 7

1,6x10

Z'' ()

7

1,2x10

Z''(

240 K 260 K 280 K 300 K 320 K

5

6,0x10

5

4,0x10

5

2,0x10

6

0,0

8,0x10

2

3

10

4

10

10

5

6

10

10

f (Hz)

160 K 180 K 200 K 220 K

6

4,0x10

2

3

10

4

10

5

10

6

10

10

7

10

8

10

f (Hz) x= 0.075 4

4

4x10

6,0x10

200 K 220 K 240 K

4

260 K 280 K

Z''()

Z''(

3x10

4

4,0x10

300 K

4

2x10

320 K

4

1x10

0

4

2

2,0x10

10

3

4

10

10

5

10

6

10

f (Hz)

160 K 180 K 0,0 0

10

1

10

2

10

3

10

f (Hz)

4

10

5

10

6

10

Fig 12

-3

log( ) (s)

10

x= 0 Fit

-4

10

Ea= 166 meV -5

10

-6

10

-3

3,2x10

-3

4,0x10

-3

4,8x10

-3

6,4x10

-3

6,4x10

5,6x10

-3

-1

1/T(K ) -5

10

x= 0.075

log(  (s)

Fit

Ea= 64 meV -6

10

-3

3,2x10

-3

4,0x10

-3

4,8x10

-1

1/T(K )

5,6x10

-3