Structural and phase transition of mg doped on mn site in la0 7sr0 3mno3 bulk nanostructured perovskite characterised through online ultrasonic technique

Structural and phase transition of Mg-doped on Mn-site in La 0.7 Sr 0.3 MnO 3bulk/nanostructured perovskite characterised through online ultrasonic technique Somasundaram Praveenkumar1,

Structural and phase transition of Mg-doped on Mn-site in La0.7Sr0.3MnO3 bulk/

nanostructured perovskite characterised through online ultrasonic technique

Somasundaram Praveenkumar, Kathiresan Sakthipandi, Mathu Sridharpanday,

Mohanraj Selvam, Arumugam Karthik, Srinivasan Surendhiran, Nallaiyan Palanivelu,

Gurusamy Raj kumar, Venkatachalam Rajendran

PII: S1026-9185(16)30024-5

DOI: 10.1016/j.sajce.2016.12.001

Reference: SAJCE 15

To appear in: South African Journal of Chemical Engineering

Received Date: 23 May 2016

Revised Date: 21 November 2016

Accepted Date: 19 December 2016

Please cite this article as: Praveenkumar, S., Sakthipandi, K., Sridharpanday, M., Selvam, M., Karthik, A., Surendhiran, S., Palanivelu, N., Raj kumar, G., Rajendran, V., Structural and phase transition

of Mg-doped on Mn-site in La0.7Sr0.3MnO3 bulk/nanostructured perovskite characterised through

online ultrasonic technique, South African Journal of Chemical Engineering (2017), doi: 10.1016/

j.sajce.2016.12.001.

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TITLE: Structural and phase transition of Mg-doped on Mn-site in La 0.7 Sr 0.3 MnO 3

bulk/nanostructured perovskite characterised through online ultrasonic

technique

Manuscript ID: SAJCE_2016_42

S No Name Institution Email ID

7 Nallaiyan Palanivelu Arignar Anna Government

Arts College for Men, Namakkal

veerajedran@gmail.com

Structural and phase transition of Mg-doped on Mn-site in La 0.7 Sr 0.3 MnO 3

bulk/nanostructured perovskite characterised through online ultrasonic technique

Somasundaram Praveenkumar1, Kathiresan Sakthipandi, Mathu Sridharpanday, Mohanraj Selvam, Arumugam Karthik, Srinivasan Surendhiran, Nallaiyan Palanivelu2, Venkatachalam Rajendran* and Gurusamy Raj kumar3

Bulk and nanoshaped perovskite manganite materials were blended to form samples of

La 0.7 Sr 0.3 Mg 1-x Mn x O 3(LSMMO) with x = 0.05, 0.075, and 0.100 employing solid state and

sonochemical methods, respectively The well-formed LSMMO component was characterized

by comprehensive characterization techniques and rhombohedral structure was observed The mean size of the bulk and nano LSMMO manganite perovskites ranges between 260–850 nm and 23–86 nm, respectively The structural and phase transition of the manganite perovskites are explored by on-line ultrasonic velocity and attenuation measurementsbetween 300 and 400

K A deliberate change in the ultrasonic velocity, attenuationand elastic moduli shows an abnormal behavior with temperature in perovskites and was associated with the occurrence of

ferromagnetic-paramagnetic (FM-PM) transition temperature (TC) In addition, the shifts in T C magnitude and width by increase in x are used to study the etiquette of TC and the change in the nanostructure of the bulk perovskites

Keywords: Abnormal behavior; Ultrasonic measurements; Phase transition; Elastic properties; perovskites

Several efforts have been made to examine the CMR associated with the lattice deformation and charge ordering (CO) of the crucial Mn–O–Mn network by doping the divalent alkaline atoms such as Ca, Sr, Ba, and Pb [8–10] at the A-site in the manganite perovskite It has been revealed that the magnetic and transport properties of manganite perovskites are devastated by the substitution of Mn at the B-site by any other atom [11–14] The substitution on Mn-site affects the Mn3+–Mn4+ ratio and hence, the exchange interaction of

Mn3+–Mn4+occurs The mismatch of ionic radius between Mn and substituted ions has an impact on the lattice parameters of the crystal structure Minorchange in Mn-O bond length and Mn-O-Mn bond angle in Mn3+–O–Mn4+ network [15, 16] produces large variation in the magnetic and transport properties of manganite perovskite Hence, the modification of Mn3+and Mn4+ ratio generates the change in electron carrier density of Mn–O–Mn network

perovskite with 0.050 ≤ x ≤ 0.100

The in-situ ultrasonic velocity/attenuation measurement is one of the exceptional and constructive methods for the comprehensive characterization of LSMMO manganite perovskites The interaction between ultrasonic waves and the coupling in manganite perovskites, results a change in lattice Any alteration occurring in the lattice degrees of freedom are reflected in the ultrasonic parameters like velocity and attenuation Hence,ultrasonic parameters discovers [17, 18] the FM-PM phase exchangeof any manganite perovskites

In this paper, solid state and sonochemical reaction methods are used to produce the

Mgdoped bulk and nanoLSMMO(0.050 ≤ x ≤ 0.100) manganite perovskite, respectively The

structural as well as the magnetic properties of LSMMO manganite perovskites are revealed employing different characterisation techniques Anorganized examination of bulk and nano LSMMO perovskites samples isdone by in-situ ultrasonic measurement

2 Experimental

2.1 Synthesis of La 0.7 Sr 0.3 Mg1-xMnxO 3manganites

The bulk and nano LSMMOmanganite perovskites with different values of x (0.050,

0.075 and 0.100) were formed by solid state [19] and sonochemical reaction process [20] Lanthanum nitrate (99.999%; Sigma-Aldrich, USA), strontium nitrate (99.9%; Sigma-Aldrich, USA), magnesium nitrate (99.0%; Himedia GR, India) and manganite carbonate (99.9%; Sigma-Aldrich, USA) were used to prepare the samples by stoichiometric ratio using similar

2.2 Density

The density of bulk and nanoLa 0.7 Sr 0.3 Mg 1-x Mn x O 3perovskite manganites was measured by liquid displacementmethod (Archimedes principle) with CCl4acts as buoyant The digital balance (Sartorius, Germany) was employed to evaluate the weight of prepared

perovskite manganitesin air (W a ) and in buoyant (W b) The density of the perovskite manganites [23]

X-nano La 0.7 Sr 0.3 Mg1-xMn x O 3 perovskite manganites are estimated with Rietveld’s and Scherrer’s equations [24, 25]

2.4 Microscopic studies

The morphology and topography of the prepared perovskite manganites was examined using Field Emission Scanning Electron Microscope (FE-SEM) coupled with X-rays Energy Dispersive Spectrum (EDX) (FEI Nova-Nano SEM-600, The Netherlands) The size of particles and its morphology were measured through Transmitting Electron Microscope (TEM,

b a

a W W

W

−

±

2.6 Ultrasonic velocities and attenuation

Transmission and reception of ultrasonic waves, by through transmission technique,in the manganite perovskites wasachieved usinghigh-power ultrasonic Pulsar Receiver (Olympus NDT, 5900 PR, USA) and high-frequency (1 GHz) Digital Storage Oscilloscope (Lecroy, Wave Runner 104 MXi, USA) The 5 MHz X-cut and Y-cut transducers were used to generate the longitudinal and shear ultrasonic waves (heating rate of 0.5 K min-1) The measurements were carried out [21, 22] with temperature from 300 to 400 Kusing the experimental set-up

designed in the author’s laboratory and the standard method [27] is employed to carry out the

error due to couplant correction

3 Results and discussion

3.1 Structural, elemental and surface area analysis

The X-ray diffraction image of the prepared LSMMO manganite perovskites is depicted in Fig 1.The image illustrates all samples are in single phase rhombohedral perovskite structure, agrees with the observed peak positions indexed for La0.70Sr0.30MnO3

(JCPDS 50-0308) [28, 29] Substituting Mg ion in the place of Mn maintains rhombohedral

structure and only a distortion in the MnO6octahedra is produced at Mn site The average crystallite sizes (DXRD) of the prepared LSMMO manganite perovskites are calculated from the full-width at half-maximum (FWHM) (β1/2) of the diffracted peaks using the Scherrer’s

directly proportional to the content of Mg in bulk and nano manganite perovskites

Lattice cell parameters (a, c) and unit cell volume are calculated (Table 1) to investigate the structural changes in the bulk and nano LSMMO manganite perovskites [31, 32] and found

that it varies with the content of Mg The obtained average Mn–O bond lengths (d Mn–O ) and Mn–O–Mn bond angles (θ Mn-O-Mn ) of LSMMO shows (Table 1) that there is a gradual

increase in average bond length while it decreases up to x = 0.10 of the average bond angle It

is interesting to note that an increase in Mn-O bond length in nano manganite perovskites leads

to an overlap between the closest orbits of Mn ions and the nearest O ions The DE interactions

in nano manganite perovskites between Mn3+ and Mn4+ ions via O2+ becomes weak than in the

corresponding bulk manganite perovskites [33] Thus, the subsequent bulk sample is higher

than that of the FM-PM phase transition temperature (TC) of nanoperovskites

The tolerance factor for the Mg doped La 0.7 Sr 0.3 MnO 3 Perovskite for different compositions (x = 0.05, 0.075 and 0.100) are obtained using the Goldschmid’s equation [34] The tolerance factor for the LSMMO perovskite is 0.8548, 0.8540, 0.8532 respectively for x = 0.05, 0.075 and 0.100 The values obtained for LSMMO perovskite manganite materials is almost same as the undoped La 0.7 Sr 0.3 MnO 3 (Tolerance factor = 0.8564)

EDX spectra of bulk and nano LSMMO manganite perovskites are shown in Fig 2 It

is obvious from the EDX spectra that these manganite perovskites are composed of La, Sr, Mn,

Mg, and O atoms The atomic ratio of the constituent elements derived from the EDX pattern is

The surface area values for the bulk LSMMO manganite perovskites are 2.75, 2.43, and 2.18 m2 g-1, respectively, for x = 0.050, x = 0.075, and x = 0.100, whereas those for nano

samples are 24.61, 22.96, and 21.44 m2 g-1, respectively, for x = 0.050, x = 0.075 and x =

0.100 With an increase in Mg content in bulk and nano manganite perovskites, a decrease in

the surface area is noticed The equivalent spherical diameter (DBET) of bulk and nano

LSMMO manganite perovskites is calculated using the formula

DBET =

BET S

ρ

6

(2)

whereρ is the density of the sample

It is observed from the lower surface area (Table 1) of bulk LSMMO manganite perovskites, the number of atoms at the surface of nano LSMMO manganite perovskites is more than that of the corresponding bulk sample and hence, large proportions of atoms will be either at or near the grain boundaries of the surface [35]

3.2 Microscopic studies

Figures 3–5 [i - vi] show SEM and TEM images of bulk and nano LSMMO manganite perovskites, respectively The spherical-like morphology with definite grain boundaries of manganite perovskite particles is observed from the SEM images SEM and TEM images (Table 1)demonstratean increase in the particle size of bulk and nanoLSMMO manganite

perovskites with an increase in Mg content from x = 0.050 to x = 0.100 and it is confirmed by

characterization studies The circular lines in Selected Area Electron Diffraction (SAED) of LSMMO manganite perovskites(Fig 4) are crystalline in nature

in the Mg content, the density of LSMMO decreases XRD analysis infers that with an increase

in the Mg content in manganite perovskites, the volume of the unit cell increases which leads

to lose packing of the manganite perovskites Hence, density decreases with an increase in Mg content [36]

3.3 Velocities and attenuations through ultrasonic studies

The temperature dependent ultrasonic velocity and attenuation values are used to reveal the phase transitions and its behavior during the aging of the manganite perovskites The ultrasonic velocity and attenuation along with the derived elastic constant values are presented

in Table 3 The ultrasonic velocity (longitudinal and shear)increases with increase of Mg content in a particular temperature The anomalous behavior in the temperature dependent

ultrasonic parameters confirms existence of phase transitions at T Cin manganite perovskites [37, 38] The temperature dependent longitudinal velocity (UL), shear velocity (US), longitudinal attenuation (αL) and shear attenuation (αS) are respectively shown in Figs 5-8 The non-linear variation in velocity/ attenuation is the consequence of structural or phase transition occurs in the perovskites [17, 18] The observed dip in velocity and a peak in attenuation in manganite perovskites are correlated with FM and PM transition temperature

The initial and finaltemperatures, exhibiting anomalous behaviors, of the bulk and nano LSMMO samples are presented in Table 4 The whole range of temperature (300–400 K) of each manganite perovskite is categorized into three regions, namely, Region I (from 300 K to the temperature at which anomalous behavior starts, i.e., 364 K for BLSMMO005, 361 K for BLSMMO075, 354 K for BLSMMO100, 350 K for NLSMMO005, 346 K for NLSMMO075

K, and 348 K for NLSMMO100)

With an increase in the temperature, thermal phonons are created in the lattice of the prepared samples, consequence a decrease in the velocity and increase in attenuation

However, a strong interaction between the structure, the spin, and the orbital exists at T C,

causing an equivalent strain in the lattice A change in ultrasonic velocity and attenuation with temperature is directly linked with the lattice degrees of freedom [39]

Apart from the anomalous region, the ultrasonic parameters show a regular behavior like that of aging of the solid material The velocity gradually decreases and attenuation increases with the increase in temperature takes place from 300–364 K (Region I) and from 371–400 K (Region III) in BLSMMO005 sample In the temperature region from 364–371 K, (Region II) the sample shows sudden reduction in velocity starts from 364 K and reaches a minimum at 368 K, followed by a sharp increase in velocity up to 371 K After a brief analysis,

it is confirmed [17, 37] that the temperature with minimum velocity at the anomalous region

(Region II) is the Curie temperature (T C) of the perovskite However, 368 K is the Curie temperature for BLSMMO050 manganite perovskite

Minimum velocity and maximum attenuation is observed in a temperature obeyed in the phase diagram of LSMO samples [40, 41] The temperature at the variation of ultrasonic velocity/attenuation is observed is in agreement with the temperature at which FM-PM phase transition occurs in manganite perovskites [31–33] Similarly for manganite perovskites BLSMMO075, BLSMMO100, NLSMMO050, NLSMMO075, and NLSMMO100 samples, anomalies in velocity and attenuation are observed at 361–367 K, 354–359 K, 350–363 K, 346–355 K, and 342–348 K, respectively Likewise, the Curie temperature for these manganite

The decrease of transition temperature with an increase in Mg content (from x = 0.050

to 0.100) in bulk and nano La 0.7 Sr 0.3 Mg1-xMn x O 3perovskite may be attributed to the appearance of Mg2+ ions in the lattice The additional involvement of super exchange interaction pairs of Mn4+- Mn4+, Mg2+- Mn4+, Mg2+-Mn3+, Mg2+- Mg2+.directs to strengthen the AFM phase [33] The increase in the Mg2+ content, additional Mn4+ ions are presented into the lattice and hence, the content of Mn3+ ions is reduced Consequently, deteriorate in DE

interaction disapproval the metallicity and ferromagnetism [37, 42] Further, T C for nano manganite perovskites is lower than that for the corresponding bulk perovskite samples [17,

18, 43]

The bulk LSMMO manganite perovskites shows(Figs 5–8) a sharp transition in FM, while nano perovskite samples displaya broad transition in FM This is in line with the observation made in the XRD pattern for nanocrystalline samples In order to elucidate the

observed behavior, Curie temperature (TC) and transition width (∆TC) of all samples are noted (Table 4) It is seen that the broadened transition observed in nano LPMO samples indicate a diffused FM phase transition, i.e., absence of sharp transition [44]

Decrease in velocity and increase in attenuation at T Ccan be compared to lattice softening [17, 37, 38] Generally, lattice softening is caused due to a decrease in velocity and

an increase in attenuation, while lattice hardening is caused due to an increase in velocity and a decrease in attenuation [37, 38] The transformation in the strong link existing between the

spin, the charge, the orbital and the lattice degrees of freedom, and the interactions at T Care responsible for the observed anomaly in ultrasonic velocity and attenuation

For better understanding the inconsistency in ultrasonic parameters, the transition width

of temperature and the transition height of UL are measured and given in Table 3 The transition width of BLSMMO005, BLSMMO075, and BLSMMO100 perovskites are 7, 6, and 5K in temperature (∆T) respectively and 13, 9, and 6K for NLSMMO005, NLSMMO075, and NLSMMO100 The DE interaction of Mn3+-Mn4+ions diminishes by decreasing the transition width of temperature with increase in Mg content [46] The decrease in the transition height and the existence of anomalies in both UL and US [38, 47] is the consequence of decrease in linear magnetostriction effect with increase in Mg content results As a result, the spin-phonon interactions decrease with the linear magnetostriction effect sequentially reduces the phase transition temperature TC [47] Thus, the linear magnetostriction effect is supported by the anomaly in the temperature dependent ultrasonic parameters, which are mainly due to spin-

phonon interactions in bulk and nano LSMMO samples at T C [17, 37]

Further, the increase in ultrasonic velocity and decrease in attenuation decreases acoustical activation energy (EP) The experimental dip and peak in the ultrasonic velocity and attenuation at TC are due to the decrease in EP and thermally activated structural relaxation along with the existence of a single relaxation process as per Arrhenius relation (τ = τ0exp (EP/kT)) [48] The decrease in acoustical energy EP with an increase in Mg content

in the manganite perovskite samples can be confirmed by the increase in ultrasonic velocity and decrease in attenuation

With the increase of Mg content in the manganite perovskites (Mn3+is reinstated by

Mg2+)resultsthe mobility of the charge carrier decreases as DE interaction is weakened and hence, resistivity increases [40,41] Thus, the increase in Mg content leads to the contestamong the lattice degrees of freedom, the orbital, the charge and the spin results a decrease in CMR and consequently the MI and FM transitions become feeble These results reveal the direct confirmation for coupling and interactions/competitions owing to the effect of doping of Mg in manganite perovskites

The larger fluctuations occurred in the lattice volume around the phase transition [37, 51] lead to the distinct inconsistency in the first derivative of the ultrasonic parameters (Fig 9)

It is ascribed to the significant reduction in JT distortion of Mn3+O6octrahedral is due to

spin-lattice interaction below T C Further, the pronounced deviation in the peak in velocity at 368,

364, 357, 356, 351, and 345 K respectively for BLSMMO050, BLSMMO075, BLSMMO100, NLSMMO050, NLSMMO075, and NLSMMO100 perovskites again confirm the phase transition temperature TC Diminishing DE interaction, reduction in CMR and decrease in TC

of the Mg doped manganite perovskitesare more suitable for the magnetic refrigeration applications

4 Conclusions

The bulk and nanostructured La 0.7 Sr 0.3 Mg1-xMn x O 3manganite perovskiteswith different Mg content (x=0.050, 0.075 and 0.100) are produced using solid-state reaction and sonochemical methods The crystallinity and phase purity of perovskites are determined by XRD studies with the lattice parameters, Mn-O bond length and Mn-O-Mn bond angle Particle size of bulk LSMMO (260–850 nm) and nanoLSMMO manganite perovskites(23 and

86 nm) are estimated by microscopic characterization studies and found it increases with increase in Mg content In-situ ultrasonic velocities and attenuation measurement shows the FM–PM transitions (TC) at temperatures 368, 364, and 357 K for bulk BLSMMO050,

2 J Fan, W Zhang, X Zhang , L Zhang, Y Zhang, Scaling analysis of PM–FM phase transition in Nd0.5Sr0.25Ca0.25MnO3 based on magnetic entropy change,Mater Chem

Phys 144 (2014), 206-211

3 Ch.-S Park, M-H Hong, S Shin, H.C Hyung, H.H Park, Synthesis of mesoporous

La0.7Sr0.3MnO3 thin films for thermoelectric materials, J Alloys Compd 632 (2015)

6 Y Zhong, P Chen, B Yang, X Zuo, L Zhou L, X Yang, G Li, Low-cost free counter electrode of La0.67Sr0.33MnO3 perovskite for efficient dye-sensitized solar

platinum-cells, Appl Phys Lett 106 (2015) 263903-263906

7 M.K Vaishnavi, B Dhananjay M.P Kishore, Lanthanum strontium manganite oxide (LSMO) nanoparticles: a versatile platform for anticancer therapy, RSC Adv 5(74) (2015) 60254

8 S Agrestini, N L Saini, A Bianconi Determination of local distortions in the charge ordered and CMR La1−xCaxMnO3 manganites, J Magn Magn Mater, 272–

276(1)(2004) 454-455

9 P K Siwach, H K Singh, O N Srivastava, Low field magnetotransport in

manganites, J Phys.: Condens Matter 20 (2008) 273201-273244

10.S Vikram, P Neeraj G L Bhalla, S K Agarwal, Structural, magnetotransport and morphological studies of Sb-doped La2/3Ba1/3MnO3 ceramic perovskites, J Phys

Chem Solids 68(9) (2007) 1685-1691

11.M Izumi, Y Murakami, Y Konishi, T Manako, M Kawasaki, Y Tokura, Structure characterization and magnetic properties of oxide superlattices La0.6Sr0.4MnO3/La0.6Sr0.4FeO3, Phys Rev B 60(2) (1999) 1211-1215

1-xSrxMnO3 for x≤0.2, J Phys.: Condens Matter 12(17) (2000) 3993-4011

13.A Mellergard, R L McGreevy, S.G Eriksson, Structural and magnetic disorder in LaxSrxMnO3, J Phys: Condens Matter 12(23) (2000) 4975-4991

1-14.L Despina, T Egami, Evidence of local lattice distortions in La1−xSrxMnO3 provided

by pulsed neutron diffraction, J Appl Phys.; 81 (1997) 5484-5486

15.C Thiele, K Dorr, O Bilani, J Rodel, L Schultz, Influence of strain on the magnetization and magnetoelectric effect in La0.7A0.3MnO3/PMN-PT(001) (A=Sr, Ca),

Phys Rev B 75 (2007) 054408-054415

16.T Shimura, T Hayashi, Y Inaguma, M Itoh, Magnetic and electrical properties of

LayAxMnwO3 (A= Na, K, Rb, and Sr) with perovskite-type structure, J Solid State

J Phys Chem Solids 74(2) (2013) 205-214

19.I.P Parkin, Solid state metathesis reaction for metal borides, silicides, pnictides and

chalcogenides: ionic or elemental pathways, Chem Soc Rev 25 (1996) 199-207

20.J A Schwarz, C Contescu, A Contescu, Methods for preparation of catalytic

materials, Chem Rev 95(3) (1995) 477-510

21.S Praveenkumar, K Sakthipandi, R Gayathiri, M Sridharpanday, A Karthik, V Rajendran, Ferromagnetic–paramagnetic transition temperature in bulk and nanostructured La0.7SrxCa0.3-xMnO3 (x = 0.10, 0.15, and 0.20) manganite materials Rare Metals 2015 http://link.springer.com/article/10.1007%2Fs12598-015-0516-3 Accessed 27 May 2015

22.K Sakthipandi, V Rajendran, Metal insulator transition of bulk and nanocrystalline

La1−xCaxMnO3perovskite manganite materials through in-situ ultrasonic measurements,

Mater Charact; 77 (2013) 70-80

23.S Sankarrajan, S Aravindan, R Yuvakumar, K Sakthipandi, V Rajendran, Anomalies

of ultrasonic velocities, attenuation and elastic moduli in Nd1− xSrxMnO3 perovskite

manganite materials, J Magn Magn Matt 321(21) (2009) 3611-3620

24.D B Wiles R A Young, A new computer-program for rietveld analysis of

X-ray-powder diffraction patterns, J Appl Cryst 14 (1981) 149-151

25.J F Bussiere, On-line measurement of the microstructure and mechanical properties of

steel Materials evaluation 44(5) (1986) 560-567

26.B R Jennings, K Parslow, Particle size measurement: the equivalent spherical

diameter, Proc R Soc Lond A 419(1856) (1988) 137-149

27.P Palanichamy, P Kalayanasundram, B Raj Couplant correction for ultrasonic