Influence of Gd+3 Cation Substitution on the Functional Properties of Al0.8La0.2TiO3 Nanoparticles

Influence of Gd+3 Cation Substitution on the Functional Properties of Al0.8La0.2TiO3 Nanoparticles

S Dastagiri1*, V. Ramesh Kumar2, K. E. Supriya1, M. V. Saritha1, M. Rajamohan Rao1 and M. V. Lakshmaiap**

1Department of Physics, Sri Krishnadevaraya University, Ananthapuramu, A.P, India-515003

2Department of Physics, Government Degree College, Atmakur, Kurnool, A.P, India-518003

Abstract:- In present, the work reports on the effect of Gd- substitution on Aluminum Lanthanum Titanate (ALT) perovskite structures, structural and optical properties. The Al0.8GdyLa0.2-yTiO3 (y= 0.01, 0.02, 0.03, 0.04) (AGLTO)

hydrothermally synthesized nanoparticles. The XRD indicates crystallite size, Micro-strain, dislocation density and FWHM (full-width half maxima). The Scherers formula and Williamson-Hall (W-H) analysis used the X-ray peak expansion technique to determine the crystalline sizes and lattice strain; it was observed that an inversely proportional relationship exists. Fourier transforms infrared spectra (FT- IR) tested the presence of Al-O, Gd-O, La-O & Ti-O based metal oxide (M-O) bonds at A & B sites. The Eg values are increased from 3.293 to 3.372 eV with increase of Gd content from y = 0.01 to 0.04 contents show the wide Eg values suggesting optoelectronic and sensor applications.

1. INTRODUCTION

   The perovskite titanates doped with rare earth components offered fascinating structural, morphological, electrical, dielectric, magnetic, magneto-caloric and piezoelectric, etc., properties [1]. Numerous researchers focused on different properties of notable perovskite titanates like MTiO3 (M = Ba, Ni, Mg, Sr, Pb, Al, La, Ca, Zn, Mn, Co, Eu, Zr and so forth,) [1]. Among these titanates, the aluminum titanates (AT) were concentrated in an exceptionally restricted way. Aluminum titanate perovskites were concentrated by past researchers [2-6] for primary, optical, photocatalytic, electrical and mechanical properties.

   Specifically, Sahu et al. [2], arranged the AT nanoparticles and detailed the tetragonal design and dielectric properties. Azarniya et al. [3], fostered the AT nanoparticles just as nanofibers. Further, the inside and out microstructure was explored. Bakhshandeh et al [4], detailed he photocatalytic action of AT nanoparticles. Ewais et al. [5], separated the AT based earthenware production from the aluminum sludge waste. Tang et al. [6], noticed the goliath electro rheological impacts in AT nanoparticles. From this review, unmistakably the writing on AT and its based nanomaterials was not accessible in a bountiful way. To expand the dielectric steady of Al0.8La0.2TiO3, we wanted to substitute the Gd-rare earth component. Consequently, the Al0.8GdyLa0.2-yTiO3 (y =

   0.01 – 0.04)/AGLTO nanoparticles were arranged through aqueous strategy, wherein a few benefits like low working temperatures, less force and tedious, great crystallinity,

   simple example planning, and modest were accomplished [7].

2. EXPERIMENTAL PART

   To set up the AGLTO nanoparticles, the trailblazer materials like La (NO3) 3.6H2O (99.8% temperance, Sigma-Aldrich), Al (NO3)3 9H2O (99.8% flawlessness, Sigma-Aldrich), Gd(NO3)3. 6H2 O (99.9% faultlessness, Sigma-Aldrich), and TiO2 (99.9% temperance, Sigma-Aldrich) were taken into another glass container containing refined water as per the stoichiometric extent. With the help of appealing stirrer, the forerunner mix was blended at a consistent blending speed of 420 rpm. After some time, the white and blended nitrate game plan was outlined. Finally, they got course of action was moved to another Teflon bowl of 300 ml limit. Thusly, the Teflon bowl containing the game plan was brought into the solidified steel autoclave. By then, to play out the watery reaction, the autoclave was kept inside the hot air oven for 8 h at 150ºC. Besides, the autoclave was chilled off to room temperature followed by the ejection of tests from the Teflon bowl. Accordingly, they got test was cleaned for a couple of times until the pH worth of the model shows up at 7. In addition, using the hot air grill, the model was dried for 120 min at 60º C. Fittingly, they got AGLTO nanoparticles gone through different depictions, for instance, X-ray diffractometer (XRD, Bruker, CuKa, k = 0.15406 nm), FT-IR spectrophotometer (IR inclination 1, Shimadzu) and UVApparent spectrophotometer (JASCO, V-670 PC) to ponder the underlying and optical properties, separately.

3. XRD ANALYSIS

   The X-ray diffraction patterns of AGLTO nanoparticles are recording as shown in Fig.1. These patterns provided multiple number of diffraction peaks indicating the polycrystalline nature. It is observed that the maximum intensity is recorded at two-theta angle 13.472o for all the samples. From the maximum intensity (Imax) data (see Table.1), its find that the intensity of the maximum peak position is increased from 6155 to 11840 with increase of Gd-content in the Al0.8La0.2TiO3 system. Therefore, it is confirmed that the substitution of Gd- element induced the crystallinity of Al0.8La0.2TiO3. However, its notice that these peak positions are not matched with any standard structure. Herein, the peak positions of x = 0.01 0.04 contents are identifying to be

   similar. Therefore, it indexed this unknown structure as X- structure. Furthermore, the average crystallite size (D) is

   Average Crystallite Size (D)

   Average Crystallite Size (D)

   Average Microstrain (

   Average Microstrain (

   evaluated using the Scherrer equation: D = 0.9/Cos, = wavelength of the CuK spectral line (0.15406 nm), =	60		D	0.0052
   full width half maxima (FWHM) and = angle of				0.0048
   diffraction [8]. The achieved data ensured that the D is note	50
   down to be altering from 23.2 to 41.5 nm for x = 0.01				0.0044
   0.04. The disorganized distinction trend is observed due to
   the unsystematic FWHM values. As the Gd+3 cations are				0.0040
   substituted into the Al0.8La0.2TiO3 system, the resultant X-	40
   structure will be contracted. The reason can be well				0.0036
   understood by Shannon ionic radii table [9]. According to this table, the ionic radii of cations are give as, Al+3: 0.039	30			0.0032
   nm, La+3: 1.22 Ã…, Gd+3: 1.053 Ã…, and Ti+4: 0.68 Ã…. In the
   AGLT resultant structure, the Gd+3 cations of small ionic radii can replace the La+3 cations of high ionic radii. Thus,	20			0.0028

   evaluated using the Scherrer equation: D = 0.9/Cos, = wavelength of the CuK spectral line (0.15406 nm), =	60		D	0.0052
   full width half maxima (FWHM) and = angle of				0.0048
   diffraction [8]. The achieved data ensured that the D is note	50
   down to be altering from 23.2 to 41.5 nm for x = 0.01				0.0044
   0.04. The disorganized distinction tend is observed due to
   the unsystematic FWHM values. As the Gd+3 cations are				0.0040
   substituted into the Al0.8La0.2TiO3 system, the resultant X-	40
   structure will be contracted. The reason can be well				0.0036
   understood by Shannon ionic radii table [9]. According to this table, the ionic radii of cations are give as, Al+3: 0.039	30			0.0032
   nm, La+3: 1.22 Ã…, Gd+3: 1.053 Ã…, and Ti+4: 0.68 Ã…. In the
   AGLT resultant structure, the Gd+3 cations of small ionic radii can replace the La+3 cations of high ionic radii. Thus,	20			0.0028

   the dimensions of the building block will be decreased. These result can be attributed to the significant homogeneity of the prepared AGLTO nanoparticles shown in Table.1; where dislocation density () shows the values between 5.806 x 1014 and 18.57 x 1014 m-2 respectively; an alternative form of the Gd contents is y = 0.01 to 0.04.This trend is attributed to the molecular weight of the sample is that raise from 145.412 to 145.963 g/mol as a content with "y".

   y = 0.04

   y = 0.03

   0.01 0.02 0.03 0.04

   Composition y

   Fig.2. Compositional dependence of D & of AGLTO nanoparticles

   Williamson – Hall (W – H) plot (Fig.3) is a known planning tool for estimating the average size of crystals (D) and fine deformation. W-H schemas are developed between Cos versus 4Sin of the current study using compatible linear relationships:

   40000

   Intensity (a.u)

   Intensity (a.u)

   30000

   20000

   10000

   0

   y = 0.02

   y = 0.01

   10 20 30 40 50 60 70 80

   2 (degree)

   Fig.1. XRD spectra of AGLTO nanoparticles

   Cos = 0.9 + 4sin (i .e. y = c + mx form),

   D

   Here, the slope of the straight line is related to microstrain

   ('), and the intercept value is related to the crystallite size (D'). The resulting values ' and D' are listed in Table 1. Finally, a good agreement is noticed between the values derived from the W – H plots based on Scherrer's theory and the values ' & D'. Based on the formula x = 0.01 to 0.02, D' increases and x = 0.03 -0.04 decreases D'. Micro- strain (') is decreases from x = 0.01 – 0.03 after x= 0.04 increase ' [11]. It can be seen in Fig.2, that there is an inverse proportional relationship between the two parameters D & [10]. In literature, similar types of results have been published. [9-12].

   Table: 1. Data on structural and physical parameters of AGLTO nanoparticles

   y	0.01	0.02	0.03	0.04
   D (nm)	23.2	41.5	38	37.9
   Imax	6155	9185	10421	11840
   M (g/mole)	145.412	145.596	145.779	145.963
   FWHM	0.9676
   () (radian)		0.4031	0.4437	0.4592
   0.00457		0.00337	0.00330	0.00478
   0.00124		0.00123	0.00107	0.00272
   D 26.4		45.6	38.4	38.3

   (m-2) 18.579 x 1014

   5.806 x

   1014

   6.925 x

   1014

   6.961 x

   1014

   Fig.3. W-H Plots of AGLTO nanoparticles

4. UV-VIS ANALYSIS

   In order to calculate the optical energy gap (Eg), the Kubelka-Munk function is consider. Using this, the function of reflectance F(R): (1-R)2/2R, (where R = reflectance which is recorded from diffuse reflectance spectra as shown in the inset of Fig.4 is computed [13]. Herein, the F(R) is observed to be directly proportional to the absorptivity () and therefore, in place of , its can substitute F(R). Further, using the equation: (h)n = m (h- Eg) and the (h)n versus photon energy (h) plots, it is calculating the Eg values of AGLT. The exponent (n) in the band gap equation is taken as 2 for direct transition of charge carriers between two energy bands [13]. The (h)n versus h plots of x = 0.01-0.04 contents showed the linear portions. These linear portions are extrapolated towards the h-axis. Then, using the intersecting position of the straight line at the h-axis, wherein approaches to zero, the Eg values are calculated. These Eg values are indexed in Fig.4. The results indicates that the Eg values are increased from

   3.293 to 3.372 eV with increase of Gd-content from x =

   0.01 to 0.04. This kind of behavior is mainly attributed to the oxygen vacancies present in the each composition. That

5. FT-IR ANALYSIS

   The Fourier transform infrared spectra (FTIR) spectra of AGLT nanoparticles are recorded over 4000 – 400 cm-1 wave number range and show in Fig.5. The A and B-site locations are indexed using the a and b. These two positions suggest indirectly the formation of perovskite structure. The a and b peaks are notice during the range of 590 to 613 cm-1 and 450 to 462 cm-1, respectively (see Table 3.). The formation of a and b absorption bands revealed the existence of the metal oxide (M-O: Al-O, La- O, Gd-O, Ti-O) stretching vibrations [8, 14]. Besides, the additional bands recorded at 720 to 736 cm-1 are also associated with the metal oxide bonds of parent perovskite. During 1057-1069 cm-1 and 3072-3617 cm-1 wave number range, the peaks are tailored owing to the O-H stretching and bending vibrations of H2O molecules absorbed by the AGLTO nanoparticles [8, 14]. This implied that all the contents are affected with moisture up to smaller extent.

   Table.3. Data on FTIR spectra of AGLTO nanoparticles

   y	A-site vibrational frequency a (cm-1)	B-site vibrational frequency b (cm-1)
   0.01	613.4	462.42
   0.02	581.8	460.66
   0.03	594.08	451.88
   0.04	590.57	460.66

   y	A-site vibrational frequency a (cm-1)	B-site vibrational frequency b (cm-1)
   0.01	613.4	462.42
   0.02	581.8	460.66
   0.03	594.08	451.88
   0.04	590.57	460.66

   is, the Eg value will be high for the less number of oxygen

   vacancy and vice versa [13]. In case of AGLT nanoflowers, the numbers of oxygen vacancy are decreased with increase f Gd-content. Therefore, the concerned distances between the valence and conduction bands are increased from 3.293 to 3.372 eV (see Table 2). However, the x = 0.01-0.04 contents show the wide Eg values suggesting optoelectronic and sensor applications [13].

   Table.2. Optical band gap (Eg

   ) of AGLTO nanoparticles

   120 0.01

   100

   120

   0.02

   100

   -1

   -1

   80

   3306.42 cm-1 3094 cm

   y	0.01	0.02	0.03	0.0.4
   Optical band gap (Eg) eV	3.293	3.303	3.338	3.372

   y	0.01	0.02	0.03	0.0.4
   Optical band gap (Eg) eV	3.293	3.303	3.338	3.372

   60 1069.42 cm-1

   Transmittance (% T)

   Transmittance (% T)

   40 736.28 cm-1

   a

   a

   = 613.4 cm-1

   20

   b

   b

   = 462.42 cm-1

   0

   80 3313.44 cm-1 -1

   3079.95 cm

   60

   40

   20

   0

   1066.33 cm-1

   732.77 cm-1

   a

   a

   = 581.8 cm-1

   b

   b

   = 460.66 cm-1

   4000 3500 3000 2500 2000 1500 1000 500

   120

   0.03

   100

   120

   100

   4000 3500 3000 2500 2000 1500 1000 500

   0.04

   80 3608.37 cm-1

   3072.93 cm-1

   80 3617.15 cm-1

   3079.95 cm-1

   3302.91 cm-1

   3306.42 cm-1

   60

   40

   20

   1069.84 cm-1 60

   725.75 cm-1 40

   a

   a

   = 594.08 cm-1 20

   1057.55 cm-1

   722.24 cm-1

   a

   a

   = 590.57 cm-1

   -1

   b

   b

   = 451.88 cm-1

   0

   4000 3500 3000 2500 2000 1500 1000 500

   = 460.66 cm

   b

   b

   0

   4000 3500 3000 2500 2000 1500 1000 500

   Wave number (cm-1)

   Fig.4. (h)2 versus h plots of AGLTO nanoparticles

   Fig.5. FTIR spectra of AGLTO nanoparticles

6. CONCLUSION

The AGLTO nanoparticles were prepared using the hydrothermal method. The XRD patterns of all samples indicated the highest peak at 13.472o. Also, the average crystallite size (D) was noted to be changing from 23.2 to

41.5 nm for AGLTO samples. The dislocation density () values are between 5.806 x 1014 and 18.57 x 1014 m-2 respectively; an alternative form of the Gd contents is y =

0.01 to 0.04. The W – H plots based on Scherrer's theory and the values ' & D' is a good agreement is. Furthermore, the optical band gap (Eg) was found to be increasing from

3.293 to 3.372 eV as a function of y. The formation of a and b absorption bands revealed the existence of the M-O stretching vibrations.

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