Rietveld Refinement of (Na0.5Bi0.5TiO3 )(Bi0.8 Ba0.2FeO3 ) Lead Free Ceramics
Kavita Kaswan*, Ashish Agarwal, Sujata Sanghi, Manisha Rangi
Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar-125001, Haryana,
India
*e-mail: kaswan.kavita@gmail.com; Tel.: +91-9416966795
Abstract
(1-x)(Na0.5Bi0.5TiO3)-x(Bi0.8Ba0.2FeO3) lead free ceramics
(NBT-BBFO; x=0, 0.1) were synthesized by conventional
solid state reaction method. Crystalline phase of sintered
ceramics was investigated at room temperature using X-ray
diffraction. Rietveld refinement of XRD data performed by
FullProf revealed that the prepared ceramics exhibit
rhombohedral structure with R3c space group.
Introduction
Lead based piezoelectric materials with perovskites
structure have variety of applications in sensors,
actuators, transducers and many other electronic devices
[1,2]. But due to high toxicity of lead oxide, the use of
the lead-based ceramics has caused serious lead
pollution and environmental problems. Therefore, it is
necessary to develop lead-free piezoelectric ceramics
for replacing them [3]. Sodium bismuth titanate is a
dielectric material which is being used widely due to its
high temperature dielectric constant and it is a lead free
material. In the present work Na0.5Bi0.5TiO3Bi0.8Ba0.2FeO3 (NBT-BBFO) ceramics have been
prepared by solid state reaction method.
Experimental
High purity Bi2O3, Na2CO3, TiO2, BaCO3, Fe2O3 (purity
˃ 99% Sigma-Aldrich) were used as starting materials.
The calcination of the above mixture was carried out at
an optimized temperature of 873 K for 5h and sintered
at 1173 K for 2h. After sintering, powder was reground
and subjected to powder XRD in the range 10-80̊ using
Rigaku Miniflex-II diffractometer with Cu Kα radiation
to confirm the phase formation and crystalline nature.
Results
Structural Analysis: Crystalline phase of sintered
ceramics was investigated at room temperature using Xray diffraction. Rietveld refinement of XRD data
performed by FullProf program represented that the
prepared ceramics exhibit rhombohedral structure with
R3c space group [1]. Low values of goodness of fit (χ 2)
for both samples suggested good fitting between the
experimental and simulated intensities as evidenced
from Fig.1.The lattice parameters and thus the volume
increased with the introduction of BBFO in the NBT
lattice. As we increase BBFO concentration in NBT
lattice, enhancement in stability is observed that is
evident by Tolerance factor. The value of tolerance
factor (t) calculated is equal to 0.9086 and 0.9131 for
NBT and NBT-BBFO respectively which indicates that
material belongs to stable perovskite structure[4].
Table 1. Refined structural parameters of
Na0.5Bi0.5TiO3 (NBT) ceramic
Atom
x
y
z
Profile fit
___________________________________________
Na/Bi 0.0
0.0
0.30883
Rp = 6.99
Ti
0.0
O
0.14433
0.0
0.03887
0.35101 0.17041
Rwp = 8.88
χ2 = 4.52
___________________________________________
NBT
Experimental
Simulated
Difference
Intensity a.u.
Keywords: Na0.5Bi0.5TiO3 ; Bi0.8Ba0.2FeO3 ; Rietveld
refinement ; Rhombohedral space group ; Structural
properties.
10
30
50
70
2θ (degree)
Fig 1. The experimental, simulated, and difference
curves from Rietveld refinement of Na0.5Bi0.5TiO
Acknowledgment
The authors are thankful to UGC for providing financial
support.
References
[1]S. Mahboob, G. Prasad, and G. S. Kumar, J. Mater.
Sci. 42 (2007)10275
[2]A. Hussain, C. W. Ahn, H. J. Lee, I. W. Kim, J. S.
Lee, S. J. Jeong, and S. K. Rout, Curr. Appl. Phys. 10
(2010) 305
[3]B. K. Barick, R. N. P. Choudhary, and D. K.
Pradhan, Mater. Chem. and Phys. 132 (2012) 1007.
[4] K. S. Rao, B. Tilak, K. C. V. Rajulu, A. Swathi,
and H. Workineh, Journal of Alloys and Compound,
509 (2011) 7121.