Effects of La Doping on the Structural and Dielectric Properties of Barium Titanate Ceramics

Abstract:

Polycrystalline samples of Ba_1-xLa_xTiO₃ (x = 0.0, 0.002, 0.004) were prepared by a standard high-temperature solid-state reaction method. XRD studies confirmed the formation of a polycrystalline compound with a tetragonal crystal structure. SEM images suggested the presence of a polycrystalline microstructure with certain degree of porosity, and the grains appeared to be distributed inhomogeneously throughout the pallet samples. Dielectric studies indicated a ferroelectric–paraelectric phase transition with a clear shift in the Curie temperature (T_c) of BaTiO₃ towards a lower temperature upon doping. The brick-layer model was used to study the potential barrier and the structure of the grain-boundary region of the Ba_9.998La_0.002TiO₃ and Ba_9.996La_0.004TiO₃ ceramics. These ceramics exhibited good density and a homogeneous distribution of the grains. The thickness of the grain-boundary region was calculated to be approximately 200 nm.

• Periodical: Advanced Materials Research (Volume 975)
• Pages: 36-41
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.975.36
• Online since: July 2014
• Authors: Marcelo S. Silva*, Nilson S. Ferreira
• Keywords: Barium Titanate (BT), Crystal Structure, Dielectric Constant, Lanthanum Doping

References

[1] L.B. Ben, D.C. Sinclair, Anomalous Curie temperature behavior of A-site Gd-doped BaTiO3 ceramics: The influence of strain, Appl Phys Lett, 98 (2011).

DOI: 10.1063/1.3563710

[2] J. Rodriguez-Carvajal, FullProf: A Rietveld refinement and pattern matching analysis program (Version: October 2013), in, Laboratoire Léon Brillouin (CEA-CNRS), France, (2013).

[3] B.D. Cullity, S.R. Stock, Elements of X-Ray Diffraction, 3rd ed., Prentice-Hall, New Jersey, (2001).

[4] D.X. Yan, Z.P. Xu, X.L. Chen, D.Q. Xiao, P. Yu, J.G. Zhu, Microstructure and electrical properties of Mn/Y codoped Ba0. 67Sr0. 33TiO3 ceramics, Ceram Int, 38 (2012) 2785-2791.

DOI: 10.1016/j.ceramint.2011.11.049

[5] E. Brzozowski, M.S. Castro, C.R. Foschini, B. Stojanovic, Secondary phases in Nb-doped BaTiO3 ceramics, Ceram Int, 28 (2002) 773-777.

DOI: 10.1016/s0272-8842(02)00042-1

[6] Y. Luo, X.Y. Liu, X.Q. Li, J. Cheng, PTCR behaviour of Ba2LaBiO6-doped BaTiO3 ceramics, J Alloy Compd, 452 (2008) 397-400.

DOI: 10.1016/j.jallcom.2006.11.011

[7] N.J. Kidner, Z.J. Homrighaus, B.J. Ingram, T.O. Mason, E.J. Garboczi, Impedance/dielectric spectroscopy of electroceramics - Part 1: Evaluation of composite models for polycrystalline ceramics, J Electroceram, 14 (2005) 283-291.

DOI: 10.1007/s10832-005-0969-0

[8] J. Fleig, J. Maier, The impedance of ceramics with highly resistive grain boundaries: Validity and limits of the brick layer model, J Eur Ceram Soc, 19 (1999) 693-696.

DOI: 10.1016/s0955-2219(98)00298-2

[9] N.J. Kidner, B.J. Ingram, Z.J. Homrighaus, T.O. Mason, E.J. Garboczi, Impedance/dielectric spectroscopy of electroceramics in the nanograin regime, Mater Res Soc Symp P, 756 (2003) 39-50.

DOI: 10.1557/proc-756-ee4.6

[10] E. Brzozowski, M.S. Castro, Conduction mechanism of barium titanate ceramics, Ceram Int, 26 (2000) 265-269.

DOI: 10.1016/s0272-8842(99)00052-8

[11] S.M. Gheno, H.L. Hasegawa, P.I. Paulin, Direct observation of potential barrier behavior in yttrium-barium titanate observed by electrostactic force microscopy, Scripta Mater, 56 (2007) 545-548.

DOI: 10.1016/j.scriptamat.2006.10.033

[12] K. Hayashi, T. Yamamoto, Y. Ikuhara, T. Sakuma, Formation of potential barrier related to grain-boundary character in semiconducting barium titanate, J Am Ceram Soc, 83 (2000) 2684-2688.

DOI: 10.1111/j.1151-2916.2000.tb01616.x

[13] B.Y. Li, D.X. Zhou, D.L. Zhang, S.L. Jiang, Analysis on the aging characteristics of PTCR of donor-doped barium titanate, Mat Sci Eng B-Solid, 99 (2003) 394-398.

DOI: 10.1016/s0921-5107(02)00509-3

[14] M. Ramajo, E. Brozozowski, M.S. Castro, Estudio del perfil de defectos y de las propiedades eléctricas de BaTiO3 dopado con Nb y La, 41 (2002) 31-35.

DOI: 10.3989/cyv.2002.v41.i1.693

[15] M.M.V. Petrovic, J.D. Bobic, T. Ramoska, J. Banys, B.D. Stojanovic, Electrical properties of lanthanum doped barium titanate ceramics, Mater Charact, 62 (2011) 1000-1006.

DOI: 10.1016/j.matchar.2011.07.013