Ba0.5CaxSr0.5-xTiO3 (BCST) ceramics, where x= 0, 0.1, 0.2, 0.3 and 0.4, were prepared by
the conventional solid state reaction technique. X-ray diffraction (XRD)
analysis confirmed the formation of BST perovskite phase structure besides some
calcium oxide peaks for samples with high Ca content, x. Scanning electron
microscopy (SEM) results confirmed the XRD results, i.e., as x increased, the average grain size decreased. Energy
dispersive X-ray (EDX) analysis verified the increase of the amount of Ca
element with increasing of its content. Mechanical properties such as ultrasonic
attenuation, longitudinal wave velocity, and longitudinal elastic modulus were
studied by an ultrasonic pulse echo technique at 2 MHz frequency.
Investigations of ceramic microstructures and mechanical properties showed
their dependence on composition. Increasing of Ca content resulted in a
decrease in bulk density and ultrasonic attenuation and an increase in
porosity, velocity, and modulus. High temperature ultrasonic studies showed, in
addition to Curie phase transition, three or more relaxation peaks and its
origin was investigated.
L. C. Sengupta and S. Sengupta, “Novel Ferroelectric Materials for Phased Array Antennas,” IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 44, No. 4, 1997, pp. 792-797.
S. S. Gevorgian and E. L. Kollberg, “Do We Really Need Ferroelectrics in Paraelectric Phase Only in Electrically Controlled Microwave Devices?” IEEE Transactions on Microwave Theory and Techniques, Vol. 49, No. 11, 2001, pp. 2117-2124. doi:10.1109/22.963146
W. Chang and L. Sengupta, “MgO-mixed Ba0.6Sr0.4TiO3 Bulk Ceramics and Thin Films for Tunable Microwave Applications,” Journal of Applied Physics, Vol. 92, No. 7, 2002, pp. 3941-3946. doi:10.1063/1.1505669
M. Kuwabara, H. Matsuda and Y. Ohba, “Varistor Characteristics in PTCR-Type (Ba,Sr)TiO3 Ceramics Prepared by Single-Step Firing in Air,” Journal of Materials Science, Vol. 34, No. 11, 1999, pp. 2635-2639.
J. F. Scott, M. Azuma, E. Fujii, T. Otsuki, G. Kano, M. C. Scott, C. A. Paz de Araujo, L. D. McMillan and T. Roberts, “Microstructure-Induced Schottky Barrier Effects in Barium Strontium Titanate (BST) Thin Films for 16 and 64 Mbit (DRAM cells),” Proceedings of International Symposium on Integrated Ferroelectrics, New York, 1992, p. 356.
T. Hu, H. Jantunen, A. Uusimaki and S. J. Leppavuori, “BST Powder with Sol-Gel Process in Tape Casting and Firing,” Journal of the European Ceramic Society, Vol. 24, No. 6, 2004, pp. 1111-1116.
V. V. Lemanov, “Concentration Dependence of Phonon Mode Frequencies and the GrüNeisen Coefficients in BaxSr1-xTiO3 Solid Solutions,” Physics of the Solid State, Vol. 39, No. 2, 1997, pp. 318-322.
B. L. Cheng, M. Gabbay, M. Maglione and G. Fantozzi, “Relaxation Motion and Possible Memory of Domain Structures in Barium Titanate Ceramics Studied by Mechanical and Dielectric Losses,” Journal of Electroceramics, Vol. 10, No. 1, 2003, pp. 5-18.
A. Ioachim, M. I. Toacsan, M. G. Banciu, L. Nedelcu, C. Plapcianu, H. V. Alexandru, C. Berbecaru, D. Ghetu, G. Stoica and R. Ramer, “Frequency Agile BST Materials for Microwave Applications,” Journal of Optoelectronics and Advanced Materials, Vol. 5, No. 5, 2003, pp. 1389-1393.
M. H. Badr, L. M. Sharaf El-Deen, A. H. Khafagy and D. U. Nassar, “Structural and Mechanical Properties Characterization of Barium Strontium Titanate (BST) Ceramics,” Journal of Electroceramics, Vol. 27, No. 3-4, 2011, pp. 189-196. doi:10.1007/s10832-011-9664-5
O. P. Thakur, C. Prakash and D. K. Agrawal, “Dielectric Behavior of Ba0.95Sr0.05TiO3 Ceramics Sintered by Microwave,” Materials Science and Engineering: B, Vol. 96, No. 3, 2002, pp. 221-225.
C. Berbecaru, H. V. Alexandru, C. Porosnicu, A. Velea, , A. Ioachim, L.Nedelcu and M. Toacsan, “Ceramic Materials Ba(1-x)SrxTiO3 for Electronics—Synthesis and Characterization,” Thin Solid Films, Vol. 516, No. 22, 2008, pp. 8210-8214. doi:10.1016/j.tsf.2008.04.031
S. Yun, X. Wang, B. Li and D. Xu, “Dielectric Properties Ca-Substituted Barium Strontium Titanate Ferroelectric Ceramics,” Solid State Communications, Vol. 143, No. 10, 2007, pp. 461-465. doi:10.1016/j.ssc.2007.06.031
V. V. Lemanov, A. V. Sotnikov, E. P. Smirnova, P. P. Syrnikov and E. A. Tarakanov, “Phase Transitions and Glasslike Behavior in Sr(1-x)BaxTiO3,” Physical Review B, Vol. 54, No. 5, 1996, pp. 3151-3157.
A. K. Singh, Subrat K. Barik, R. N. P. Choudhary and P. K. Mahapatra, “Ac Conductivity and Relaxation Mechanism in Ba0.9Sr0.1TiO3,” Journal of Alloys and Compounds, Vol. 479, No. 1-2, 2009, pp. 39-42.
Y.-C. Liou and C.-T. Wu, “Synthesis and Diffused Phase Transition of Ba0.7Sr0.3TiO3 Ceramics by a Reaction-Sintering Process,” Ceramics International, Vol. 34, No. 3, 2008, pp. 517-522. doi:10.1016/j.ceramint.2006.11.005
C. Fu, C. Yang, H. Chen, W. Wang, and L. Hu, “Microstructure and Dielectric Properties of BaxSr1-xTiO3 Ceramics,” Materials Science and Engineering: B, Vol. 119, No. 2, 2005, pp. 185-188.
A. Ioachim, R. Ramer, M. I. Toacsan, M. G. Banciu, L. Nedelcu, C. A. Dutu, F. Vasiliu, H. V. Alexandru, C. Berbecaru, G. Stoica and P. Nita, “Effect of the Sintering Temperature on the Ba(Zn 1/3Ta 2/3)O3 Dielectric Properties,” Journal of the European Ceramic Society, Vol. 27, No. 2-3, 2007, pp. 1117-1122.
A. Ioachim, H. V. Alexandru, C. Berbecaru, S. Antohe, F. Stanculescu, M. G. Banciu, M. I. Toacsan, L. Nedelcu, D. Ghetu, A. Dutu and G. Stoica, “Dopant Influence on BST Ferroelectric Solid Solutions Family,” Materials Science and Engineering: C, Vol. 26, No. 5-7, 2006, pp. 1156-1161. doi:10.1016/j.msec.2005.09.045
H. Frayssignes, B. L. Cheng, G. Fantozzi and T. W. Button, “Phase Transformation in BST Ceramics Investigated by Internal Friction Measurements,” Journal of the European Ceramic Society, Vol. 25, No. 13, 2005, pp. 3203-3206. doi:10.1016/j.jeurceramsoc.2004.07.030
B. L. Cheng, B. Su, J. E. Holmes, T. W. Button, M. Gabbay and G. Fantozzi, “Dielectric and Mechanical Losses in (Ba,Sr)TiO3 Systems,” Journal of Electroceramics, Vol. 9, No. 1, 2002, pp. 17-23.