Colossal Permittivity in Microwave‐Sintered Barium Titanate and Effect of Annealing on Dielectric Properties

Colossal permittivity (e′ = 301,484 at room temperature and 1 kHz) of barium titanate was induced in ceramics synthesized using the microwave sintering method. Three different sintering processes (conventional, spark plasma, and microwave) were performed to better understand colossal permittivity in sintered barium titanate. The dielectric permittivity measurements revealed that the appearance of colossal permittivity has strong dependence on the sintering temperature and atmosphere, and less on the grain size of the sintered ceramics. However, the as-sintered barium titanate samples produced by microwave sintering show high dielectric loss (tanδ > 1) consistent with oxygen reduction during the microwave sintering process and consequent accumulation of oxygen vacancies and associated charge carriers at the grain boundary. Since the highly conductive state of as-sintered ceramics precludes their use in dielectric applications, thermal annealing at different conditions was performed to recover insulating characteristics. Microwave-sintered barium titanate with post annealing process (950°C for 12 h in air) showed low dielectric loss (tanδ = 0.045) at room temperature and 1 kHz, while still showing a much higher permittivity (e′ = 36,055) than conventionally sintered barium titanate (e′ = 3500).

[1]  Won Woo Cho,et al.  Paraelectric ceramics/metal dual composites SrTiO3∕Pt system with giant relative permittivity , 2006 .

[2]  M. Kosec,et al.  Colossal dielectric response in all-ceramic percolative composite 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3-Pb2Ru2O6.5 , 2009 .

[3]  Sintering of PZT powders in MW furnace at 2·45 GHz , 1999 .

[4]  Derek C. Sinclair,et al.  Giant Barrier Layer Capacitance Effects in CaCu3Ti4O12 Ceramics , 2002 .

[5]  Derek C. Sinclair,et al.  Characterization of Lanthanum-Doped Barium Titanate Ceramics Using Impedance Spectroscopy , 2001 .

[6]  Thierry Lebey,et al.  Colossal Permittivity in Ultrafine Grain Size BaTiO3–x and Ba0.95La0.05TiO3–x Materials , 2008 .

[7]  Arthur W. Sleight,et al.  High Dielectric Constant in ACu3Ti4O12 and ACu3Ti3FeO12 Phases , 2000 .

[8]  H. Abrams.  Grain size measurement by the intercept method , 1971 .

[9]  Shepard Roberts,et al.  Dielectric and Piezoelectric Properties of Barium Titanate , 1947 .

[10]  H. Verweij,et al.  Enhancement of dielectric and ferroelectric properties by addition of Pt particles to a lead zirconate titanate matrix , 2000 .

[11]  J D Katz.  Microwave Sintering of Ceramics , 1992 .

[12]  D. Lu,et al.  High‐Permittivity Double Rare‐Earth‐Doped Barium Titanate Ceramics with Diffuse Phase Transition , 2006 .

[13]  A. Hippel.  Ferroelectricity, Domain Structure, and Phase Transitions of Barium Titanate , 1950 .

[14]  Vijay K. Varadan,et al.  Dielectric and piezoelectric properties of microwave sintered PZT , 2001 .

[15]  D. Clark,et al.  Microwave Processing of Materials , 1996 .

[16]  Kyoichi Kinoshita,et al.  Grain‐size effects on dielectric properties in barium titanate ceramics , 1976 .

[17]  Shaikh,et al.  Dielectric properties of ultrafine grained BaTiO/sub 3/ , 1989, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[18]  D. M. Smyth,et al.  Defect Chemistry of Donor‐Doped BaTiO3 , 2006 .

[19]  X. Chen,et al.  Spark Plasma Sintering of Barium Zirconate Titanate/Carbon Nanotube Composites with Colossal Dielectric Constant and Low Dielectric Loss , 2011 .

[20]  W. Heywang,et al.  Semiconducting barium titanate , 1971 .

[21]  Fátima Esteban-Betegón,et al.  New Percolative BaTiO3–Ni Composites with a High and Frequency-Independent Dielectric Constant (εr ≈ 80000) , 2001 .

[22]  J. Binner,et al.  Bulk YBCO high- superconductors with uniform and full oxygen content via microwave processing , 1998 .

[23]  T. Lebey,et al.  Colossal dielectric permittivity of BaTiO3-based nanocrystalline ceramics sintered by spark plasma sintering , 2009 .