Barium zirconate-titanate/barium calcium-titanate ceramics via sol–gel process: novel high-energy-density capacitors

By Venkata Sreenivas Puli, Ashok Kumar, D. Chrisey, M. Tomozawa, J. Scott, R. Katiyar. Journal of Physics D: Applied Physics, 2011

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Lead-free barium zirconate-titanate/barium calcium-titanate, [(BaZr0.2Ti0.80)O3]1−x–[(Ba0.70Ca0.30)TiO3]x (x = 0.10, 0.15, 0.20) (BZT–BCT) ceramics with high dielectric constant, low dielectric loss and moderate electric breakdown field were prepared by the sol–gel synthesis technique. X-ray diffraction patterns revealed tetragonal crystal structure and this was further confirmed by Raman spectra. Well-behaved ferroelectric hysteresis loops and moderate polarizations (spontaneous polarization, Ps ∼ 3–6 µC cm−2) were obtained in these BZT–BCT ceramics. Frequency-dependent dielectric spectra confirmed that ferroelectric diffuse phase transition (DPT) exists near room temperature. Scanning electron microscope images revealed monolithic grain growth in samples sintered at 1280 °C. 1000/ε versus (T) plots revealed ferroelectric DPT behaviour with estimated γ values of ∼1.52, 1.51 and 1.88, respectively, for the studied BZT–BCT compositions. All three compositions showed packing-limited breakdown fields of ∼47–73 kV cm−1 with an energy density of 0.05–0.6 J cm−3 for thick ceramics (>1 mm). Therefore these compositions might be useful in Y5V-type capacitor applications.

Subfields: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Materials Chemistry

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