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

Abstract

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, P s ∼ 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.

Local piezo-response for lead-free Ba0.9Ca0.1Ti0.9Zr0.1O3 electro-ceramic by switching spectroscopy

“…This information suggests a little distortion of the Titanium cation position with respect to the position of the Oxygen cation 28 , with a degree of tetragonality c/a = 1.0025. This value is in agreement with the tetragonal distortion reported by V. S. Puli et al 29 . Consequently, it is necessary to take another approach to confirm the phase identification.…”

Synthesis and characterization of lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramic

“…Nevertheless, the maximum value of the dielectric loss remains <0. 32. Figure 4 displays polarization versus electric field (P-E) loops of the BCZT sample acquired at room temperature in the electric field ranging from 0.4 to 2.4 kV/cm.…”

“…31 Puli et al ceramics. 32 Li et al examined temperature stability of the piezoelectric properties of yttrium doped BCT-BZT system. 33 Similarly, effect of sintering aids and site substitution, especially on the piezoelectric properties, have been carried out in the parent BCZT system recently.…”

Revised structural phase diagram of (Ba0.7Ca0.3TiO3)-(BaZr0.2Ti0.8O3)

“…As a consequence, there is an increasing interest in the development of lead-free piezoelectric materials [8][9][10][11][12][13] with the main challenge to develop materials with an equivalent or even -on both ceramics and thin film samples (e.g. [15][16][17][18][19][20] ). The first structural phase diagram of BCTZ has been reported 14 and the different phase sequences with increasing temperature can be summarized as follows: (i) x ≤ 0.32: a single phase transition is observed from the low temperature R-phase to the high-temperature prototype cubic ̅ structure (C), (ii) 0.32 < x < 0.8 : presence of two phase transitions through a R-T-C phase sequence and (iii) x > 0.8: a single phase transition from a T-phase to the C-phase.…”