Structure and dielectric properties of yttrium-doped Ca0.28Ba0.72Nb2O6 ceramics

An unfilled tungsten bronze-structured ferroelectric ceramic, Ca0.28Ba0.72Nb2O6 (CBN28), has been doped with Y3+ to produce ceramics with a nominal composition, (Ca0.28Ba0.72)1-3w/2YwNb2O6 [0 <= w <= 0.05]. The substitution of Y3+ for Ca2+/Ba2+, and consequent additional vacancy formation, is assumed to occur on the A1/A2 sites. This resulted in a minor reduction of the c lattice parameter, and unit cell volume. For undoped CBN28, there was a slightly diffuse relative permittivity-temperature (epsilon r-T) peak at 268 degrees C. The peak became much broader for sample compositions w = 0.04 and 0.05 and the peak temperature showed a level of frequency dependence consistent with weak relaxor behaviour. The polarisation-electric field loops became narrower for samples w = 0.04 and 0.05, corresponding to a reduction in remnant polarisation value, from 2.4 to 0.8 mu C cm-2 (30 kV cm-1). The Y doped ceramics exhibited stable relative permittivity over a wide temperature range, the variation being within +/- 15% of the median value from 36 degrees C to 218 degrees C for w = 0.05, when measured at 1 kHz. Consequently, we suggest that A site donor-doping and aliovalent B site doping of CBN holds potential for industry standard, temperature stable, high temperature dielectrics (er >= 500 +/- 15% from - 55-250 + degrees C).(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Automated summary

An unfilled tungsten bronze-structured ferroelectric ceramic, Ca0.28Ba0.72Nb2O6 (CBN28), was doped with Y3+ to create ceramics with various compositions (Ca0.28Ba0.72)1-3w/2YwNb2O6 [0 <= w <= 0.05]. The substitution of Y3+ for Ca2+/Ba2+ resulted in a minor reduction of the lattice parameter and unit cell volume. Doped ceramics showed changes in permittivity, polarization, and temperature stability, indicating potential for high temperature dielectrics.