Grain-size effects on properties of some ferroelectric ceramics

Abstract

Hot-pressed ceramics of the lead titanate zirconate system with different grain sizes were prepared and some of their electrical properties measured. The values of the dielectric and piezoelectric properties were analysed together with information on barium titanate ceramics already published in the literature. Many similarities were found between both systems. There are two main contributions to the properties : the single-crystal single-domain intrinsic effect and the contribution of the wall motion. These two effects are active at different values of grain sizes and the 90" wall thickness, compared with the grain size, is the 'key' to study their influence.The intrinsic effect is analysed considering the grains as monodomains. A model is developed which proposes that each grain has a different transition temperature r.. The r.values are taken as following a Gaussian distribution and the behaviour of the dielectric constant against temperature is computed and checked with experimental results. Measurements show that when the grain size decreases, r. increases, the maximum of the dielectric constant decreases, the peak widens and room temperature values of the dielectric constant become lower. All these results can be explained qualitatively with our model : a connection between findings and the idea of diffuse phase transitions is outlined.

Enhanced Dielectric and Ferroelectric Properties of Donor (W6+, Eu3+) Substituted SBT Ferroelectric Ceramics

“…The substitution of W 6+ for Ta 5+ in SBT results in the formation of cation vacancies which effectively reduces the concentration of oxygen vacancies which in turn significantly reduce the dielectric loss. Reduction in loss have been reported in other donor doped BLSFs also [25,49]. Fig.…”

“…This decrease in conductivity upon donor substitution improves the poling efficiency and thus higher d 33 values are obtained. It has also been reported that the incorporation of higher valent ions accompanied with cation vacancies at the A site in BLSFs, improves not only the ferroelectric property but also the piezoelectric one [49,125]. The piezoelectric constants have also been found to increase with increase in grain size [49].…”

“…On comparing the variation of in-plane lattice parameters a and b (Table 1) with tungsten concentration, we observe that with increasing tungsten concentration a decrease in the lattice parameters a and b is observed. It is this enhancement of ferroelectric structural distortion along with the introduction of cation vacancies at the A-site that lead to an eventual increase in T c value [21,25,47,[49][50]. In Fig.…”

Microstructure and texture dependence of the dielectric anomalies and dc conductivity of Bi3TiNbO9 ferroelectric ceramics

“…A diffuse phase transition is produced due to an inhomogeneous tension distribution originated by a reduced grain area. 25 It varies slightly the temperature of the maximum of permittivity from one grain to another. The observed anomaly at the transition would be the convolution of the different transition anomalies.…”

Influence of internal electric and elastic fields on characteristics of heterogeneous ferroelectric materials

“…[5][6][7][8][9][10][11][12] This dependence demonstrates an increase [13][14][15][16] as well as a decrease 17,18 of dielectric constant with decreasing the grain size.…”