Porosity‐dependent properties of Nb‐doped Pb(Zr,Ti)O₃ ceramics

Abstract

In the present work, it is shown how the controlled porosity can be exploited to obtain a compromise between a reduced permittivity down to a few hundreds and maintaining a high tunability level as in the dense material, to fulfill requirements for tunable applications. Nb‐doped Pb(Zr,Ti)O3 ceramics with porosity in the range 5%‐30% have been prepared by direct sintering method. X‐ray diffraction analysis and Rietveld refinement indicated a co‐existence of tetragonal and monoclinic phases in the porous ceramics. Dielectric properties revealed a gradual reduction in permittivity when increasing the porosity level, while maintaining low dielectric losses below 3%. The ferroelectric switching behavior is also influenced by the porosity level: a continuous reduction in the saturation and remnant polarization is observed with increasing porosity. The nonlinear dielectric properties of all the investigated ceramics preserve a high level of tunability in comparison with one of the dense material, irrespective of the porosity level, while zero field permittivity was decreased below 1000. An optimum behavior is found for the ceramic sample with 25% porosity, which shows a high tunability, smaller losses, and moderate dielectric constant (ε ~600).

Effect of Porosity on Functional Properties of Lead-Free Piezoelectric BaZr0.15Ti0.85O3 Porous Ceramics

“…This behaviour may be assigned to Maxwell-Wagner relaxation due to charge inhomogeneities present inside the ceramic volume (air pore-ceramic interfaces, etc.). Similar behaviour was observed in other porous ceramics and was also assigned to interfacial polarisation [9,20,28]. All the samples show smaller losses for high frequencies (>1 kHz).…”

Understanding the effect of porosity on the polarisation-field response of ferroelectric materials

“…Pr with increasing porosity has been observed elsewhere [2,10,12,32,36] and it can been seen in Figure 2(B) that the experimentally measured Pr decreases at a faster rate compared to the volume rule of mixtures given by Eqn. 1, similar to that observed by Nagata [31] and Gheorghiu [12]. This indicates that the reduction in the fraction of ceramic is not the only reason for the decreased Pr and there is an additional depolarisation factor due to the presence of pores, which will be discussed in more detail in relation to the modelling results described later.…”

“…As a result, a thorough understanding of the influence of porosity on the properties of ferroelectric materials remains an important topic. To date, porosity in ferroelectric and piezoelectric materials has been considered at the micro-scale [7] and nano-scale levels [8], including bulk materials [9][10][11][12], textured materials [13], aerogels [14] and thin films [8,15].…”

“…An understanding of this topic is important since the level of polarisation will ultimately affect the final piezoelectric and pyroelectric properties of any porous ferroelectric. Work to date on understanding the polarisation-field response of porous ferroelectrics has considered modelling [23,30] and experimental approaches [8-10, 15, 31-34], along with combinations thereof [2,7,11,12,24,25,27,28,35], which will now be discussed in detail.…”

Investigation of Electromechanical Properties on 3-D Printed Piezoelectric Composite Scaffold Structures

“…Generally, in a dense ferroelectric sample, the electric field distribution is more or less homogenous and the dipoles could be aligned correspondingly [32]. However, by introducing low permittivity pores into the sample, the applied electric field tends to concentrate around the pores and thereby an inhomogenous electrical field distribution throughout the structure occurs [33].…”