Ferroelectric aging

The discussion concerning the domination of the domain wall-clamping mechanisms in bulk ferroelectrics has been the subject of several reports [51-55, 65, 66, 73, 78] since the discovery of ferroelectric aging, and still remains an open question. Recently, it has been shown by calculations [77] that the clamping pressure exerted by oriented defect dipoles in a 1-D model is two to three orders of magnitude weaker than that exerted by the same amount of charges accumulated on grain boundaries. 

Zhang, L.X. and Ren, X. (2006) Aging behavior in single-domain Mn-doped BaTi03 crystals Implication for a unified microscopic explanation of ferroelectric aging. Phys. Rev., B73, 094121. 

Liu, W, Chen, L.Y., Zhang, L., Wang, Y, Zhou, C., Li, C., and Ren, X. (2006) Ferroelectric aging effect in hybrid-doped BaTi03 ceramics and the associated large recoverable electrostrain. Appl. Phys. Lett., 89, 172908. 

A further unusual characteristic of ferroelectric materials is that their properties change with time in the absence of either external mechanical or electrical stresses or temperature changes. This ageing is due to a diminution of domain wall mobility through the gradual build-up of inhibiting causes. These may be internal fields due to the alignment of dipoles formed from lattice defects... 

Electrostrictive materials offer important advantages over piezoelectric ceramics in actuator applications. They do not contain domains (of the usual ferroelectric type), and so return to their original dimensions immediately a field is reduced to zero, and they do not age. Figure 6.24(a) shows the strain-electric field characteristic for a PLZT (7/62/38) piezoelectric and Fig. 6.24(b) the absence of significant hysteresis in a PMN (0.9Pb(Mg1/3Nb2/303-0.1 PbTi03) electrostrictive ceramic. 

Figure 18.15 Application of the model of hardening-softening transitions to the case of an aged and quenched state of a ferroelectric system with alternating distribution of charged defects, (a) Domain wall free energy versus...

It is important to note that ceramic capacitors made with ferroelectric formulations display a decay of capacitance and dielectric loss with time. This phenomenon, called aging, is reversible and occurs due to the crystal structure and to its changes with temperature. 

Mulloni V, Mazzoleni C, Pavesi L (1999) Elaboration, characterization and aging effects of porous silicon microcavities formed on lightly //-type doped substrates. Semicond Sci Technol 14 1052 Murzina TV, Fedor Yu Sychev, Kolmychek I A, Aktsipetrov OA (2007) Tunable ferroelectric photonic ciystals based on porous silicon templates infiltrated by sodium nitrite. Appl Phys Lett 90 161120... 

Class 2 capacitors are based on ferroelectric materials with considerably higher dielectric constants such as those listed in Table 3.10. These materials exhibit shifts in dielectric constant as a function of time (aging). This phenomenon is a result of ferroelectric domain movement over time. A typical aging curve is shown in Fig. 3.27. The application of heat. 

The very existence of domains and their behavior under applied stress has considerable bearing on all those properties of ferroelectrics which have currently been found useful. These include optical properties important for the application to modulators and for the basic study of the ferroelectric mechanism on an atomic scale electrical properties important in applications as dielectric, resistance, parametric, or memory elements and mechanical properties in relation to piezoelectric transducers and as potential materials having special high-temperature strength characteristics. In all these applications the special limitations of high applied stress fields are important especially in relation to the properties of coercivity, loss, saturation, and aging, all of which are intimately related to domain nucleation and kinetics. 

In addition to the magnitude of the polarization and dielectric constant, other properties of importance which determine usefulness for a particular application are ease of polling, hysteresis losses, loop squareness, temperature and frequency dependence of the above ferroelectric properties, and aging effects. Aging refers to the stability of frequency as a function of time and is particularly important for filters. ... 

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