Aims: The initial process of electric poling and the conditions of electrical boundaries significantly affect the physical properties of lead-zirconate-titanate (PZT) piezoelectric ceramics. This chapter explores electrothermal coupling in piezoelectrics and ferroelectrics, considering both static and dynamic thermodynamics. It highlights thermal differences in unpoled and poled PZT along the poling direction under open- and short-circuit conditions. To develop high power-density piezoelectrics, it is essential to understand thermal diffusivity to grasp the temperature profile of a high-voltage-driven specimen. Essentially, high thermal diffusivity is crucial for high-power piezoelectric materials.
Methodology: By examining the transient temperature profile
at the "insulated side" of the disk sample, the thermal diffusivity
\(\alpha_T\) can directly be measured by finding the time constant T
experimentally from fitting the temperature profile
\(\theta_0[1-e^{-t/\tau}]\) at x = L.
Results: The "secondary electrothermal" coupling
factor \(k^\lambda\) is introduced, akin to the electromechanical coupling
factor k, to account for why thermal diffusivity is greater under short-circuit
conditions than open-circuit conditions. Conversely, the unpoled specimen shows
the lowest thermal diffusivity. In a uniform ferroelectric specimen with a
steady temperature distribution, equilibrium and dynamic phenomenology
determine heat capacitance and specific heat capacity. On the other hand,
spatially non-uniform (space-gradient) phenomenology leads to thermal
diffusivity and conductivity.
Conclusion: The article confirms that heat flow analysis
with an exponential trend over time, such as
\((1-\theta/\theta_s)=e^{-t/\tau}\), is an approximation rather than an exact
solution. The secondary electrothermal coupling factor \(k^\lambda\) is
introduced, which appears to be significantly larger than the primary
electrothermal coupling factor
\(k^{{ET}^2}=\frac{p^2}{(C^E_p/T)\varepsilon_0\varepsilon^X}\). Finally, the
dynamic heat generation profile in practical piezoelectric devices is analyzed
and discussed to aid in the development of high-power piezoelectric devices.
Author (s) Details
Kenji Uchino
Department of Electrical Engineering, The Pennsylvania State University,
University Park, PA 16802, USA.
Please see the book here:- https://doi.org/10.9734/bpi/crpps/v5/3176
