Emerging Lead Free Ferroelectric Materials-Potassium Bismuth Titanate & Sodium Bismuth Titanate | Chapter 3 | Innovations in Science and Technology: Shaping a Sustainable Future (Vol. 2)

 

With the advancement in technology, the environment and health are two most affected areas that need to be considered. Among all piezoelectric ceramics, Lead Zirconate Titanate is most widely used in almost all devices such as actuators, transducers, sensors, memory devices, switches, oscillators, etc. Lead being toxic should be replaced by some eco-friendly substitute. Bismuth Potassium Titanate (KBT) and Sodium Bismuth Titanate (NBT) are two emerging materials that can substitute PZT. Scientists are working on different methods of preparation, trying different dopants and substitutes in KBT and NBT to achieve the nearly same properties as PZT as high dielectric constant, large piezoelectric coefficient, high density, high breakdown strength, etc. Li, K, La, Sm, Dy, Ho, Nb, Mn, Fe, and Sb are some of the major dopants in NBT and KBT, which are recently been explored. Substitution of rare earth elements La, Sm, Ho and Dy in NBT resulted in an increase in grain size proportional to the radius of rare earth dopant. Further these ions also increase its temperature range for actuator applications. Particularly, Sm doping in NBT gives ultra-high storage density and efficiency. Li+ and K+ substitution in NBT increases its conductivity. Solid Solutions of barium titanate, strontium titanate and their derivatives with KBT & NBT exhibit unique properties. This chapter provides a brief outlook on the latest research on these two materials.

 

Author(s) Details

Poonam Pahuja
Department of Physics at G.G.D.S.D. College, Palwal, Haryana, India.

 

Jitender
Department of Physics at G.G.D.S.D. College, Palwal, Haryana, India.

Please see the book here:- https://doi.org/10.9734/bpi/mono/978-93-48006-49-3/CH3

Examining the Electrothermal Effects in Ferroelectric Materials | Chapter 7 | Current Research Progress in Physical Science Vol. 5

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