arXiv subjects

Akshayveer

Publications and source records attributed to Akshayveer.

3 recordsLinked to original sources

arXiv2024

Phase-field thermo-electromechanical modelling of lead-free BNT-based piezoelectric materials

In recent yerars, Bismuth sodium titanate (BNT) and BNT-based piezoelectric materials have proved potential for lead-free piezoelectric technologies. Such materials' complicated phase structure is crucial to their thermo-electromechanical behaviour. Pure BNT has a rhombohedral (R3c) lattice structure at room temperature. The phase transition to an orthorhombic phase (Pnma) at 200\textcelsius is mainly due to octahedral tilting. This transition is called the depolarization temperature ($T_{d}$). The R3c phase ferroelectric domains have a higher spontaneous polarization, which declines with increasing temperature and reaches a local minimum at $T_{d}$, causing a phase change. Additionally, BNT transitions from Pnma to P4bm at 320\textcelsius and from P4bm to Pm3m at 520\textcelsius. These transitions also result in the changes in the spontaneous polarization. Therefore, the investigation of domain switching and phase change dynamics in relation to temperature and electromechanical coupling has acquired considerable importance. The complex phase regimes and their activation under different temperature settings will be examined to improve the use of these materials in sensors, actuators, energy harvesting devices, and haptic technologies. The micro-sized BNT inclusions are implanted in polydimethylsiloxane (PDMS) to reperesent the practical scenario. A two-dimensional phase-field thermo-electromechanical computational model has been created to investigate the complex phase transition and domain switching behaviour of BNT-PDMS composite under varying temperature conditions. The model uses Landau-Ginzburg and thermo-electromechanical free energy to accurately simulate phase shift and domain switching. Data from pure BNT experiments validated the model. It can predict thermo-electromechanical response in different phase regimes and temperature-induced phase coexistence.

cond-mat.mtrl-sci↗

arXiv2024

Piezoelectricity and flexoelectricity in biological cells: The role of cell structure and organelles

Living tissues experience various external forces on cells, influencing their behaviour, physiology, shape, gene expression, and destiny through interactions with their environment. Despite much research done in this area, challenges remain in our better understanding of the behaviour of the cell in response to external stimuli, including the arrangement, quantity, and shape of organelles within the cell. This study explores the electromechanical behaviour of biological cells, including organelles like microtubules, mitochondria, nuclei, and cell membranes. Two distinct cell structures have been developed to explore the cell responses to mechanical displacement, resembling actual cell shapes. The finite element method has been utilized to integrate the linear piezoelectric and non-local flexoelectric effects accurately. It is found that the longitudinal stress is absent and only the transverse stress plays a crucial role when the mechanical load is imposed on the top side of the cell through compressive displacement. The impact of flexoelectricity is elucidated by introducing a new parameter called the maximum electric potential ratio ($V_{\text{R,max}}$). It has been found that $V_{\text{R,max}}$ depends upon the orientation angle and shape of the microtubules. Further, the study reveals that the number of microtubules significantly impacts effective elastic and piezoelectric coefficients, affecting cell behaviour based on structure, microtubule orientation, and mechanical stress direction. The insight obtained from the current study can assist in advancements in medical therapies such as tissue engineering and regenerative medicine.

q-bio.QM↗

arXiv2023

The influence of thermo-electromechanical coupling on the performance of lead-free BNT-type piezoelectric materials

In recent times, there have been notable advancements in haptic technology, particularly in screens found on mobile phones, laptops, LED screens, and control panels. However, it is essential to note that the progress in high-temperature haptic applications is still in the developmental phase. Due to its complex phase and domain structures, lead-free piezoelectric materials such as BNT-based haptic technology behave differently at high temperatures than ambient conditions. Therefore, it is essential to investigate the aspects of thermal management and thermal stability, as temperature plays a vital role in the phase and domain transition of BNT material. A two-dimensional thermo-electromechanical model has been proposed in this study to analyze the thermal stability of BNT material by analyzing the impact of temperature on effective electromechanical properties and mechanical and electric field parameters. However, the thermo-electromechanical modelling of BNT ceramics examines the macroscopic effects of the applied thermal field on mechanical and electric field parameters as phase change and microdomain dynamics are not considered in this model. This study analyzes the impact of thermo-electromechanical coupling on the performance of BNT-type piezoelectric materials compared to conventional electromechanical coupling. The results predicted a significant improvement in piezoelectric response compared to electromechanical coupling due to increased thermoelectric effect in absence of phase change and microdomain switching for temperature boundary conditions below depolarization temperature ($T_{d}$~200$^{\circ}$C for pure BNT material).

cond-mat.mtrl-sci↗