Our research focuses on the discovery, synthesis and characterization of adaptive smart materials that can be used to achieve energy sustainability, low-cost automated manufacturing and advanced healthcare solutions. Examples of such materials include piezoelectric ceramics, ferroelectric polymers and shape memory alloys, which exhibit strong mechanical-X coupling, where X can be electrical, magnetic or thermal stimuli. These materials can be used, for example, in precision fuel injectors to increase energy efficiency of diesel engines, in energy harvesting devices to power remote or portable electronics, as part of intelligent systems in manufacturing for better automation and energy-efficiency and in biomedical devices for high-resolution diagnostic imaging, minimally invasive surgeries and more efficient drug delivery.
The current challenges for developing new smart materials are to make them environmentally friendly, biologically compatible and easy to manufacture, while at the same time maintaining their enhanced functionality and long-term stability. In order to meet these varied challenges, a fundamental understanding of their processing-structure-property relationships is necessary, which I undertake with the aid of advanced X-ray and neutron scattering techniques. A particular focus is to understand the organization and effects of structural disorders at different length scales, such as localized atomic displacements, ferroelectric and ferromagnetic domains, domain walls and twin boundaries. Through direct observation of external-stimuli-induced structural changes in situ over length-scales spanning from nano-to-millimeters and over timescales spanning from picoseconds-to-minutes, the goal is to identify the key parameters that influence the physical phenomena in materials. This in turn provides new design concepts for developing materials with enhanced functionalities and durability.
The current challenges for developing new smart materials are to make them environmentally friendly, biologically compatible and easy to manufacture, while at the same time maintaining their enhanced functionality and long-term stability. In order to meet these varied challenges, a fundamental understanding of their processing-structure-property relationships is necessary, which I undertake with the aid of advanced X-ray and neutron scattering techniques. A particular focus is to understand the organization and effects of structural disorders at different length scales, such as localized atomic displacements, ferroelectric and ferromagnetic domains, domain walls and twin boundaries. Through direct observation of external-stimuli-induced structural changes in situ over length-scales spanning from nano-to-millimeters and over timescales spanning from picoseconds-to-minutes, the goal is to identify the key parameters that influence the physical phenomena in materials. This in turn provides new design concepts for developing materials with enhanced functionalities and durability.
Discovery of New Lead-free Ferroelectric Oxides from Insights into Nanoscale Atomic Ordering and Dynamics
Ferroelectric ceramics are highly attractive as piezoelectric, electrocaloric, energy-storage and energy-harvesting materials , which can be used in smart applications such as sensors, actuators, medical diagnostic imaging, microfluidic biomedical devices, 3D printing, high-density energy storage and vibrational energy harvesting. Due to environmental concerns regarding the current lead-based ferroelectrics, there have been tremendous efforts in recent years for searching lead-free alternatives. Our recent experiments with advanced X-ray and neutron scattering techniques provide fundamental insights into the central role played by nanoscale atomic correlations towards enhanced enhanced functional properties in lead-free perovskite (ABO3) ferroelectrics. We are exploring fundamental physico-chemical principles correlating macroscopic functional properties and nanoscale atomic ordering and dynamics to build a more rational basis for development of new environmentally friendly lead-free ferroelectrics. We are also using advanced synthesis methods to tailor desired microstructure in these materials.
Polar nano regions are formed in perovskite ferroelectrics due to nanoscale ordering among off-centered atomic displacements, such as shown on right. Such nanoscale correlations give rise to diffuse scattering signatures, and therefore their rearrangement could be monitored from in situ X-ray scattering experiments such as shown on the right.
Polar nano regions in perovskite ferroelectric solid-solutions are also dynamic in nature and their stabilization is essential for enhanced properties. The atomic correlations within polar nano regions and the dynamics of such clusters can be directly measured using advanced diffraction techniques, such as illustrated above.
Relevant Publications
- Pramanick, Dmowski, Egami et al., “Stabilization of polar nano regions in lead-free ferroelectrics”, submitted
- Pramanick et al., “Nanoscale atomic displacements ordering for enhanced piezoelectric properties in lead-free ABO3 ferroelectrics”, Advanced Materials 27, 4330 (2015), DOI: 10.1002/adma.201501274
- Pramanick et al., “Origins of large enhancement in electromechanical coupling for non-polar directions in ferroelectric BaTiO3”, Physical Review B: Rapid Communications 88, 180101 (2013) DOI: 10.1103/PhysRevB.88.180101