Research Projects

Crystallographic symmetry plays a vital role in defining the properties of Materials. Breaking of inversion symmetry allows the emergent functionalities like ferroelectric, piezoelectric, pyroelectric, second-order non-linear optical and multiferroicity. Ferroelectrics are a class of materials that exhibit reversible spontaneous polarization under the application of the electric field. This characteristic makes it unique for non-volatile memory storage applications called ferroelectric random-access memory (FeRAM). Other benefits include are fast access time, low read/write voltage, and a negligible standby current. However, the available conventional perovskite-based materials (Pb(Zr, Ti)O3 and SrBi2Ta2O9) shows serious concerns with the compatibility issues with complementary metal-oxide-semiconductor (CMOS) technology such as poor thin film deposition using ALD techniques, property reduction due to miniature thickness, defect generation due to loss of volatile elements.. etc. Park et al. (Science, 2022) have recently reported a breakthrough of piezoelectricity in the thin films of centrosymmetric Gd-CeO2 oxides. The thin films of Gd-CeO2 show a giant piezoelectric response of d33 ~200,000 pm/V with a piezo-strain of ~ 26%. The values are two to three orders of magnitude larger than that of best piezoelectric materials. This binary oxide has emerged as an alternative to perovskite-based materials. Practically, this simple oxide has numerous benefits compared to conventional materials regarding low deposition thickness (in nm scale), simple composition, compatibility with CMOS technology. However, though the system has inspired many researchers, there is a great need to study in detail the mechanisms at different length scales (unit cell as well as nano/micro) responsible for the ferroelectric response in this thin film. This requires not only understanding the subtle structural features in the zero-field state but also equally important to study how an electric field affects the structural (lattice and phase transformation behavior) and the microstructural (non-180 degree domain wall dynamics) states. During my investigation, along with measuring the piezo and pyroelectric properties on thin films, I intend to carry out detailed in-situ, ex-situ electric field and temperature-dependent scattering, diffraction, and microscopy studies on the famous thin film samples. These new experiments will contribute significantly towards understanding the microscopic mechanism(s) at play in this interesting system and will help design new binary oxide ferroelectric thin films. In the second part of the project (20-25% of project time), a serious effort will be devoted to finding ways to stabilize the piezoelectric phase in bulk polycrystalline ceramics using novel sintering techniques like Spark plasma sintering or Flash sintering. Both the studies would be the first of their kind on this type of system and have not been done till now.