Discipline: Chemistry and Chemical Sciences
Subcategory: Materials Science
Room: Park Tower 8217
Sarah Rodriguez - California State University, San Bernardino
Co-Author(s): Dr. Kimberley Cousins, California State University, San Bernardino
Inorganic ferroelectric materials, such as Lead Zirconate Titanate (PZT), are used as memory in electronics due to their unique property of spontaneous polarization, measured in µC/cm. Materials which display ferroelectric behavior are a subclass of piezoelectric materials, which release an electrical charge after the application of mechanical stress. Electronic waste recycling can cause local water and food supplies to be contaminated with toxic chemicals such as heavy metals and expose e-waste workers to vapors and direct contact with these toxic materials. A substitution of organic ferroelectrics for traditional ones could reduce the amount heavy metals, like lead, in electronic recycling. The search for organic ferroelectrics with polarization comparable to that of traditional ferroelectrics has become an exciting field of study within the last decade. Polarization in charge transfer (CT) ferroelectrics is caused by a shift in electronic density from a donor molecule to an acceptor molecule in a dimer. In past research, 1,5-diaminonaphthalene p-chloranil (CANANP) was isolated as a candidate for further investigation based on the charge transfer it demonstrates. Behera, et al.1 predicted CANANP to be weakly ferroelectric (0.06 µC/cm2) based on Berry phase calculations performed on the crystal structure and a constructed pseudo centrosymmetric structure. In this study, a computational reassessment of polarization in CANANP was completed using Berry Phase analysis of calculations performed using Vienna Ab initio Simulation Package (VASP) on the same structures used by Behera, et al. The calculations were performed using Density Functional Theory and GGA-PBE functional. Analysis by square root of the sum of the squares of the two polarities predicts CANANP to have a remnant polarization of 8.23 µC/cm2. Co-crystals of CANANP were grown for experimental analysis using piezoresponse force microscopy (PFM), which showed the butterfly and hysteresis curves indicative of piezoelectric/ferroelectric behavior, respectively. Following the documented crystallization for CANANP produced small, bar shaped crystals with an average surface area of about 1.5 mm2, which are sufficient for examination by PFM. To test for a phase change (a change in the structure of the crystal lattice), larger crystals of at least 15 mm2 were required. Several methods to increase the crystal surface area were attempted, with two producing crystals over 25mm2 in surface area. These larger crystals are currently undergoing tests to quantify the remnant polarization of the system. References: Behera, R. K., Goud, N. R., Matzger, A. J., Bredas, J., Coropceanu, V. Electronic Properties of 1, 5-Diaminonaphthalene: Tetrahalo-1, 4-benzoquinone Donor-Acceptor Cocrystals. J. Phys. Chem. 2017 121 (42), 23633-23641
Funder Acknowledgement(s): Funding for this project was awarded by the National Science Foundation to Dr. Timothy Usher, California State University San Bernardino. Supercomputing allocation awarded to Dr. Kimberley Cousins by Extreme Science and Engineering Discovery Environment (XSEDE).
Faculty Advisor: Dr. Kimberley Cousins, email@example.com
Role: I grew the crystals used for experimental research, including augmentation of the published literature for more desirable crystal size. I also ran the calculations and conducted the analysis of the calculations.