[CCoE Notice] FW: MS thesis announcement

[Khator, Suresh]

MS Thesis Announcement


Nanoindentation Based Estimates of Flexoelectric Properties of Piezoelectric Crystals

Cody R. Robinson

April 16, 2012, 9:30am, Eng. Bldg. 1 Room 208 (Small MECE conference Rm)
Committee: Dr. Ken White, Dr. Pradeep Sharma, Dr. Ashutosh Agrawal


Flexoelectricity refers to coupling between strain gradients and polarization in crystalline dielectrics. A piezoelectric-flexoelectric indentation model has recently been developed which when used in conjunction with nanoindentation stiffness data allows for estimation of flexoelectric properties. Objectives of the present work are to use this method to produce flexoelectric estimates for three previously uncharacterized crystals (LiNbO3, LiTaO3, and 0.7Pb(Mg0.33,Nb0.67)O3-0.3PbTiO3) and to compare indentation data for indenters of Berkovich, cone, and cube corner geometry. Quartz and BaTiO3 serve as weak and strong flexoelectric reference materials, respectively. Nanoindentation tests were conducted on the five piezoelectric crystals and their flexoelectric properties estimated by fitting the analytical indentation model to the data. Flexoelectric properties are determined to be weak in quartz (<10-9C/m), moderate in LiNbO3 and LiTaO3 (~10-9-10-8C/m), and strong in BaTiO3 and PMN-30%PT (~10-4C/m). Results for quartz agree with previous work, results for BaTiO3 conflict somewhat, and those for the remaining materials are original but justifiable. No major unexpected deviations are observed between data sets for each material obtained with different indenters. The ability of the analytic model to capture size dependent stiffness attributable to flexoelectric effects is reinforced. The estimation methods are concluded to be useful in characterizing flexoelectric properties of certain types of dielectric crystals.





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