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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><h2><span style='font-family:"Tahoma","sans-serif"'>MS Thesis Announcement<o:p></o:p></span></h2><p class=MsoNormal><b><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:14.0pt;font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:14.0pt;font-family:"Tahoma","sans-serif"'>Nanoindentation Based Estimates of Flexoelectric Properties of Piezoelectric Crystals<o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:14.0pt;font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:14.0pt;font-family:"Tahoma","sans-serif"'>Cody R. Robinson<o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><span style='font-family:"Tahoma","sans-serif"'>April 16, 2012, 9:30am, Eng. Bldg. 1 Room 208 (Small MECE conference Rm)<o:p></o:p></span></p><p class=MsoNormal align=center style='text-align:center'><span style='font-family:"Tahoma","sans-serif"'>Committee: Dr. Ken White, Dr. Pradeep Sharma, Dr. Ashutosh Agrawal<o:p></o:p></span></p><p class=MsoNormal align=center style='text-align:center'><b><span style='color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal style='text-indent:.5in'><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal style='text-indent:.5in;line-height:150%'><span style='font-family:"Tahoma","sans-serif"'>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 (LiNbO<sub>3</sub>, LiTaO<sub>3</sub>, and 0.7Pb(Mg<sub>0.33</sub>,Nb<sub>0.67</sub>)O<sub>3</sub>-0.3PbTiO<sub>3</sub>) and to compare indentation data for indenters of Berkovich, cone, and cube corner geometry. Quartz and BaTiO<sub>3</sub> 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<sup>-9</sup>C/m), moderate in LiNbO<sub>3</sub> and LiTaO<sub>3</sub> (~10<sup>-9</sup>-10<sup>-8</sup>C/m), and strong in BaTiO<sub>3</sub> and PMN-30%PT (~10<sup>-4</sup>C/m). Results for quartz agree with previous work, results for BaTiO<sub>3</sub> 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.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>