AVS 49th International Symposium
    Processing at the Nanoscale Thursday Sessions
       Session PN+SS-ThM

Paper PN+SS-ThM11
Size-Induced Ferroelectric Phase Transitions in PbTiO@sub 3@ and PbZrO@sub 3@ Nanotubes Formed by Sol-Gel Template Synthesis

Thursday, November 7, 2002, 11:40 am, Room C-109

Session: Patterning and Functionalization
Presenter: B.A. Hernandez, Colorado State University
Authors: B.A. Hernandez, Colorado State University
K.-S. Chang, Colorado State University
E.R. Fisher, Colorado State University
P.K. Dorhout, Colorado State University
Correspondent: Click to Email
Nanotubes of the perovskite ABO@sub@3 (A = Pb, B = Ti,Zr) have been prepared by sol-gel template synthesis. A size-induced ferroelectric phase transition for PbTiO3 and PbZrO3 nanotubes was observed by thermal analysis. The nanotubes were prepared within Whatman Anodisc templates (200 nm pore size) with a sol-gel method using titanium and zirconium alkoxides and lead acetate. Scanning electron microscopy demonstrated that the structures formed within the template were 50 μm long tubes with 200 nm outer diameters. Transmission electron microscopy and electron diffraction revealed that the tubes were polycrystalline. Comparison of the d-spacing between electron and bulk powder X-ray diffraction patterns allowed assignment of the crystalline phase of the nanotubes as tetragonal for PbTiO3. Differential scanning calorimetery was used to monitor the ferroelectric phase transition temperature (Tc). Comparison between the bulk powders and nanotubes showed an anomalous decrease Tc. Values for PbTiO3 Tc were determined to be between 496.5°- 489.7°C for bulk powders with grain sizes of 75 and 35 nm respectively and 234.4°C for the nanotubes having a grain size of 11.2 nm. Preliminary results for PbZrO3 shows that the Tc decreases from 229.9 for bulk powder to 123.6 for nantRoom temperature Raman spectra also indicated structural size effects by monitoring the energies of the E1(TO) soft mode and relative intensities of the E2(TO) mode.