M. Alguero et al., Direct measurement of mechanical properties of (Pb,La)TiO3 ferroelectric thin films using nanoindentation techniques, J MATER RES, 16(4), 2001, pp. 993-1002
A procedure using nanoindentation with spherical tipped indenters is presen
ted that allows separation of elastic, anelastic, and plastic contributions
to the deformation of thin films. The procedure was demonstrated on a rang
e of lanthanum-modified lead titanate (Pb,La)TiO3 (PTL) ferroelectric thin
films. Indentation stiffness coefficients ranging from 110 to 147 GPa have
been obtained depending on the microstructure and orientation of the PTL fi
lms. This coefficient was equivalent to land so, can be directly compared w
ith) Young's modulus of a nontextured, unpoled ceramic when films do not pr
esent preferred orientation. The trends of the anelastic contribution with
the thickness, structure, microstructure, and stress level at the film/subs
trate interface of the films were consistent with it being produced by ferr
oelastic domain wall movement. Pore compaction was a major mechanism of pla
stic deformation for the PTL films. Grain size also affected plastic deform
ation, probably as a consequence of its correlation with intergranular poro
sity. The technique has a high spatial resolution (contact area < 10 <mu>m(
2) for the results presented here), which allowed the mechanical homogeneit
y of the films to be studied and inhomogeneities to be identified from thei
r mechanical response (elastic, anelastic, and plastic).