Impurity centers in PbTiO3 single crystals: An electron-spin-resonance analysis.

Abstract

Impurities in a nominally undoped c-domain ${\mathrm{PbTiO}}_{3}$ single crystal have been studied by ESR in a wide temperature interval (4.2--700) K before and after light illumination. Several 3d-metal paramagnetic impurities substituting for ${\mathrm{Ti}}^{4+}$ (${\mathrm{Mn}}^{4+}$, ${\mathrm{Fe}}^{3+}$, and ${\mathrm{Ni}}^{3+}$), as well as light-induced centers (${\mathrm{Pt}}^{3+}$, ${\mathrm{Ti}}^{3+}$-${\mathrm{V}}_{\mathrm{O}}$-A [Pb] and ${\mathrm{Ti}}^{3+}$-A [Pb]) were revealed in the crystal. A comparison of the observed temperature dependence of the axial crystal field constant with a calculation based on a Newman model allows one to show that ${\mathrm{Mn}}^{4+}$ occupies an off-center position in the oxygen cage similarly to ${\mathrm{Ti}}^{4+}$, while ${\mathrm{Fe}}^{3+}$ remains centered at any temperature, its excess charge being compensated in the distant spheres. The temperature dependence of ${\mathrm{Ti}}^{4+}$ ion displacements obtained on the basis of ESR data analysis is in good agreement with neutron diffraction measurements and does not confirm recent x-ray-absorption fine-structure data on the ${\mathrm{Ti}}^{4+}$ off-center position at T>${\mathit{T}}_{\mathit{c}}$. The ${\mathrm{Ni}}^{3+}$ center and the light-induced titanium centers have not been considered previously. The ${\mathrm{Ti}}^{3+}$-${\mathrm{V}}_{\mathrm{O}}$-A [Pb] center models can be imaged as an electron on a titanium ion nearest to the oxygen vacancy and a defect on a neighboring Pb site (${\mathrm{F}}_{\mathit{A}}$-center model). It has been shown that ${\mathrm{Pt}}^{3+}$ and ${\mathrm{Ti}}^{3+}$-${\mathrm{V}}_{\mathrm{O}}$-A [Pb] are shallow donors based on an analysis of the temperature dependence of their ESR intensities. \textcopyright{} 1996 The American Physical Society.