Effects of doping of lead titanate with alkaline-earth elements

Solid solutions of the (Pb$_{1-\alpha_1-\alpha_2}$Sr$_{\alpha_1}$Ba$_{\alpha_2})$TiO$_{3}$ (0.02 $\le\alpha_{1}\le$ 0.36, 0.0073 $\le\alpha_{2}\le$ 0.1339) system with the ratio of Sr and Ba chosen so as to exclude the influence of the size factor on the lead titanate structure have been studied. The studies have been performed using X-ray powder diffraction (XRD), X-ray absorption spectroscopy (EXAFS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). It has been found that the removal of 2.5 at % Pb$^{2+}$, which presumably occupy oxygen octahedra, from the solid solution leads to a partial relieving of the crystal lattice stress that is observed as the decrease in the parameter $c$, $c/a$, and the unit cell volume, with parameter $a$ being unchanged. It has been shown that PbTiO$_{3}$ contains up to 5 at % of Pb$^{4+}$ ions at all the preparation conditions. The Sr and Ba atoms replace the Pb atoms in lead titanate in a narrow concentration range 0 $<(\alpha_{1}+\alpha_{2})\le$ 0.0273; at higher Sr and Ba concentrations, solid solutions SrPb$_{x}$Ti$_{1-x}$O$_{3}$ $\to$ Sr$_{1-y}$Ba$_{y}$Pb$_{x}$Ti$_{1-x}$O$_{3}$ are formed.