Magnetic and ferroelectric characteristics of Gd³⁺ and Ti⁴⁺ co-doped BiFeO ₃ ceramics

Abstract

Polycrystalline BiFeO$_{\mathrm {\mathbf {3}}}$ and Bi$_{\mathrm {\mathbf {0.9}}}$Gd$_{\mathrm {\mathbf {0.1}}}$Fe$_{\boldsymbol {1-}\boldsymbol {{x}}}$Ti _x O ₃ (x = 0, 0.01, 0.05 and 0.1) samples were synthesized by solid-state reaction route. Structural, magnetic and ferroelectric properties of these samples were investigated. X-ray powder diffraction (XRD) results confirmed the presence of a significant amount of Bi$_{\mathrm {\mathbf {2}}}$Fe$_{\mathrm {\mathbf {4}}}\textit {O}_{\mathrm {\mathbf {9}}}$ impurity phase in the undoped BiFeO$_{\mathrm {\mathbf {3}}}$ sample. Mössbauer spectroscopy studies corroborated the XRD studies to confirm the presence of impurity phase. We have observed that gadolinium (Gd$^{\boldsymbol {3+}}$) and titanium (Ti$^{\boldsymbol {4+}}$) doping, respectively, on Bi$^{\boldsymbol {3+}}$ and Fe$^{\boldsymbol {3+}}$ sites facilitated a significant reduction in the impurity phase formation in BiFeO$_{\mathrm {\mathbf {3}}}$. Interestingly, Gd$^{\boldsymbol {3+}}$-doping significantly reduced the impurity phase formation as compared to the undoped BiFeO$_{\mathrm {\mathbf {3}}}$ sample. This impurity phase formation was further overcome by doping higher (x $\boldsymbol {\ge }$ 0.05) amounts of Ti in BiFeO$_{\mathrm {\mathbf {3}}}$. The crystallographic site occupancies of Gd and Ti were confirmed by Rietveld refinement of XRD data, Mössbauer spectroscopy and magnetization measurements. An enhancement in ferromagnetic properties along with moderate ferroelectric properties have been observed after co-doping. There was an increasing trend in remnant polarization (P $_{\mathrm {\mathbf {r}}}$) with the increase in Ti concentration besides an improvement in the characteristic saturation magnetization. Our results demonstrate that Gd$^{\boldsymbol {3+}}$ and Ti$^{\boldsymbol {4+}}$ doping could be used to enhance multifunctional properties of BiFeO$_{\mathrm {\mathbf {3}}}$ ceramics to enable them as potential material for various devices.