Structural and magnetic properties of combustion synthesized $\hbox {A}_{2}\mathrm{Ti}_{2}\mathrm{O}_{7}$ ($\hbox {A} = \hbox {Gd}$, Dy and Y) pyrochlore oxides

Abstract

Nanostructured pyrochlore oxides $\hbox {A}_{2}\hbox {Ti}_{2}\hbox {O}_{7}$ ($\hbox {A} = \hbox {Gd}$, Dy and Y) have been synthesized through a single step auto-igniting citrate complex combustion process. The structure and phase formation of the prepared combustion product were characterized by X-ray diffraction (XRD) analysis. From the XRD patterns, the average crystallite size and lattice strain were calculated using the Williamson–Hall method. Pyrochlore oxides $\hbox {A}_{2}\hbox {Ti}_{2}\hbox {O}_{7}$ ($\hbox {A} = \hbox {Gd}$, Dy and Y) exhibit a cubic pyrochlore structure with the fd3m space group. The microstructure and average grain size of the samples were examined by scanning electron microscopy. The surface area and pore size of the materials were obtained from Brunauer–Emmett–Teller (BET) analysis. The obtained higher BET surface area of the $\hbox {Gd}_{2}\hbox {Ti}_{2}\hbox {O}_{7}$ material suggests the possibility of excellent photocatalyst activity. The vibrating sample magnetometer studies show that these materials show paramagnetic behaviour at room temperature. These materials have an entropy change that increases when the temperature decreases. So these materials may be used as active magnetic refrigerants at low-temperature.