Synthesis and structural study of stoichiometric Bi2Ti2O7 pyrochlore

Bi₂Ti₂O₇ has been synthesized using a co-precipitation route from H₂O₂/NH_3(aq) solutions of titanium with aqueous bismuth nitrate. The stoichiometric material crystallizes into a pale yellow cubic pyrochlore phase. A powder X-ray diffraction study showed this crystallization to be very temperature sensitive, the pure phase can only be obtained within a few degrees of 470°C. Time-of-flight powder neutron diffraction studies of Bi₂Ti₂O₇ (Space group , a=10.37949(4) Å at ambient temperature, Z=8, R_p=3.95%, R_wp=4.75%) revealed positional disorder in the bismuth site and in the O′ oxide site both at ambient temperature and at 2 K.