Synthesis and structural study of stoichiometric BiTi2O7 pyrochlore

Bi2Ti2O7 has been synthesized using a co-precipitation route from H2O2/NH3(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 470degreesC. Time-of-flight powder neutron diffraction studies of Bi2Ti2O7 (Space group Fd (3) over barm, a = 10.37949(4) Angstrom 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 2K