Pressure-induced decomposition of Bi14WO24

• A high-pressure synchrotron powder x-ray diffraction study of Bi 14 WO 24 is reported. • Chemical decomposition is induced by pressure in Bi 14 WO 24 at 2.85 GPa. • The compressibility of Bi 14 WO 24 is determined and compared with related compounds. We present a study of the high-pressure behaviour Bi 14 WO 24 , a high oxide ion conductor member of the Bi 2 O 3 -WO 3 binary system. The tetragonal polymorph of Bi 14 WO 24 was studied under high-pressure conditions using synchrotron powder X-ray diffraction. It was found that in contrast to isostructural Bi 14 CrO 24 and Bi 14 MoO 24 which experience a phase transition around 5 GPa, in our study Bi 14 WO 24 apparently undergoes an irreversible chemical decomposition into Bi 2 O 3 and WO 3 at 2.85(5) GPa. The pressure dependence of the unit-cell parameters of Bi 14 WO 24 was also determined, and hence the linear compressibility along different axes and room-temperature pressure–volume equation of state were derived. Bulk modulus of tetragonal Bi 14 WO 24 was found to be 49.8(2.6) GPa, and the linear compressibility of the two crystallographic axes, κ a and κ c were 6.94(2) 10 −3 GPa −1 and = 3.73(1) 10 −3 GPa −1 , respectively. The pressure induced decomposition can be attributed to the favourable increasing density of the system to accommodate the pressure induced stress.