Pressure-induced decomposition of Bi14WO24

Abstract

We present a study of the high-pressure behaviour Bi₁₄WO₂₄, a high oxide ion conductor member of the Bi₂O₃-WO₃ binary system. The tetragonal polymorph of Bi₁₄WO₂₄ was studied under high-pressure conditions using synchrotron powder X-ray diffraction. It was found that in contrast to isostructural Bi₁₄CrO₂₄ and Bi₁₄MoO₂₄ which experience a phase transition around 5 GPa, in our study Bi₁₄WO₂₄ apparently undergoes an irreversible chemical decomposition into Bi₂O₃ and WO₃ at 2.85(5) GPa. The pressure dependence of the unit-cell parameters of Bi₁₄WO₂₄ 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 Bi₁₄WO₂₄ 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.