The Bi2O3–Sm2O3 system: phase diagram and electrical properties

Abstract

The (Bi₂O₃)_{1 –x}–(Sm₂O₃)_x system (0 ≤x≤ 0.65) was investigated by means of X-ray diffractometry, differential thermal analysis, impedance spectroscopy and e.m.f. measurements. The corresponding equilibrium solid-phase part of the diagram is proposed. The most striking feature is the existence of a very large domain of a δ Bi₂O₃ f.c.c.-type solid solution. By air-quenching from this domain two different phases were obtained: for 0.03 ≤x≤ 0.07, the room-temperature quenched phase exhibits tetragonal symmetry, changing to cubic for greater values of x. Both these phases are metastable and decompose into equilibrium phases on annealing. This transformation is always accompanied by a significant decrease in the electrical conductivity.