Measurement and Properties of the Oxide Ionic Conductivity of β- and δ-Phases in the Binary (Bi₂O₃)_1−x (Tb₄O₇) _x System

Abstract

The total conductivity (σ T ) in the β-phase and δ-Bi 2 O 3 doped with Tb 4 O 7 system was measured in the composition range between 1 and 30 mol% Tb 4 O 7 at different temperatures. According to the DTA/TG results, this tetragonal type solid solution was stable up to about ∼740 • C, and the solubility limit was found at ∼5 mol% Tb 4 O 7 in the β-phase; this fcc type solid solution was stable up to about ∼740 • C, and the solubility limit was found at ∼30 mol% Tb 4 O 7 in the δ-phase. All phases showed predominant oxide ionic conduction. It has been proposed that β-and δ-Bi 2 O 3 phases contain a large number of oxide anion vacancies and incorporated terbium cations at tetrahedral sites that affect the oxygen sublattice of the crystal structure.Keywords bismuth oxide, oxygen ionic conductivity, terbium oxide INTRODUCTIONSolid electrolytes are the most important components of solid-state electrochemical devices, which are becoming increasingly important for applications in energy conversion, chemical processing, sensing, and combustion control. Bismuth oxide systems exhibit high oxide ionic conductivity and have been proposed as good electrolyte materials for applications such as solid oxide fuel cell and oxygen sensors. However, due to their instability under low oxygen partial pressure conditions there has been difficulty in developing these materials as alternative electrolyte materials compared to state-of-the-art cubic stabilized zirconia electrolyte. Bismuth oxide and doped bismuth oxide systems exhibit a complex array depending on dopant concentration, temperature, and atmosphere. [1][2][3][4][5] Six polymorphs of Bi 2 O 3 have been reported in the literature: monoclinic α-Bi 2 O 3 , tetragonal β-Bi 2 O 3 , cubic (bcc) γ -Bi 2 O 3 , cubic (fcc) δ-Bi 2 O 3 , orthorhombic ε-Bi 2 O 3 , and triclinic

Synthesis, characterization and oxide ionic conductivity of β-type solid solution in bismuth oxide doped with ytterbium oxide binary system

“…Until now, researchers have reported six polymorphs of bismuth trioxide (Bi 2 O 3 ). These are monoclinic (α-Bi 2 O 3 ), body-centred cubic (bcc) (γ -Bi 2 O 3 ), face-centred cubic (fcc) (δ-Bi 2 O 3 ), tetragonal (β-Bi 2 O 3 ), triclinic (ω-Bi 2 O 3 ) and orthorhombic (ε-Bi 2 O 3 ) phases (Takahashi et al 1977;Harwig 1978;Sammes et al 1999;Leontie et al 2001;Chehab et al 2003;Crumpton et al 2003;Ozpozan and Çırçır 2012). The α-phase is stable at room temperature while other five forms are unstable crystal modifications that are formed at high temperatures.…”

Polymorphism and Visible-Light-Driven Photocatalysis of Doped Bi2O3:M (M = S, Se, and Re)

“…Thus, a plethora of synthetic approaches for δ-Bi 2 O 3 in the form of powders, − ,,,,− films, ,− nanosheets, and nanowires was developed. However, stabilization of pure δ-Bi 2 O 3 at room temperature is still a challenge; therefore, the application of the metastable modification is restricted to a low number of examples. − Stabilization of δ-Bi 2 O 3 to room temperature can be achieved by doping, but it must be kept in mind that incorporation of dopants into the crystal lattice of bismuth­(III) influences the physical properties and, for example, reduces the oxygen ion conductivity by several orders of magnitude. ,− In the last decades, numerous reports have dealt with the stabilization of δ-Bi 2 O 3 using a variety of main-group elements and transition metals (B, P, Ti, , V, − Fe, Y, , Nb, , Te, Ta, Ce, − Eu, Tb, Dy, , Er, − Tm, Yb, , Lu, and Th) and double-doping (Hf/Zr, Te/V, Y/Yb, Er/Nb, Er/Gd, Ho/Gd, Ho/Dy, Dy/W, Sm/Ce, Sm/Yb, La/Mo, Pr/Mo, Dy/Tm, Gd/Lu, , Yb/Dy, , Eu, or Tb/Th…”