BiVO4 powder with scheelite structure was obtained by hydrolyzing a nitric acid solution of Bi(NO3)3 and Na3VO4 with bases (Na2CO3 and NaHCO3) at room temperature. Tetragonal BiVO4 of a high-temperature form was obtained after 4.5 h of preparation time while monoclinic BiVO4 was done after 46 h. Although the structure and the band gap of tetragonal BiVO4 with scheelite structure were similar to those of monoclinic BiVO4, the photocatalytic activity of the tetragonal BiVO4 for O2 evolution from an aqueous AgNO3 solution under visible light irradiation was negligible. In contrast, the monoclinic BiVO4 showed high photocatalytic activity. Distortion of a Bi−O polyhedron by a 6s2 lone pair of Bi3+ plays an important role for high photocatalytic activity of the monoclinic BiVO4 under visible light irradiation.

Selective Preparation of Monoclinic and Tetragonal BiVO4 with Scheelite Structure and Their Photocatalytic Properties

Bismuth oxide systems exhibit high oxide ion conductivity and have been proposed as good electrolyte materials for applications such as solid oxide fuel cells and oxygen sensors. However, due to their instability under conditions of low oxygen partial pressures there has been difficulty in developing these materials as alternative electrolyte materials compared to the state-of-the-art cubic stabilised zirconia electrolyte. Bismuth oxide and doped bismuth oxide systems exhibit a complex array of structures and properties depending upon the dopant concentration, temperature and atmosphere. In this paper we comprehensively review the structures, thermal expansion, phase transitions, electrical conductivity and stability of bismuth oxide and doped bismuth oxide systems. ©

Bismuth based oxide electrolytes— structure and ionic conductivity

Over the past decade, many efforts have been made to develop new materials exhibiting high oxide ion mobility at low temperature. In addition to the improvements of existing materials, new classes of conductors in which the structure have been shown to play an important role has been proposed. These materials are reviewed according to their structure type. Their performances and limitations are presented and discussed.

Recent Material Developments in Fast Oxide Ion Conductors

Recent advances in visible light Bi-based photocatalysts

Using density functional theory calculations, we analyze the optical absorption properties of lead (Pb)-free metal halide perovskites (AB2+X3) and double perovskites (A2B+B3+X6) (A = Cs or monovalent organic ion, B2+ = non-Pb divalent metal, B+ = monovalent metal, B3+ = trivalent metal, X = halogen). We show that if B2+ is not Sn or Ge, Pb-free metal halide perovskites exhibit poor optical absorptions because of their indirect band gap nature. Among the nine possible types of Pb-free metal halide double perovskites, six have direct band gaps. Of these six types, four show inversion symmetry-induced parity-forbidden or weak transitions between band edges, making them not ideal for thin-film solar cell applications. Only one type of Pb-free double perovskite shows optical absorption and electronic properties suitable for solar cell applications, namely, those with B+ = In, Tl and B3+ = Sb, Bi. Our results provide important insights for designing new metal halide perovskites and double perovskites for optoel...

Parity-Forbidden Transitions and Their Impact on the Optical Absorption Properties of Lead-Free Metal Halide Perovskites and Double Perovskites.

Structures and oxide mobility in Bi-Ln-O materials: heritage of Bi2O3.

The binary system PbO–BiVO4 exhibits two new phases, Pb4BiVO8 and Pb2BiVO6. They both melt congruently at 780 °C. They have been identified by single-crystal and powder X-ray diffraction. Pb4BiVO8 crystallizes with a triclinic cell, a= 6.221(2)A, b= 7.603(5)A, c= 10.457(4)A, α= 100.40(3)°, β= 102.18(2)°, γ= 90.03(3)° and Z= 2. Pb2BiVO6 exhibits four phase transitions at 300, 415, 475 and 600 °C. The α phase, room-temperature form, is monoclinic with a=7.642(6)A, b= 5.81 2(5)A, c= 28.85(2)A, β=100.3(1)° and Z= 8. The β and γ phases are orthorhombic with a= 8.381(6)A, b= 16.65(1)A, c= 4.859(6)A, Z= 4 and a=14.304(7)A, b=10.14(1)A, c= 9.923(4)A, Z= 8, respectively. The δ phase is tetragonal with a= 12.110(2)A, c= 9.472(8)A and Z= 8.

Michel Drache

Papers

Structures and oxide mobility in Bi-Ln-O materials: heritage of Bi2O3.

New phases in the binary system PbO–BiVO4: Pb2BiVO6 and Pb4BiVO8

Structural and Conductivity Properties of Bi0.775Ln0.225O1.5Oxide Conductors (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) with Rhombohedral Bi–Sr–O Type

A new family of compounds with tetrahedral anions: PbnBiOn(XO4), X = V, P, As, n = 1, 2, 4. A comparison with lead oxysulfates PbnPbOn(SO4)

Solid-state reaction pathways of Sillenite-phase formation studied by high-temperature X-ray diffractometry and differential thermal analysis