Oxide Ion-Conducting Materials Containing Tetrahedral Moieties: Structures and Conduction Mechanisms

Abstract

This Review presents an overview from the perspective of tetrahedral chemistry on various oxide ion-conducting materials containing tetrahedral moieties which have received continuous growing attention as candidates for key components of various devices, including solid oxide fuel cells and oxygen sensors, due to the deformation and rotation flexibility of tetrahedral units facilitating oxide ion transport. Emphasis is placed on the structural and mechanistic features of various systems ranging from crystalline to amorphous materials, which include a variety of gallates, silicates, germanates, molybdates, tungstates, vanadates, aluminates, niobate, titanates, indium oxides, and the newly reported borates. They contain tetrahedral units in either isolated or linked manners forming different polyhedral dimensionality (0 to 3) with various defect properties and transport mechanisms. The development of oxide ion conductors containing tetrahedral moieties and the elucidation of the roles of tetrahedral units in oxide ion migration have demonstrated diverse opportunities for discovering superior electrolytes for solid oxide fuel cells and other related devices and provided useful clues for uncovering the key factors directing fast oxide ion conduction.

Optimizing Low-Temperature Ceramic Fuel Cells with CuFe2O4–CeO2 Heterostructures

“…This accounts for why CFO-CeO 2 exhibits lower resistance (both bulk and grain boundary) compared to as-prepared CeO 2 and CFO (see Figure a–c) . Moreover, creating a composite heterostructure with multiple active sites facilitates efficient charge carrier concentration at the surface and interface . Fitted parameters of 5CFO-5CeO 2 have been displayed in Table…”

High Conductivity and Diffusion Mechanism of Oxide Ions in Triple Fluorite-Like Layers of Oxyhalides

“…The reduction of Bi oxides into Bi metal can occur at lower P(O 2 ) than 10 −13 atm because the P(O 2 ) for the Bi/Bi 2 O 3 equilibrium is of the order of 10 −13 atm. 50 In contrast, Bi 1.9 Te 0.1 LuO 4.05 Cl showed a wider 39 Ce 0.9 Gd 0.1 O 1.95 , 46 (ZrO 2 ) 0.92 (Y 2 O 3 ) 0.08 , 5 La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 , 47 (Yb 0.9 Ca 0.1 ) 2 Ti 2 O 7 , 48 La 9.5 (Ge 5.5 Al 0.5 O 24 )O 2 , 49 Bi 3.9 Sr 0.1 NbO 8−δ Cl, 27 and CsBi 2 Ti 2 NbO 10−δ . 31 The black dotted line denotes the conductivity of 0.01 S cm −1 , and the yellow area stands for the region where the conductivity is higher than 0.01 S cm −1 .…”

“…(2) The parent materials Bi 2 R O 4 Cl and Bi 6–2 x Te 2 x O 8+ x Br 2 ( x = 0.5) are the Sillén oxyhalides with the triple fluorite-like layers where the interstitial oxygen sites exist, leading to possible interstitialcy oxide ion diffusion. Recently, the oxide ion conduction via the interstitialcy diffusion has attracted attention due to the high conductivity (e.g., hexagonal perovskite-related oxides, ,− K 2 NiF 4 -type oxides, melilite-type oxides, , scheelite-type oxides, , and mayenite-type oxides). In the present work, Bi 1.9 Te 0.1 LuO 4.05 Cl was found to show high oxide ion conductivity and chemical and electrical stability.…”

The Langasite Family for the Development of Oxygen-Vacancy-Mediated Oxide Ion Conductors

“…Solid oxide fuel cells (SOFCs) are of particular importance to satisfy the growing energy demand because of their high safety, high energy and power densities, longer cycle life, and lower cost, and they can convert chemical energy into electrical energy. − Oxides with open structural frameworks are capable of accommodating interstitial oxide ions, which can be used as electrolytes or electrodes in intermediate temperature SOFCs and thus have been attracting great interest to develop new oxide ion conductors. , …”