Crystal Structure and Characterization of La_1-xBi_xMnO_3+δ

Abstract

The La 1-x Bi x MnO 3+δ (x=0.0-0.5) solid solutions were synthesized using three different methods: solid-state synthesis, citrate-nitrate combustion synthesis. All compositions crystallize in a rhombohedral perovskite structure, independent of the synthesis method. Two ranges with linear temperature dependence of the unit cell parameters have been observed during in-situ heating Xray powder diffraction experiments. The transition between the two ranges occurs at 730°C and is explained by chemical expansion at high temperatures. The chemical compatibility between the obtained solid solutions and bismuth-containing electrolytes (Bi 4 V 1.7 Fe 0.3 O 11 , Bi 13 Mo 5 O 34 and Bi 3 Nb 0.8 W 0.2 O 7.1 ) was studied. Interaction between these materials has been observed at temperatures higher than 600°С. ExperimentalThe La 1-x Bi x MnO 3+δ (x=0.0-0.5; Δх=0.1) samples were synthesized via a solid-state route and a citrate-nitrate combustion method. For the solid-state synthesis, Bi 2 O 3 (99.9%), Mn 2 O 3 and La 2 O 3 (LaO-D) were used as initial compounds. Mn 2 O 3 was prepared by annealing MnO 2 (>85% purity) at 750°C. La 2 O 3 is highly hydroscopic so it was weighed immediately after annealing at 1000°C. The stoichiometric mixtures of the initial compounds were placed in the alumina crucibles and annealed in air in the temperature range T = 600-1200°С with intermediate cooling and regrinding in an agate mortar after each step of 100°С. For the citrate-nitrate combustion method, the initial metal oxides were dissolved separately in diluted nitric acid. Mn 2 O 3 was dissolved with adding small amount oxalic acid. Then as-prepared solutions were mixed with the ratio 1 : 2 (number of metal atoms : citric acid). Subsequent evaporation was performed at 80°C for 5 hours leading to the formation of solid precursors. The obtained precursors were annealed at 600°С and 1100°С (x=0.1-0.5) and 1200°С (x=0.0). Bismuth-containing electrolytes Bi 4 V 1.7 Fe 0.3 O 11 , Bi 13 Mo 5 O 34 and Bi 3 Nb 0.8 W 0.2 O 7.1 were synthesized using the solid-state method described elsewhere (1-3) to study their chemical compatibility with La 1-x Bi x MnO 3+δ electrodes.X-ray powder diffraction (XRD) patterns were collected using CuK α radiation on a D8 ADVANCE diffractometer equipped with a VÅNTEC position-sensitive detector and 10.1149/06801.0977ecst ©The Electrochemical Society ECS Transactions, 68 (1) 977-985 (2015) 977 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 139.80.123.42 Downloaded on 2015-07-23 to IP

Preparation, Structure and Physicochemical Properties of La0.95Bi0.05Mn1-yCuyO3+δ (у=0.1-0.4) and Composites with Bi2O3-Based Electrolytes

“…Crystal structure refinements were performed using full-profile Rietveld method. The oxygen nonstoichiometry (δ) was determined by redox potentiometric titration (automatic potentiometric titrator ATP-2 AKVILON) at room temperature [16]. A surface morphology and a local chemical composition of the powder and ceramic specimens fired at 1200-1270 °С were determined using scanning electron microscopy (SEM) on microscope JEOL JSM 6390LA (Jeol, Japan).…”