Small Amount Of Bi Research Articles

Electrical conduction of Bi4Ti3O12-doped BaTiO3 ceramics sintered at low temperature

Abstract BaTiO 3 ceramics with a small amount of Bi 4 Ti 3 O 12 were sintered at a low temperature of 1100 °C for 2 h. We report a high densification of the system (BaTiO 3 + x Bi 4 Ti 3 O 12 ; 0.01 ≤ x ≤ 0.03) larger than 90% of BaTiO 3 theoretical density except for x = 0.01. We show the measured ac impendances of the samples at ≈ 500 °C using the complex plane plotting technique. The results involving large differences between the material resistance are discussed in terms of the final microstructure after the sample firing.

Luminescence of Bi 3+ ions and energy transfer from Bi 3+ ions to Eu 3+ ions in silica glasses prepared by the sol-gel process

Luminescence of Bi 3+ ions and energy transfer from Bi 3+ ions to Eu 3+ ions in silica glasses prepared by the sol-gel process have been investigated. The results showed that the excitation band of Bi 3+ ions corresponds to the 1S 0 → 1P 1 transition and emission spectra consists of a single broad band without structure centred at 395 nm, which corresponds to 3P 1 → 1S 0 transition. When a small amount of Bi 3+ ions was introduced to 1 mol% Eu 3+ ions the doped silica gel glass emission intensity of Eu 3+ ions got significantly stronger, which suggests very efficient energy transfer from Bi 3+ ions to Eu 3+ ions. It can be assigned to significant energy overlap between the emission band of the Bi 3+ ion and the excitation band of the Eu 3+ ion. However, due to a larger energy overlap between emission and excitation bands of Bi 3+, when Bi 3+ ion concentration in silica gel glasses was more than 0.5 mol% the probability of energy transfer between Bi 3+ ions increased rapidly and the probability of energy transfer from Bi 3+ ions to Eu 3+ ions decreased relatively. As a consequence, the sensitized effectiveness of the Bi 3+ ion on the emission spectrum of the Eu 3+ ion drastically decreased with increasing Bi 3+ ion concentration.

Qualitative study on the reaction of Bi 1.8Pb 0.4Ca 2Sr 2Cu 3O y superconductor with water

When Bi 1.8Pb 0.4Ca 2Sr 2Cu 3O y powders were immersed into deionized water, a large quantity of Ca 2+ and Sr 2+ ions was detected in the aqueous solution, indicating the decomposition of the Bi 1.8Pb 0.4Ca 2Sr 2Cu 3O y superconductors in water. The pH of the solution was initially increased rapidly to 11.1 due to the formation of OH - ions. However, after 30 min, in the open system, the Ca 2+ and Sr 2+ ions would further react with CO 2 in the atmosphere to form sparingly soluble carbonates and the pH of the solution was slowly decreased to 9.81 over 20 h. Only a small amount of Bi 3+, Pb 2+ and Cu 2+ ions was detected in the aqueous solution. Non-soluble products, such as Bi 2CuO 4, CuO and Cu 6PbO 8, were observed in the reaction residue which might act as a barrier to prevent deterioration of the superconductor with water in the bulk sample. The chemical equation was given as Bi 1.8Pb x Ca 2Sr 2Cu 3O y(s)+4H 2O→2Ca 2+ (aq)+2Sr 2+ (aq) +8OH - (aq)+0.9Bi 2CuO 4(s)+ xCu 6PbO 8(s) +(3−0.9−6 x)CuO (s).

Liquid metals and semiconductors under pressure

Studies on the electronic and thermodynamic properties of liquid metals and semiconductors at high temperatures and high pressures are reviewed. A substantial decrease of volume for liquid alkali metals is brought about by the application of pressure. The interference function of liquid alkali metals with high pressure can be described by the hard-sphere model with a fixed packing fraction when one proceeds along the melting curve. For liquid Cs, the s–d resonance scattering plays an important role in the electron-transport properties at high pressures. In expanded liquid Hg, a metal–nonmetal transition occurs at a density near 9 g∙cm−3, and anomalous behaviour is found in the thermodynamic properties such as equation-of-state and density fluctuations. At low densities, substantial volume contraction and a large increase in conductivity are brought about by the addition of a small amount of Bi. At high temperatures and high pressures, liquid Se is transformed from a semiconducting state to a metallic state, accompanied by modification of chain structure. The measurements of sound velocity and optical properties reveal that the temperature and pressure at which the semiconductor–metal transition occurs are lowered by the addition of Te. It is suggested that the semiconductor–metal transition observed in liquid Se is induced by increasing fluctuations in the interchain distance and increasing interchain coupling. The electronic properties of liquid Se are substantially changed by the addition of impurity elements such as alkalis and halogens. Modification of chain structure is associated with the charge transfer between Se chains and impurity elements. To understand how the interchain coupling affects the electronic properties of liquid Se, the properties of the isolated Se chains confined in the pores of mordenite are studied. The pressure effects on the two-phase separation of liquid binary mixtures, such as metal–metal, metal–semiconductor, and metal – ionic salt mixtures, are also discussed.

Magnetic properties and pressure effects on CeBi xSb 1−x and CeSb xAs 1−x single crystals

Unusual variation of the Néel temperature, T N, of CeSb and change of easy magnetization axis is observed when Sb is substituted by a small amount of Bi or As. T N increases with pressure and its variation is maximum for CeSb. Results are interpreted as a decrease of the crystalline field splitting with pressure.