Bismuth sensor

Jeronimo P., Araujo A., Montenegro M., Satinsky D., Solich P., Colorimetric bismuth determination in pharmaceuticals using a xylenol orange sol-gel sensor coupled to a multicommutated flow system, Anal. Chim. Acta. 2004 504 235-241. 

Four solid oxide electrolyte systems have been studied in detail and used as oxygen sensors. These are based on the oxides zirconia, thoria, ceria and bismuth oxide. In all of these oxides a high oxide ion conductivity could be obtained by the dissolution of aliovalent cations, accompanied by the introduction of oxide ion vacancies. The addition of CaO or Y2O3 to zirconia not only increases the electrical conductivity, but also stabilizes the fluorite structure, which is unstable with respect to the tetragonal structure at temperatures below 1660 K. The tetragonal structure transforms to the low temperature monoclinic structure below about 1400 K and it is because of this transformation that the pure oxide is mechanically unstable, and usually shatters on cooling. The addition of CaO stabilizes the fluorite structure at all temperatures, and because this removes the mechanical instability the material is described as stabilized zirconia (Figure 7.2). 

The present chapter reviews recent research efforts aimed at developing new devices for in situ and on-site electrochemical stripping analysis of trace metals. It is not a comprehensive review, but rather focuses on new tools for decentralized metal testing, including remotely deployed submersible stripping probes, hand-held metal analyzers coupled with disposable microfabricated strips, and newly developed green bismuth film sensors. 

Fig. 7.1. Schematics of the GECEs used for stripping analysis of metals. (A) Sensing based on GECE sensors without modifications. (B) Sensing based on Bi-GECE. It represents GECE without modification but in the presence of bismuth in the measuring solution. (C) Sensing based on Bi(N03)3-GECE. It represents GEC modified internally with bismuth nitrate salt.

The developed bismuth-based GECE sensors compared to unmodified GECE show good stability which owing to the unique surface morphology results in enhanced contact between the GECE matrix... 

Biotin 629, 808 Biphasic system el45 Bipotentiostat 909 Bis(l-butylpentyl)adipate 60 Bis-pyrene 821 Bismuth electrodes 144 based metal sensor 136 Blood 6 electrolytes 5 gases 5 plasma 6... 

Bismuth is a rather rare element in the earth s crust, but its oxides and sulfides appear at sufficient concentrations as impurities in lead and copper ores to make its recovery from these sources practical. Annual production of bismuth amounts to several million kilograms worldwide. Although elemental bismuth is a metal, its electrical conductivity is quite poor and it is relatively brittle. The major uses of bismuth arise from its low melting point (271.3°C) and the even lower melting points of its alloys, which range down to 47°C. These alloys are used as temperature sensors in fire detectors and automatic sprinkler systems because, in case of... 

Courouau, J.-L. (2004) Electrochemical oxygen sensors for on-line monitoring in lead-bismuth alloys status of... 

Konys, J., Muscher, H., Vofi, Z. and Wedemeyer, O. (2004) Oxygen measurements in stagnant lead-bismuth eutectic using electrochemical sensors. J. Nucl. Mater, 335 (2), 249-53. 

The results of the present work may be applicable for diagnostics of oxygen sensors at more complicated applications, such as measurement of oxygen activity in liquid sodium, lithium, or lead-bismuth heat carriers for atomic power plants. Corrosion and mass transfer in nonisothermal lead-bismuth circuits with temperatures of a heat carrier of 300-500°C do usually occur at a concentration of dissolved O2 of 10 - 10 mass %. The proposed impedance method is developed for determining the level and the character of polarization at the electrolyte-electrode interface, which ensures a continuous oxide protection of materials against corrosion by means of zirconia sensors in all tanperature regimes of exploitation of liquid-metal circuits. 

Ceramics represent a vast outlet for bismuth compounds, particularly bismuth oxide. Small levels of inclusions have a remarkable impact on the performances of the materials used for electronics. Typical examples of electroceramics are those derived from sintered Bi203-3Sn02, Zn0 Bi203 or 2Bi203-3Ti02. Many of these ceramics can work as sensors for monitoring... 

Other materials, such as bismuth ferrites (BiFeOs, Bi4pe209, Bi2pe409) [14] have been studied as semiconductor materials for resistive gas sensors they respond as n-type semiconductors as with typical metal oxides. The changes in conductivity of these materials are due to a volume effect. In the absence of air, sensitivities to reducing gases such as petrol, ethanol, and acetone were at least an order of magnitude lower than under similar conditions with air present. 

Poghossian A S, Abovian H V, Avakian P B, Mkrtchian S H and Haroutunian V M 1991 Bismuth ferrites new materials for semiconductor gas sensors Sensors Actuators B 4 545-9... 

Complex FCC oxides of the fluorite type represent oxygen-conduction solid electrolytes (SOE s). They comprise a typical class of materials for the manufacture of sensors of oxygen activity in complex gas mixtures, oxygen pumps, electrolyzers and high-temperature fuel elements. These materials are based on doped oxides of cerium and thorium, zirconium and hafnium, and bismuth oxide. Materials based on zirconium oxide, for example, yttrium stabilized zirconia (YSZ) are the most known and studied among them. This fact is explained both by their processibility and a wide spectrum of practical applications and by the possibility to conduct studies on single crystals, which have the commercial name "fianites" and are used in jewelry. 

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