Conductivity sensors perovskite materials

On the other hand, the theoretical performance of concentration electrochemical cells, based on perovskite materials with protonic and oxygen ion conduction properties, has been described as well [191]. Besides, a sensor for the detection of oxidizable gases that employs the production of a non-Nemstian electrode potential, using zirconia as the solid electrolyte, has been developed [192],... 

Proton conducting perovskite oxides are the subject of numerous current studies, as these materials have a potential use in a number of electrochemical applications, including fuel cells, electrochromic displays and hydrogen sensors. Perovskite... 

The considerable attention paid to other perovskites such as BaTiOj as oxygen sensors is a result of the fact that the conductivity of these materials can be independent of operating temperatures. It has been suggested that the Fermi level lies in the semiconductor gap far above the valence band, and the concentration and mobility of free charge carriers (holes) depend on the operating temperature under different signs. This effect compensates the temperature-induced variations of the conductivity and results in zero temperature coefficient of resistance (Rothschild et al. 2005). It was... 

Toda K, Kameo Y, Kurita S, Sato M (1996) Crystal structure determination and ionic conductivity of layered perovskite compounds NaLnTiO (Ln = Rare Earth). J Alloys Compd 234 19-25 Tomchenko AA, Harmer GP, Marquis BT, AUen JW (2003) Semiconducting metal oxide sensor array for the selective detection of combustion gases. Sens Actuators B 93 126-134 Tongpool R, Leach C, Freer R (2000) Temperature and microstructural dependence of the sensitivity of heterocontacts between zinc oxide and copper oxide in reducing environments. 1 Mater Sci Lett 19 119-121 Traqueia LSM, Marques FMB, Kharton VV (2006) Oxygen ion conduction in oxide materials selected examples and basic mechanisms. Bol Soc Esp Ceram 45(3) 115-121... 

These studies were not intended to seek a good ionic conductor but to confirm the conduction species to clarify the phenomena characteristic to the ferroelectric or pyroelectric materials. It should be noted that the conductivity of ferroelectric materials mentioned above is very low and most of the researchers in those days took no notice of the value of conductivity itself. Studies on highly conductive ionic conductors of perovskite-type compounds were started in the second half of the 1960s to search for a good oxide ion-conducting electrolyte for fuel cells and oxygen sensors. These are described in the following sections. 

Thin films, to attain enough sensitivity and response time, of oxide materials normally deposited on a substrate are typically used as gas sensors, owing to their surface conductivity variation following surface chemisorption [183,184], Surface adsorption on a Sn02 film deposited on alumina produces a sensitive and selective H2S gas sensor [185]. In addition, a number of perovskite-type compounds are being used as gas sensor materials because of their thermal and chemical stabilities. BaTi03, for example, is used as sensor for C02 [183],... 

The book explores various examples of these important materials, including perovskites, zeolites, mesoporous molecular sieves, silica, alumina, active carbons, carbon nanotubes, titanium dioxide, magnesium oxide, clays, pillared clays, hydrotalcites, alkali metal titanates, titanium silicates, polymers, and coordination polymers. It shows how the materials are used in adsorption, ion conduction, ion exchange, gas separation, membrane reactors, catalysts, catalysts supports, sensors, pollution abatement, detergency, animal nourishment, agriculture, and sustainable energy applications. 

Finally, it should be noted that numerous perovskite-related materials with relatively low oxygen ionic conductivity at 700-1200 K have been excluded from consideration in this brief survey, but may have potential electrochemical applications in fuel cell anodes, current collectors, sensors, and catalytic reactors. Further information on these applications is available elsewhere 1-4, 11, 159, 217-219]. 

The perovskites Lai xMxB 03.5 (M = Sr, B = Co, Cr, Fe, Mn) have been reviewed by Alcock et al. in terms of their stability in temperature and oxygen partial pressiue of operation as active sensor material, nonstoiehiometry, conductivity, and catalytic properties, and the effect of the strontium eontent, x. 

Materials with high proton or oxide ion conductivity are widely studied for their potential application as electrolytes in fuel cells, electrolysers, batteries, sensors, ete. [1-5], Acceptor doped perovskite-type oxides ABO3.5 where A is Sr, Ba and B is Ce, Zr are well-known high temperature proton conductors in wet atmosphere. It was found that the main factor responsible for the appearance of protons in the structure was the presence of oxygen vacancies. Upon hydration by equilibration with water vapor the oxygen vacancies may be filled by oxygen from water and, in accordance with dissociative mechanism of water dissolution, the hydroxide ions are formed. In this case the dissolution of water may be written [6] ... 

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