Analysis of Influence of Voltage on Potential Barrier on BiCuVOX and BiTiVOX Ceramics S.M. Gheno, 1,2, * V.L. Pimentel, 3 M.R. Morelli, 1 and P.I. Paulin Filho 1 1 UFSCar, Federal University of Sao Carlos, Department of Materials Engineering, Brazil 2 FATEC, Faculty Technology of Sertãozinho, Brazil 3 LNLS, Brazilian Synchrotron Light Laboratory (LNLS), Brazil Abstract: The BiMeVOx family of compounds appears to be more attractive for applications at low tempera- tures when ionic conductivity is the determining parameter. The objective of this study was to analysis the influence of voltage of the behavior of the Schottky barrier in both BiCuVOX and BiTiVOX.The samples were analyzed by atomic force microscopy and electric force microscopy ~EFM!. EFM experiments were conducted to map the electric field distribution on the surface. The formation of Schottky barriers was observed, and their height and width measured. BiCuVOX samples show a barrier width of 140 nm, and BiTiVOX shows a barrier width of 350 nm. The applied voltage has no effect on the barrier width but increases the peak height as observed in the cantilever frequency as measured with the EFM technique. Key words: BiCuVOX, BiTiVOX, grain boundaries, electric force microscopy ~EFM!, electrical properties, Schottky barrier I NTRODUCTION The growing demand for electricity, coupled with the need to reduce pollutant emissions, makes it necessary to develop new technologies that can effectively adapt alternative meth- ods to the process of electric power generation and distribu- tion. In this context, the use of fuel cells is very promising. Fuel cells are generally classified according to the type of electrolyte used and the temperature ~Subbarao & Maiti, 1984!. Electrolytes can be classified according to their ion transport and the nature of conductivity ~cation or anion! ~Murugesamoorthi et al., 1993!. Oxygen ion conductors, which are one of the most extensively studied anionic solid electrolytes, are employed in a wide variety of applications such as oxygen sensors and fuel cells ~Cross, 1998!, oxygen pumpsand air separators ~Minh, 1993; Cross, 1998!, solid oxide fuel cells ~Chmielowiec et al., 2009!, oxygen sensors ~Carolan et al., 1992; Chen et al., 1992!, and catalytic inorganic membrane reactors ~Gates et al., 1979; DiCosimo et al., 1986!. Their wide range of applications is due to the fact that these materials are able to block the passage of liquids and gases while simultaneously allowing ions to be transported through the network when there is a tendency for diffusion. Solid electrolytes, also known as fast ion conductors, are a class of materials with significantly higher low-temperature conductivity than would be expected from a simple statisti- cal assumption regarding the number of vacancies. Their measured oxide ion conductivities are quite high, and their transport number is near unity ~Emel’yanova et al., 2006; Kendall et al., 1996; Simner et al., 1997; Morelli et al., 1999!. Ceramic compounds with a perovskite-type structure based on bismuth vanadate ~Bi 4 V 2 O 11 ! show ionic conduc- tivities that are 50 to 100 times higher than any other oxygen ion conductor in the temperature range of 300 to 3508C. The BiMeVOX compounds ~where Bi represents bismuth, Me represents the metallic dopant ion, V is the vanadium atom, and OX is the oxygen! represent a large family of compounds in which Me may be Cu, Ni, Zn, Fe, Al, Sb, or Nb, which are used to stabilize the conducting phase at low temperatures and increase ionic conductivity ~Paulin Filho et al., 2000!. Abraham et al. ~1990! were the first to discuss the initial members of the BiMeVOx family, and their report spurred a flurry of other papers reporting various partial substitu- tions of other elements for the Bi, V, or both metals in the structure and the resulting modifications to the ionic conductivity. The high oxide ion conductivity reported for the BiMeVOx family is believed to be due to the disorder of the oxygen vacancies that are associated with the vana- dium atoms in the perovskitic layer. These authors demon- strated that the ionic conductivity of the formulation Bi 2 Cu 0.1 V 0.9 O 5.35 ~1  10 -2 s{cm -1 pellet pressed at 3008C! was about three orders of magnitude higher than that of YSZ at the same temperature. Some care in the preparation of materials to avoid octahedral coordination and formation of clusters is de- noted to the controller in the number of unfavorable tetrahedral V~V! sites, which causes the poor oxide ion conductivity of Cr ~III!-doped samples as reported by Del- maire et al. ~2000!, while Boivin and Mairesse ~1998! have summarized results for the substitutions of various metal cations onto the vanadium site. Many examples of this type of substitution have been reported ~Anne et al., 1992; Essalim et al., 1992; Joubert Received April 2, 2012; accepted December 7, 2012 *Corresponding author. E-mail: gheno@dema.ufscar.br Microsc. Microanal. 19, 688–692, 2013 doi:10.1017/S1431927613000160 Microscopy AND Microanalysis © MICROSCOPY SOCIETY OF AMERICA 2013