Structural and microstructural behaviour of SnO2 dense ceramics doped with ZnO and WO3

SnO2-based varistors doped with ZnO and WO3 were prepared by mixed oxide method. Experimental evidence shows that the increase in ZnO amount increases the volume and microstrain of unit cell while the WO3 promotes a decrease. The effect of ZnO and WO3 additives could be explained by the substitution of Sn4+ by Zn2+ and W6+. The addition of WO3 inhibits the grain growth due to the segregation in the grain boundary without influence in the densification of the samples. Besides that, an increase in the electrical resistance of the SnO2-ZnO-WO3 system was observed independent of the WO3 concentration. (c) 2005 Elsevier B.V. All rights reserved.

Relation between ambient humidity and ionic conductivity of poly(thionaphtheneindole): Behaviour as an amperometric humidity sensor

The electrical characteristics of oxidized poly(thionaphtheneindole) were investigated as a function of ambient relative humidity (r.h.). The current flowing through a pressed pellet of material between two massive gold electrodes plotted against voltage gives a wave-shaped curve with a halfwave potential at V = similar to 3 V. The current recorded at 4 V (plateau of the wave) is a sigmoidal function of r.h, with the inflexion point at similar to 60%. An interpretation of these findings is given, based on the influence of water on the dielectric constant of the material and on acid-base equilibrium between poly(thionaphtheneindole) and water, from which protons are produced. The behaviour of poly (thionaphtheneindole) as the active component of an amperometric humidity sensor is also reported.

ANISOTROPY OF ELECTRICAL-PROPERTIES IN ALPHA-FE2O3 CERAMICS

Electrical conductivity and thermoelectric power measurements carried out in a heamatite ceramic showed a strong anisotropy in directions normal and parallel to the uniaxial pressing direction. This behaviour is similar to that verified in alpha-Fe2O3 single crystal. The results suggest that the extended structural defects, generated during sintering, disturb the magnetic order on the (001) planes of alpha-Fe2O3 and limit the mobility of n type carriers.

Thermistor behaviour and electric conduction analysis of Ni-doped niobate ferroelectric: the role of multiple beta parameters

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrical and microstructural properties of CaTiO3-doped K1/2Na1/2NbO3-lead free ceramics

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nonlinear control in an electromechanical transducer with chaotic behaviour

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Piezoresponse force microscopy behaviour of Bi4Ti3O12 ceramics with various excess bismuth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dielectric behaviour of CaCu3Ti4O12-epoxy composites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)