SnO2 varistors prepared through different synthesis routes

M.A. RAMÍREZ; R. PARRA; A. MOSQUERA,; J.E. RODRÍGUEZ PÁEZ; M.S. CASTRO; J.A. VARELA

Guarujá, Brasil

Simposio; SBPMat 2008; 2008

Sociedad Brasilera de Materiales

Varistors are electroceramic devices whose function is to sense and limit transient voltage surges. SnO2-based powders are mainly produced by means of the mixed oxide route1, coprecipitation22-based powders are mainly produced by means of the mixed oxide route1, coprecipitation2 and polymeric precursor methods3-4. However, the characteristics of the devices are greatly influenced by the selected precursors and synthesis method. In this work, SnO2- doped powders were prepared through different routes in order to evaluate their influence on the microstructure development and on the electrical properties. Co, Ti, Cr, Nb and Al were the selected additives to promote densification and to enhance the non-linear electrical behavior. Powders were pressed into discs by uniaxial and/or isostatic techniques and sintered at 1300 or 1350ºC. Silver electrodes were deposited on the samples faces for electrical characterization and current-voltage curves were acquired at room temperature by means of a Kithley 237 high-voltage source-measure unit. Although wet methods of synthesis yielded powders with much smaller particles, which may be sintered at lower temperatures, the mixed oxides route is straightforward and led to excellent electrical properties.3-4. However, the characteristics of the devices are greatly influenced by the selected precursors and synthesis method. In this work, SnO2- doped powders were prepared through different routes in order to evaluate their influence on the microstructure development and on the electrical properties. Co, Ti, Cr, Nb and Al were the selected additives to promote densification and to enhance the non-linear electrical behavior. Powders were pressed into discs by uniaxial and/or isostatic techniques and sintered at 1300 or 1350ºC. Silver electrodes were deposited on the samples faces for electrical characterization and current-voltage curves were acquired at room temperature by means of a Kithley 237 high-voltage source-measure unit. Although wet methods of synthesis yielded powders with much smaller particles, which may be sintered at lower temperatures, the mixed oxides route is straightforward and led to excellent electrical properties.2- doped powders were prepared through different routes in order to evaluate their influence on the microstructure development and on the electrical properties. Co, Ti, Cr, Nb and Al were the selected additives to promote densification and to enhance the non-linear electrical behavior. Powders were pressed into discs by uniaxial and/or isostatic techniques and sintered at 1300 or 1350ºC. Silver electrodes were deposited on the samples faces for electrical characterization and current-voltage curves were acquired at room temperature by means of a Kithley 237 high-voltage source-measure unit. Although wet methods of synthesis yielded powders with much smaller particles, which may be sintered at lower temperatures, the mixed oxides route is straightforward and led to excellent electrical properties.