<b>Effect of Pr₆O₁₁ doping in electrical and microstructural properties of SnO₂-based varistors<b>

• Main Authors: Hervê Stangler Irion, Eder Carlos Ferreira de Souza, André Vitor Chaves de Andrade, Sandra Regina Masetto Antunes, Augusto Celso Antunes
• Format: Article
• Language: English
• Published: Universidade Estadual de Maringá 2014-04-01
• Series: Acta Scientiarum: Technology
• Subjects: characterization; tin dioxide; praseodymium oxide; tantalum oxide
• Online Access: http://186.233.154.254/ojs/index.php/ActaSciTechnol/article/view/17995
• ISSN: 1806-2563; 1807-8664

The influence of the dopant Pr6O11 was investigated with regard to the electrical and microstructural properties of the system (98.95-x)%SnO2.1.0%CoO.0.05%Ta2O5.x%Pr6O11, where x = 0.05%, 0.10%, 0.30% and 0.50% in mol. Pr6O11 doping modifies the electrical behavior of the ceramics. The electrical parameters were: α = 8.0, EB = 319 V cm-1 and Vb = 0.66 V barrier-1 for the system without Pr6O11 and α = 17.0, EB = 853 V cm-1 and Vb = 1.15 V barrier-1 with the addition of 0.10% in mol Pr6O11. The system with 0.05% in mol Pr6O11 had the same non-linearity coefficient α as the system with 0.10% in mol. However, breakdown electrical field and voltage per barrier rates were lower (EB = 708 V cm-1 and Vb = 0.98 V barrier-1). The low rates in the breakdown electrical field enabled the varistor systems under study to be used in protection systems for low-voltage energy grids. In the case of Pr6O11 concentrations above 0.10% in mol, the presence of the dopant became deleterious to the varistor’s electrical characteristics. This effect was due to an increase in praseodymium stannate (Pr2Sn2O7) secondary phase. The crystalline phase coupled to the cassiterite (SnO2) phase was found with XRD and SEM/EDS and quantified by Rietveld’s refining method.