Improvement in varistor properties of CaCu3Ti4O12 ceramics by chromium addition

• Published in: Journal of materials science & technology Vol. 41; pp. 12 - 20
• Main Authors: Grzebielucka, Edson Cezar, Leandro Monteiro, João Frederico Haas, de Souza, Eder Carlos Ferreira, Ferreira Borges, Christiane Philippini, de Andrade, André Vitor Chaves, Cordoncillo, Eloísa, Beltrán-Mir, Héctor, Antunes, Sandra Regina Masetto
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-03-2020
• Subjects: CCTO; Impedance; Rietveld; Structural analysis; Varistor; Varistor; CCTO; Impedance; Rietveld; Structural analysis
• ISSN: 1005-0302; 1941-1162
• DOI: 10.1016/j.jmst.2019.08.055

[Display omitted]
•Add of chromium to CaCu3Ti4-xCrxO12 (CCTO) system.•The substitution of Cr(III) on the Ti(IV) site occurs for maximum of 0.025 mol %.•Low concentration of Cr (0.025 mol %) increase the nonlinearity coefficient.•Low concentration of Cr (0.025 mol %) increase electric breakdown field strength.•The CaCu3Ti3.975Cr0.025O12-δ present potential to varistor application.
The effect of chromium addition on the structure and electrical properties of CaCu3Ti4O12 is studied. Compositions based on the formula CaCu3Ti4-xCrxO12-δ (x = 0, 0.025, 0.050 and 0.075 mol%) are prepared by solid-state reaction. Pellets sintered at 1070 °C for 12 h are characterised by X-ray diffraction, scanning electron microscopy/energy dispersive spectroscopy and impedance spectroscopy. Current density-electric field, dielectric loss and permittivity measurements are also carried out. Rietveld refinement showed the substitution of Cr(III) on the Ti(IV) site, with the maximum substitution for x = 0.025 mol%. The generation of electrical defects in the grain boundary region by chromium doping is responsible for increasing the electric breakdown field strength and nonlinearity coefficient at room temperature from 1723 V/cm and 5.29 for x = 0 mol% to 3431 V/cm and 8.16 for x = 0.025 mol%. This composition shows the greatest improvement in ceramic varistor parameters.