title: Dielectric behavior of ceramic-graphene composites around the percolation threshold.
abstract: Al2O3/graphene and BaTiO3/graphene composites with different concentrations of the conductive second phase, both below and above the percolation threshold, were prepared by the traditional ceramic processing route followed by spark plasma sintering. It is shown that the addition of graphene pins the grain growth of the ceramic matrix grains, leading to a change of the microstructure at low filler concentrations. As a consequence, the composites exhibit two percolation thresholds and their dielectric properties are not only determined by the dielectric properties of the constituents and their relative fractions but also the microstructure of the composite must be considered. Additionally, a giant increase of the dielectric constant has been found around the percolation thresholds in barium titanate-graphene composites. In particular, values of the dielectric constant up to 45,000 and 15,000 were found at 1 kHz in composites containing 0.4 and 0.6 wt. % graphene, respectively.
authors.affiliation: Centro de Investigación en Nanomateriales y Nanotecnología, Consejo superior de Investigaciones Científicas (CSIC)-Universidad de Oviedo (UO)-Principado de Asturias, Avenida de la Vega 4-6, El Entrego, 33940 San Martin del Rey Aurelio (Asturias) Spain.
authors.forename: Lucía
authors.initials: L
authors.lastname: Fernández-García
authors.affiliation: Centro de Investigación en Nanomateriales y Nanotecnología, Consejo superior de Investigaciones Científicas (CSIC)-Universidad de Oviedo (UO)-Principado de Asturias, Avenida de la Vega 4-6, El Entrego, 33940 San Martin del Rey Aurelio (Asturias) Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Suárez
authors.affiliation: Centro de Investigación en Nanomateriales y Nanotecnología, Consejo superior de Investigaciones Científicas (CSIC)-Universidad de Oviedo (UO)-Principado de Asturias, Avenida de la Vega 4-6, El Entrego, 33940 San Martin del Rey Aurelio (Asturias) Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Menéndez
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Pecharromán
authors.affiliation: Instituto Nacional del Carbón, INCAR-CSIC, Apartado 73, 33080 Oviedo, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Menéndez
authors.affiliation: Instituto Nacional del Carbón, INCAR-CSIC, Apartado 73, 33080 Oviedo, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Santamaría
keywords: Ceramic composites; Dielectric properties; Percolation threshold