Resumen del trabajo presentado a la 14th International Conference of the European Ceramic Society, celebrada en Toledo (España) del 21 al 25 junio de 2015.Peer Reviewe

Blanco Rodríguez, Clara

Fernández-García, Lucía

Menéndez López, Rosa María

Menéndez, José Luis

Pecharromán, Carlos

Santamaría Ramírez, Ricardo

Digital.CSIC

High dielectric constant in Barium titanate-graphene composites around the percolation threshold L. Fernández-García1, J. L. Menéndez1, C. Pecharromán2, R. Menéndez3, R. Santamaría3 and C. Blanco3  1 Centro de Investigacion en Nanomateriales y Nanotecnologia, CINN-CSIC, Avenida de la Vega, 33940, El Entrego, Asturias, Spain. 2 Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, C/ Sor Juana Inés de la Cruz 3, 28049, Cantoblanco, Madrid, Spain. 3 Instituto Nacional del Carbón, INCAR-CSIC,  Apartado 73, 33080 Oviedo, Spain   Barium titanate is one of the most attractive ferroelectric materials with perovskite struture, which has been used as multi-layer ceramic capacitors (MLCC), ferroelectric random access memories (FRAM), piezoelectric sensors, optoelectronic devices, actuators, and so forth because of its excellent dielectric, piezoelectric and ferroelectric properties.   It is well known that the microstructure, dielectric and ferroelectric properties of barium titanate can be modified by introducing a wide variety of substitutions or dopants into their structure [1] or even by the addition of second phases to form composites materials [2], which leads to large changes in the mechanical [3], dielectric [4] properties.  In this work, we report the fabrication and dielectric properties of barium titanate-graphene composites with concentrations between 0 and 0.6% in weight of graphene. The samples were prepared using a simple processing route starting from barium titanate powders and an aqueous dispersion of graphene oxide, followed by spark plasma sintering at a pressure of 80 MPa, temperature of 1100 ºC and a holding time of 1 minute.  The introduction of graphene blocks grain growth and therefore, the final grain size decreases with graphene content. For this reason, the conductivity of the barium titanate-graphene composites does not monotonically increase with carbon content. This effect leads to two percolation thresholds (Figure 1) in which an increase of a factor of ten of the dielectric constant vs. pure barium titanate is obtained. In particular, Ɛ’≈ 35000 for the composite of 0.4% and Ɛ’≈ 13000 for the composite of 0.6% at a frequency of 10 kHz are obtained.  0.0 0.2 0.4 0.601x1042x1043x1044x104  10 kHzε'graphene (% weight)  Figure 1. Evolution of the real part of the dielectric constant of BaTiO3-graphene composites versus graphene weight concentration, at a frequency of 10 kHz.  [1] Cai W., Fu C., Lin Z., Deng X.: Vanadium doping effects on microstructure and dielectric properties of barium titanate ceramics. Ceramics International, 37, 3643-3650 (2011). [2] Pecharromán C., Esteban-Betegón F., Bartolomé J. F., López-Esteban S., Moya J. S.: New percolative BaTiO3-Ni composites with a high and frequency-independent dielectric constant (Ɛr≈80000). Advanced Materials, 13, 1541-1544 (2001). [3] Moya J.S., Lopez-Esteban S., Pecharromán C.: The challenge of ceramic/metal microcomposites and nanocomposites. Progress in Materials Science, 52, 1017-1090 (2007) [4] Fernandez-Garcia L., Suárez M., Menéndez J.L., Pecharromán C., Nuzhnyy D., Bovtun V., Savinov M., Kempa M., Petzelt J. Dielectric properties of carbon nanofibre/alumina nanocomposites. Carbon, 57, 380–387 (2013)  

High dielectric constant in Barium titanate-graphene composites around the percolation threshold

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