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High-performance dielectric thin film nanocomposites of barium titanate and cyanoethyl pullulan: controlling the barium titanate nanoparticle size using a sol–gel method

Suematsu, Koichi, Arimura, Masashi, Uchiyama, Naoyuki, Saita, Shingo, Makino, Teruhisa
RSC advances 2016 v.6 no.25 pp. 20807-20813
barium titanate, crystal structure, dielectric properties, electrical equipment, hydrolysis, nanocomposites, nanoparticles, particle size, pullulan, sol-gel processing, temperature
A monodispersed BaTiO₃ nanoparticle sol was prepared by a sol–gel method, and the sizes of the obtained nanoparticles were successfully controlled from 15 to 60 nm by controlling the amount of H₂O introduced for the hydrolysis reaction. Cyanoethyl pullulan (CEP) was added to the BaTiO₃ sol to prepare a nanocomposite ink of BaTiO₃ and CEP. A thin film was fabricated by spin-coating the ink on a Pt/Ti/SiO₂/Si wafer. The device obtained from the 30 nm BaTiO₃/CEP nanocomposite ink demonstrated the highest dielectric constant, about 50 at 1 kHz, during the particle size range from 15 to 60 nm. The temperature dependence of the dielectric constant at approximately 120 °C is eliminated using our BaTiO₃ nanoparticles, because of their cubic crystal structure, which does not show a transformation at 120 °C. These improvements of the dielectric properties are important for the development of thin film-type capacitors for compact electric devices.