NEW HIGH DIELECTRIC-CONSTANT MATERIALS - MICRO NANOCOMPOSITES OF SUSPENDED AU CLUSTERS IN SIO2/SI-2-AL2O3-LI2O GELS AND RELEVANT THEORY FORHIGH CAPACITANCE APPLICATIONS/

We have materials-designed, synthesized, processed, tested, and interp reted a micro/nanocomposite material consisting of a suspension of gol d clusters in an insulating matrix, aimed at producing a high-dielectr ic constant (> 200) high-breakdown-voltage capacitor. The resulting su spension utilizes SiO2 or a reacted form of SiO2-Al2O3-Li2O as the ins ulating matrix, and wasprepared by the sol-gel technique. The scientif ic approach employs the percolation theory expectation that at a criti cal topology of small metal elongated clusters amidst a ceramic or oth er insulating matrix, the dielectric constant of the resulting materia ls will reach a peak value as a function of spatial geometric loci. Ou r theoretical work indicates that the metal clusters should be optimal ly of atomic dimensions and approximately 100-300 A apart. The metal i slands must be ellipsoidal-like (or elongated globules or flocculates) to establish a dipole moment (that will be summed over the sample vol ume). High resolution microscope studies reveal that the gold clusters are observed to take on the general shape of truncated octahedra, whi ch indeed are appropriate for having a polarization vector (charge sep aration) due to an impressed electric field. From electron spectroscop y chemical analysis there exists indication that some of the clusters appear to be in a charged state. Dielectric constant measurements from 1 to 10 kHz have shown an average dielectric constant of 5000 in the Au-SiO2 gel sample over a wide temperature range of -100 to +100 degre es C, and a dielectric constant of 364-986 (with consideration for por osity) in the Au-SiO2/Al2O3/Li2O produced from Eucryptite (LiAlSiO4).