Fabrication and dielectric properties of lead-free inorganic particles-epoxy resin composites

Inorganic-organic composites with a 0-3 connectivity are fabricated from inorganic particles with a high relative permittivity (epsilon(r)) and a low dielectric loss (tan delta), and epoxy resin. The compacted powder obtained by pulverizing BaZrO(3)-BaTiO(3)-Ba(Fe(1/2)Ta(1/2))O(3) (BZTFT) ceramics has 1/12th the epsilon(r), and 72 times the tan delta of the ceramics. On the basis of the relationship between epsilon(r) and BZTFT filler content, the experimental values of the composites are determined to be in good agreement with theoretical values calculated by following Nielsen's complex rule in the filler content range of 50-80 vol %. The temperature dependence of the dielectric properties of BZTFT powder/epoxy resins (90/10, v/v) composites measured at different frequencies suggests that the temperature characteristics of the present materials correspond to the Z8T characteristics [Z8T; Electronic Industries Association (EIA) standard: Delta C/C(25 degrees C) is expressed as a rate of change within +22 and -33% in the temperature range from 10 to 150 degrees C] when represented by the temperature characteristics of surface-mounted capacitors. It is shown that the effect of the vacuum drying of the filler on the dielectric properties of the composites is larger than that of the silane coupling treatment and that the dielectric properties can be improved synergistically by performing both treatments.