Microstructural and dielectric properties of ceramics based on K/sub 2/Sr/sub 4/Nb/sub 10/O/sub 30/ and BaTiO/sub 3/

Abstract

The search for dielectric materials with a high dielectric constant and /spl epsiv/ curves with a flat profile is still ongoing. K/sub 2/Sr/sub 4/Nb/sub 10/O/sub 30/-based dielectric ceramics, having the tetragonal tungsten bronze structure (TTB), which display a high permittivity and flat /spl epsiv/ curves meeting the X7R specification. BaTiO/sub 3/-based ferroelectric ceramics are classic dielectric materials for ceramic capacitors. Results were obtained by mixing compounds with closely related structures, such as the tetragonal tungsten bronze (TTB) niobate K/sub 2/Sr/sub 4/Nb/sub 10/O/sub 30/ (KSN) and the perovskite BaTiO/sub 3/ (BT). Phase compositions were analyzed by using XRD and the microstructure was investigated by SEM. The present study explores the dielectric curves /spl epsiv/ of the composition (K/sub 2/Sr/sub 4/Nb/sub 10/O/sub 30/)/sub x//spl middot/(BaTiO/sub 3/)/sub 1-x/ with x = 0.1-0.9 where x means the weight ratio of KSN. The dielectric constant at room temperature is lowest at x = 0.4. When x is between 0.4 and 0.7, /spl epsiv/ curves of the ceramic composites present a linear decrease with the temperature. Two different phases, TTB and perovskite type, are present after sintering.