Effects of SrTiO 3 additives on the structure and microwave dielectric properties of Ba 4.2Sm 9.2Ti 18O 54 ceramics

Abstract

The effects of SrTiO 3 additives on the microstructure and the dielectric properties of Ba 4.2Sm 9.2Ti 18O 54 (BST) materials have been investigated. The microstructure of BST doped with SrTiO 3 was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA). The XRD, SEM and EPMA results showed that small amounts of SrTiO 3 (less than 4 wt.%) could be accommodated in BST while a secondary metatitanate phase appeared in the samples with 8 wt.% SrTiO 3 added, the addition of SrTiO 3 increased the lower solubility limit ( x values) of Ba 6−3 x Sm 8+2 x Ti 18O 54. The relative permittivities and the TC f values showed an approximately linear increase with increasing additions of SrTiO 3. It was observed that near zero TC f values could be achieved with the addition of SrTiO 3 to BST ceramics. With 4 wt.% SrTiO 3 addition and sintered at 1360 °C for 2 h, BST ceramics exhibited excellent dielectric properties: ɛ r = 81.2, Q f = 8470 GHz and TC f = −1.5 ppm/°C.