Effects of B₂O₃–Li₂O additions on the dielectric properties of screen printing Ba_0.6Sr_0.4TiO₃ thick films

Abstract

Ba_0.6Sr_0.4TiO₃ (BST) thick films were fabricated on Al₂O₃ substrate via the screen printing technology by using B₂O₃–Li₂O additions as liquid-phase sintering aids. The effects of doping of B₂O₃ and Li₂CO₃ on the phase compositions, microstructures, and dielectric tunable properties of the thick films were investigated systematically. The X-ray diffraction patterns showed that BST diffraction peaks shifted toward higher angle with the B₂O₃–Li₂O doping content, which indicated the substitution of B³⁺ and Li⁺ in Ba²⁺ site. It was also found that the grain size and electrical properties of the thick film were strongly affected by the glass content. The grain size and the relative permittivity decreased obviously with the increase of B₂O₃–Li₂O additive. In addition, for the thick film with 4.5 wt% glass content, optimized sintering, and electrical properties were obtained: the sintering temperature of 900 °C, relative permittivity of 312 (at 10 kHz), dielectric loss of 0.0039, tunability of 16.2% (at 3 kV/mm). These good sintering and electrical properties indicate that BST thick film with B₂O₃–Li₂O addition is benefit for the development of LTCC technology and tunable devices.