The effects of Mg/sup 2+/ ions on the microwave dielectric properties of BaO-(Nd/sub 1-x/Bi/sub x/)/sub 2/O/sub 3/-4.5TiO/sub 2/ ceramics

Microwave dielectric properties of BaO-(Nd/sub 1-x/Bi/sub x/)/sub 2/O/sub 3/-4.5TiO/sub 2/ (x=0/spl sim/0.15), hereafter abbreviated as BNBT, ceramics modified with MgO or MgTiO/sub 3/ have been investigated to obtain low /spl tau//sub f/ materials suited for microwave applications. BNBT ceramics without Mg/sup 2+/ ions showed the dielectric constant of 92 and /spl tau//sub f/ of 12/spl sim/24 ppm//spl deg/C. The addition of MgO into BNBT ceramics up to 0.4 wt.% resulted in a. decrease in the dielectric constant without significant effects on the /spl tau//sub f/. In contrast, the addition of MgTiO/sub 3/ into BNBT ceramics reduced the /spl tau//sub f/ with an increased dielectric constant. As a result, we obtained BNBT ceramics with /spl epsiv//sub r/=94, Q/spl times/f/sub 0/=5, 130 GHz, and /spl tau//sub f/=0.2 ppm//spl deg/C, which are promising for commercial applications.