(Ba_(1-x)Sr_x)(Mg_(1/3)Ta_(2/3))O_3微波陶瓷介电性能研究

STUDY ON DIELECTRIC PROPERTIES OF MICROWAVE CERAMIC (Ba_(1-x)Sr_x)(Mg_(1/3)Ta_(2/3))O_3

Ba(Mg1/3Ta2/3)O3(简称BMT)陶瓷是A(B′1/3B″2/3)O3(A=Ba,Sr;B′=Zn,Mg;B″=Nb,Ta)型复合钙钛矿化合物中的一种,A位由Sr离子取代Ba离子,形成(Ba1-xSrx)(Mg1/3Ta2/3)O3(简称BSMT)固溶体型化合物,也具有复合钙钛矿结构。Sr含量x≥0.6时发生相转变,形成一种新的低温相,这是由于氧八面体畸变造成的。这种低温相结构与BMT六方晶系结构相比具有较低的对称性。低温相的形成,可显著降低BSMT陶瓷的烧结温度,在1500℃即可烧结致密(BMT为1600℃)。BSMT的微观结构和介电性能(如介电常数ε和介电常数温度系数αε)的变化也与此相转变有关。

Ceramic Ba(Mg1/3Ta2/3)O3 (BMT) is known as one of the compound having the A(B1/3′B2/3″)O3 (A=Ba,Sr;B′=Zn, Mg; B″=Nb,Ta) complex perovskite structure. A solid-solution compound (BaSrx) (Mg1/3Ta2/3)O3 (BSMT) with complex perovskite structure was obtained by the substitution of Sr ions for Ba ions at the A-site. A new low-temperature phase caused by the tilting of oxygen octahedral are found as Sr content x≥0.6. This new low-temperature phase is clarified to have a lower symmetry than that of the hexagonal structure of BMT. The new low-temperature phase can decrease the sintering temperature of BSMT to 1500°C (1600°C for BMT). The microstructure and the dielectric properties of BSMT, such as the dielectric constant Ε and the temperature coefficient of dielectric constant αΕ, is related with the low-temperature phase transformation.