1:2 cation order in A(Li1/3(Nb,Ta)2/3)O3 microwave perovskites

In a family of perovskites with the general stoichiometry (A(2/3)(2+)La(1/3))(B1/31+B2/35+)O-3, three 1:2 ordered perovskites were prepared with A=Sr, B1+=Li, B5+=Nb, Ta and with A=Ca, B1+=Li, B5+=Nb. These compounds can be sintered to high density at temperatures less than or equal to1350degreesC, have dielectric constants in the range 25-30, microwave quality factors as high as 26 000, and negative temperature coefficients of resonant frequency. A 1:2 polymorph was not observed for (Ca2/3La1/3)(Li1/3Ta2/3)O-3 which adopted a 1:1 ordered structure. The larger charge difference between the ions involved in the B-site ordering in these systems compared to other 1:2 ordered microwave perovskites such as Ba(Zn1/3Nb2/3)O-3, is reflected by a higher stability of the order which is stable up to their decomposition/melting temperature. (C) 2004 American Institute of Physics.