The correlation between the structure and the dielectric properties of KxBa1-xGa2-xGe2+xO8 ceramics

• Published in: Journal of the European Ceramic Society 2007, Vol.27 (8-9), p.2957-2961
• Main Authors: MARJETA MACEK KRZMANC, MEDEN, Anton, SUVOROV, Danilo
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Electrotechnical and electronic ceramics; Exact sciences and technology; Technical ceramics
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2006.11.021

A study of KxBa1-xGa2-xGe2+xO8 ceramics revealed that these solid solutions undergo a monoclinic-to-monoclinic P21/a-C2/m phase transition. The temperature of this phase transition decreased with increasing x, in a similar way to the sintering temperature, which decreased from 1100 C (x = 0) to 970 C (x = 1). The temperature of the P21/a-C2/m phase transition was below the sintering temperature of KxBa1-xGa2-xGe2+xO8 (x = 0.67-1) solid solutions, whereas the compositions at lower x (x = 0.4 and 0) remained in the P21/a modification over a wide temperature range above the sintering temperature. Compared to the C2/m modification of KxBa1-xGa2-xGe2+xO8 (x = 0.67-1), with a permittivity of 6.2-6.9, the P21/a modifications had permittivities of 5.9-7.0 and three-to-eight times higher Qxf values of about 100000 GHz (at about 12 GHz). The temperature coefficient of the resonant frequency was about -25 ppm/K, regardless of the composition. 9 refs.