CHARACTERISATION AND MICROWAVE DIELECTRIC PROPERTIES OF M(2+)Nb2O6 CERAMICS

• Published in: Journal of the American Ceramic Society Vol. 88; no. 9; pp. 2466 - 2471
• Main Authors: Pullar, R C, Breeze, J D, Alford, N McN
• Format: Journal Article
• Language: English
• Published: 01.01.2005
• ISSN: 0002-7820
• DOI: 10.1111/j.1551-2916.2005.00458.x

The quality factor (Q), dielectric permittivity (epsilonr) and temperature coefficient of resonant frequency (tauf) of the TE01delta mode of the columbite binary niobate ceramics, with the formula MNb2O6 where M = 2+ cation, were investigated in relation to their degree of sintering, microstructure and phase composition. The ceramics were made from a mixed oxide preparative route and fired over a range of temperatures from 800 to 1400 C, and most formed the columbite structure. A comprehensive study was made of the niobates containing the transition metal cations M = Mn2+, Co2+, Ni2+, Cu2+, and Zn2+, and the group II metal cations M = Mg2+, Ca2+, Sr2+, and Ba2+. All columbite niobates had epsilonr between 17 and 22 and negative tauf values between -45 and -76 ppm /C, and ZnNb2O6, MgNb2O6, CaNb2O6, and CoNb2O6 had high Qf values of 84500, 79600, 49600, and 41700 GHz, respectively. The Qf of MgNb2O6 rose to over 95000 GHz when heated at 1300 C for 50 h. 25 refs.