CaZn1/3Nb2/3O3-based dielectric ceramics for silver co-sintering applications
Résumé
The Ca(Zn1/3Nb2/3)O3 (CZN) complex perovskite oxide has been studied for its attractive dielectric properties (εr=34, Qxf=15 890GHz, τf=-48 ppm.°C-1) for applications such as multilayer ceramics capacitors or hyperfrequency resonators. Nevertheless, high temperatures (>1250°C) are required to obtain well dense CZN ceramic, prohibiting any silver co-sintering (Tf (Ag) = 961°C). For that reason, the sintering temperature lowering of CZN by glass phase’s additions has been investigated. This material is finally sinterable at low temperature with combined glass phase -lithium salt additions, and exhibits, at 1MHz, very low dielectric losses, a relatively high dielectric constant with a good stability versus temperature. The 2%weight of ZnO-SiO2-B2O3 glass phase and 1%wt of LiF added CZN sample sintered at 920°C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant εr of 22, low dielectrics losses (tan (δ)< 10-3), a temperature coefficient of the permittivity τε<100 ppm.°C-1, and an insulating resistivity higher than 1013Ω.cm. Its interesting properties and its co-sinterability with silver electrodes make this ceramic suitable for L.T.C.C applications.