Novel microwave dielectric LTCCs based upon V2O5 doped M2+Cu2Nb2O8 compounds (M2+ = Zn, Co, Ni, Mg and Ca)

The copper-niobates, M2+ CU2Nb2O8 (M2+ = Zn, Co, Ni, Mg or Ca) have good microwave dielectric properties when sintered between 985-1010 degrees C and 1110 degrees C for CaCU2Nb2O8. Therefore, they would be potential dielectric LTCC materials if they could be made to sinter below 960 degrees C (melting point of silver). To this end, additions of 3 wt.% V2O5 were made to ZnCu2Nb2O8, CoCu2Nb2O8, NiCu2Nb2O8, MgCu2Nb2O8 and CaCu2Nb2O8, and their sintering and dielectric behaviour was investigated for samples fired between 800 and 950 degrees C. Doping lowered sintering temperatures to below the 960 degrees C limit in all cases. Doping had the general effect of reducing epsilon(r), density, Qf and tau(f), although doped CaCU2Nb2O8 had a Qf value of 9300 GHz, nearly four times that of the best undoped sample. Doped ZnCu2Nb2O8 fired to 935 degrees C had Qf = 10,200GHz, and for doped CoCu2Nb2O8 fired to 885 degrees C Qf= 7500 GHz. When doped and undoped samples all fired to 935 degrees C were compared, all doped samples had greater 8, and density, and all except ZnCu2Nb2O8 had a smaller tau(f). All doped samples had a more linear relationship between frequency and temperature in the range 250-300 K. (c) 2005 Elsevier Ltd. All rights reserved.