Low Temperature Sintering CaO-Li₂O-La 2O₃-Nd₂O₃-TiO₂ Microwave Dielectric Ceramics

Low temperature co-fired ceramic (LTCC) technology, a remarkable interdiscip-linary integration of component technology, has become the preferred method of electronic components integrated, modular in the future in recent years. The core of LTCC technology is that how to synthesize microwave dielectric ceramics sintered with Ag, Cu, Ni and other electrode together. Microwave dielectric ceramics used currently have higher sintering temperature (>1300℃). The sintering temperature of microwave dielectric ceramics is reduced to below Ag or Cu melting point, which has become the future research directions. And as new electronic materials, microwave dielectric ceramics are widely used as the core microwave components in modern mobile communications, satellites broadcasting and radio-controlled fields, for example, in filters and resonators. In recent years, with the development of portable communication systems, the miniaturization of microwave devices is increasingly required. Multilayer co-fired ceramics (MLCC) is one of the solutions to satisfy this requirement. Multi co-firing requires that dielectric ceramics are co-fired with internal conductors such as Ag or Cu. Even though several types of dielectric materials with good microwave dielectric properties have been reported, most of them could only be well sintered at above 1300°C. Therefore, it is important to lower the sintering temperatures of microwave dielectric materials to less than the melting points of Ag or Cu without deteriorating the microwave dielectric properties.CaO–La₂O₃–Li2O–Nd₂O₃–TiO₂ (CLLNT) is composited by Ca0.6La0.8/3Ti3 and Li1/2Nd1/2TiO3 two kinds of opposite frequency-temperature coefficient, which has excellent dielectric properties;dielectric constantεr is 105, quality factor Q·f is 7000GHz, frequency-temperature coefficientÏ„f is 4.5ppm/℃. However, which has higher sintering temperature, and can't meet the Ag, Cu Co-firing. To reduce costs, generally use the method adding sintering aids to redue sintering temperature.ZnO-B₂O₃-SiO₂(ZBS)glass,ZnO-B₂O₃-La₂O₃ (ZBL)glass have low softening point which are used as sintering aids added in MgTiO3-CaTiO3, BaTi4O9, Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δand could significantly reduce the sintering temperature of these systems. However, the research of CLLNT low-temperature sintering has not been reported. Therefore, this article choose ZBS, ZBL, LiF as sintering adds and reduce the sintering temperature of CLLNT, while maintaining good dielectric properties and preliminary study of the incorporation of sintering additives on the sintering characterics, phase composition, microstructure, dielectric properties were investigated.1. ZBS glass , ZBL glass sintering aidsWe choosed ZnO, B₂O₃, SiO₂, La₂O₃ respectively to synthesize the ZBS, ZBL glass, and reduce the sintering temperature of CLLNT by adding appropriate amount glass from 1400℃to 1050℃. CLLNT doped glass has not changed the perovskite structure. CLLNT added 4wt%ZBS glass and sintered at 1050℃has excellent dielectric properties:εr= 76, tanδ= 0.0078,Ï„f = 8ppm/°C(4GHz);CLLNT added 15wt%ZBL glass and sintered at 1050℃has excellent dielectric properties:εr = 66, tanδ= 0.0078,Ï„f =–7ppm/°C(1MHz)。2. ZBS glass and LiF composite sintered aidsThe sintering temperature of CLLNT can only be droped to 1050℃,while the dielectric constant reduced to 76, 66 respectively. After adding 4wt%ZBS -1wt%LiF composite sintering aids , the sintering temperature of CLLNT ceramic could be reduced to 1000℃,and the CLLNT perovskite structure has not been changed. CLLNT added 4wt%ZBS-1wt%ZBL glass and sintered at 1000℃has excellent dielectric properties:εr=98,Q·f =1386GHz,Ï„f =42ppm /°C(4GHz).