| In order to meet integration, miniaturization, modular, environmental protection for electronic components, Low temperature cofired ceramics (LTCC) for microwave application have become an attractive technology for the development of future electronic products in a high frequency application for resonator, filter, IC packaging radar, antennas and wireless.The effects of glass additives, TiO2doping and (Zn1/3Nb2/3)4+substitution on the sinterability, phase purity, microstructure, and dielectric properties of microwave ceramics based on Li2TiO3and Li2MTi3O8(M=Zn, Mg) has been investigated by using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy spectrum analysis (EDS) and Vector Network Analyzer. The results showed as the following:(1) The influence of LMB glass addition,(Zn1/3Nb2/3)4+substitute Ti4+on the sinterability, phase purity, microstructure, and dielectric properties of Li2TiO3microwave ceramics have been investigated. As for Li2Ti1-x(Zn1/3Nb2/3)xO3(0x0.5) ceramic, only monoclinic Li2TiO3was found in Li2Ti1-x(Zn1/3Nb2/3)xO3ceramics when x0.2. However, the monoclinic type of rock salt phase of Li2TiO3was transformed into cubic rock salt and a less amounts of Zn2Ti3O8phase was found when x0.3. The r and Q×f value firstly increased With increasing x when x=0.2, and then slightly decreased. The f value reduced from37.88ppm/℃to-26.73ppm/℃with increasing x. The addition of LMB glass in Li2TiO3ceramic can effectively lower the sintering temperature from1300℃to850℃Typically, the5wt%LMB glass-added Li2TiO3ceramic sintered at850℃/3h has better microwave dielectric properties of r=21.4, Q×f=64,122GHz, f=26.9ppm/℃.(2) Low-temperature firing and microwave dielectric properties of LBS glass-added ceramics with TiO2have been studied. The sintering temperature of ceramics can be reduced from1050℃to875℃by doping LBS glass additive. The r and Q×f value decreased with increasing LBS additive, and f decreases from-9.8to-13.4ppm/℃with glass fluxing. In order to make further improvement on dielectric properties, TiO2is selected to tune the temperature coefficient of resonant frequency (f) close to near zero, and increase the permittivity (r) and Q×f value. Typically, LZT+lwt%LBS+3.5wt%TiO2ceramic sintered at875℃/4h shows r=26, Q×f=44,023GHz, f=-4.4ppm/℃. Compatibility with Ag electrode indicates that this material may be applied to LTCC devices.(3) Silver co-firable Li2ZnTi3O8microwave dielectric ceramics with LZB glass additive and TiO2dopant have been investigated. The addition of LZB glass can effectively lower the sintering temperature to875℃, and does not induce much degradation of dielectric properties. The1.0wt%LZB glass-added ceramic has better properties of r=23.9, Q×f=31,608GHz,f=-14.3ppm/℃. Adding appropriate amount of TiO2can effectively adjust the temperature coefficient of resonant frequency (f) and improve permittivity (r). Typically, LZT+lwt%LZB+3wt%TiO2sintered at900℃/4h shows r=26.1, Q×f=45,168GHz, f=-4.1ppm/℃. Compatibility with Ag electrode indicates this material can be applied to LTCC devices.(4) The sinterability of LMB-added Li2MgTisO8ceramic have been studied. Adding LMB lowers sintering temperature from1025to875℃, and does not induce much degradation of dielectric properties. The r and Q×f value increase with the increas LMB glass content when the LMB additive reach to lwt%and then decreas. The1.0wt%LMB glass-added Li2MgTisO8ceramic sintered at875℃has better properties of r=26, Qxf=49,406GHz, f=3.2ppm/℃. Compatibility with Ag electrode indicates this material can be applied to low temperature cofired ceramic devices. |
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