Research On Modification And Application Of Zn-Zr-Nb Microwave Dielectric Ceramics

Microwave dielectric ceramics are basic materials in the field of electronic information,and have a very wide range of applications in wireless communication,Internet of Things,smart medical and radar detection.In order to meet people’s needs,the urgent problem that needs to be solved is to promote the integration,high frequency and portability of electronic equipment.Low temperature co-fired ceramic（LTCC）technology has become the most popular passive integration technology due to its low cost,high integration and high compatibility.In this thesis,ZnZrNb₂O₈ ceramics with excellent properties are taken as the research object.Aiming at the shortcomings of high sintering temperature and poor temperature stability,the properties of ZnZrNb₂O₈ ceramics are controlled by methods such as ion replacement,doping of sintering aids and two-phase composite.The specific research work is as follows:（1）The composite ion（Sn1/2W1/2）5+with the same valence state is used to replace Nb5+.In the serialization experiment,it was found that the ceramic sample of ZnZrNb2x（Sn1/2W1/2）xO8 sintered at 1175℃ for 4 h has the highest density.The dielectric constant is mainly related to density and ionic polarizability,and its quality factor has a great correlation with density and the Raman Full Width at Half Maximum.Meanwhile,the introduction of（Sn1/2W1/2）5+deteriorates its temperature stability of ceramic samples.The microwave dielectric properties of ZnZrNb1.97（Sn1/2W1/2）0.03O8 synthesized at 1175℃ are:εr=27.956,Q ×f=57400 GHz,τf=-50.5 ppm/℃.（2）Aiming at the problem that the sintering temperature of ZnZrNb₂O₈ ceramics is too high to meet the co-firing with Ag in LTCC technology,the low-melting LBS and LMZBS glasses were used as sintering aids to conduct low-temperature sintering experiments respectively.Both of these glasses can reduce the sintering temperature of ZnZrNb₂O₈ ceramics from 1175℃ to 950℃,and also maintains excellent dielectric properties.The dielectric properties of ZnZrNb₂O₈-1.5 wt.%LBS ceramics sintered at 950℃ are:εr=26.67,Q ×f =36140 GHz,τf=-57.32 ppm℃.The dielectric properties of ZnZrNb₂O₈-2.0 wt.%LMZBS ceramics sintered at 950℃ are:εr=26.30,Q ×f=39729 GHz,τf=-52.44 ppm/℃.（3）Adding LBSCA glass and TiO2 with positive temperature coefficient to ZnZrNb₂O₈ ceramics,and makes ZnZrNb₂O₈ ceramics have excellent temperature stability while satisfying LTCC.The experimental results found that with the increase of TiO2,the τf value of the ceramic samples gradually shifted to the positive direction.The dielectric properties of the 0.25ZnZrNb₂O₈-0.75TiO2-1.2 wt.%LBSCA ceramic synthesized at 950℃ are:εr=34.978,Q ×f=20666 GHz,τf=5.05 ppm/℃.（4）A microstrip patch antenna with a center frequency of 2.4 GHz was designed and simulated based on ZnZrNb₂O₈-2.0 wt.%LMZBS ceramics and 0.25ZnZrNb₂O₈0.75TiO2-1.2 wt.%LBSCA composite ceramics.Its bandwidth is about 20 MHz,and the maximum gain exceeds 3 dB.The practicability of the materials prepared in this thesis is verified.