Study On Low Temperature Sintering And Properties Of CaSiO₃-based Microwave Dielectric Ceramics

As information technology advances,communication products strive for reduced power consumption,increased speed and integration.As a new type of electronic ceramic material widely used in the electronic communication industry,microwave dielectric ceramics must have a low dielectric constant and a high Q×f value to achieve low delay and low loss of the circuit.Moreover,low-temperature co-fired ceramic technology as one of the important technical means to address the miniaturization and integration of communications equipment requires microwave ceramic materials have a low enough sintering temperature to co-fire with electrodes such as Ag and Cu.Researchers have been greatly concerned with the investigation of ceramic materials with low sintering temperature and remarkable microwave dielectric properties.CaSiO3 ceramics as one of the main crystalline phases of A6 materials(Ferro Corp.)inherently have the advantages of low dielectric constant and low dielectric loss.However,the sintering temperature is much higher than that required by low temperature cofired ceramic technology and the sintering temperature range is relatively narrow,making it difficult to sinter densely when prepared using conventional solid phase methods.In this thesis,the sintering temperature of CaSiO3 ceramics was reduced by incorporating appropriate amount of sintering additives for the purpose of sintering at the lowest possible temperature,and the microwave dielectric characteristics and low-temperature sintering process of the reduced sintered CaSiO3 ceramic samples were explored in this thesis.In this thesis,LBS glass and LBCB glass were prepared and LiF was selected as a sintering aid.All three sintering aids had good wettability with CaSiO3 ceramics.The XRD patterns showed that the addition of the three burners did not change the crystal structure of the CaSiO3 ceramics,and the samples were pure β-CaSiO3 phase;the SEM patterns showed that the appropriate amount of burners could promote the growth of the grains;the relative density and εr values,and the results of DSC and image sintering tests showed that the melting points of the three sintering aids were below 900℃,and the melting points of the two glasses reached below 800℃,it can be inferred that the relative density is the main factor affecting the reduced sintering CaSiO3 ceramic samples εr values;combined with the results of the thermal expansion analyzer and the sintering kinetics analysis,it can be seen that the sintering aids can promote the sintering densification process of CaSiO3 ceramics,thus reducing their sintering temperatures.The experimental results show that the CaSiO3-1.5wt.%LBS ceramic samples sintered at 1100℃ with εr=6.02,Q×f=45942GHz,τf=-22.66ppm/℃;microwave dielectric properties of ceramic samples at 925℃ when LiF doping is 1wt.%:εr=6.3,Q×f=32435GHz,τf=-28.51ppm/℃;at 950℃,CaSiO3-5wt.%LCBC ceramic samples possess the most remaekable microwave dielectric characteristics:εr=6.58,Q×f=35086GHz,τf=-33.56ppm/℃.In addition both CaSiO3-lwt.%LiF and CaSiO35wt.%LCBC ceramic samples have good chemical compatibility with silver.Finally microstrip antennas with center frequency of 2.51 GHz and bandwidth of 50 MHz and good radiation performance(gain up to 3.35 dBi)and high radiation efficiency(92.04%)were prepared based on CaSiO3-5wt.%LCBC microwave dielectric material.