Study On The Synthesis And Low Temperature Sintering Characteristics Of CaMoO₄ Ceramics

The scheelite-structured CaMoO₄ ceramic sintered at 1100? has excellent microwave dielectric properties,However,the high sintering temperature limits its application at low temperature co-fired ceramic?LTCC?technology.In this paper,the synthesis process of CaMoO₄ ceramics and the doping modification of CaMoO₄ ceramics were studied systematically,which made the CaMoO₄ ceramic materials meet the requirements of LTCC applications and also had good microwave dielectric properties.The main research works are as follows:The preparation process of CaMoO₄ ceramics was studied.The effects of sintering temperature on the micro-morphology and microwave properties of ceramics were discussed.The experimental results show that the proper calcining temperature can effectively eliminate the impurity phase in the synthesis process of CaMoO₄ ceramic.At the same time,good microwave dielectric properties were obtained by sintering at1150? for 5 h:e_r=9.64,Q×f=63996 GHz,?_f=-54.72 ppm/?.The sintering temperature of CaMoO₄ was reduced by adding low-melting sintering agents BaCu?B₂O₅?,LMZBS and LBSCA.The effects of doping amount on the morphology,density and microwave dielectric properties of ceramics were specially analyzed.According to the experimental results:?1?BaCu?B₂O₅?can effectively reduce the sintering temperature and have little effect on the microwave properties of ceramics.When the doping amount is 0.75 wt.%,the sintering temperature of ceramics is reduced to 875?.And the microwave performance reached the optimal value:e_r=10.67,Q×f=84775 GHz,?_f=-46.48 ppm/?.?2?Doping LMZBS can significantly reduce the densification temperature of ceramics,but it also causes the deterioration of microwave dielectric properties of materials.When the LMZBS doping amount is 0.5 wt.%,the sintering temperature of the ceramic is lowered to 875?,and the microwave performance can also reach optimal values:e_r=10.35,Q×f=67236 GHz,?_f=-53.02ppm/?.?3?Doping LBSCA can significantly reduce the densification temperature of ceramics,but it also led to a significant deterioration of the dielectric properties of materials.When the doping amount of LBSCA is 0.5 wt.%,the sintering temperature of the ceramic is lowered to 900?,and the microwave performance can also reach optimal values:e_r=10.81,Q×f=40034 GHz.Based on CaMoO₄+0.75 wt.%BaCu?B₂O₅?,the temperature coefficient of resonance frequency??_f?of ceramic materials was adjusted by compounding with positive temperature coefficient materials BaTiO₃ and CaTiO₃.At the same time,the effects of the addition of BaTiO₃ and CaTiO₃ on the phase composition,morphology and dielectric properties of CaMoO₄ ceramics were investigated.Experimental result shows:?1?BaTiO3can effectively adjust the?f value of CaMoO₄ ceramics.When the addition amount of BaTiO3 is 15 wt.%,the dielectric properties of ceramics for:e_r=14.23,Q×f=19524GHz,?_f=-4.41 ppm/?.?2?CaTiO₃ can effectively adjust the?_f value of CaMoO₄ceramics.When the addition amount of CaTiO₃ is 10 wt.%,the dielectric properties of ceramics are:e_r=14.92,Q×f=23034 GHz,?_f=2.03 ppm/?.