Research Of Mg-Al-Ca-Si Based Ceramics

Miniaturization and high integration are the main development directions of current electronic products.In order to meet the development of electronic products,the requirements for the mechanical properties of LTCC substrate are higher and higher.How to prepare LTCC materials with high flexural strength at low sintering temperature has become a hot spot in the research of ceramic materials.Alumina is a ceramic material with excellent dielectric properties and high flexural strength,but the sintering temperature of alumina is very high,which cannot meet the requirements of LTCC technology.Therefore,the current mainstream method is to prepare the glass ceramics by compounding glass and alumina.The glass melts at a lower sintering temperature to form a liquid phase.The liquid phase glass is filled between the voids of alumina particles.Using this way,the alumina that should dense at high sintering temperature can dense at a lower sintering temperature.According to the different types of glass,the glass reacts with alumina to varying degrees,which improves the crystallinity of alumina glass ceramics,during the sintering process.It is helpful to further improve the flexural strength of glass ceramics.In this thesis,CaO-MgO-SiO₂ glass was prepared by high temperature melting and cold extraction.The prepared CaO-MgO-SiO₂ glass was mixed with alumina in different proportions to obtain Mg-Al-Ca-Si based glass ceramics by liquid phase sintering.On the basis of CaO-MgO-SiO₂ glass,Zn O and Ba O were added to prepare CaO-MgO-Zn O-SiO₂ glass and CaO-MgO-Ba O-SiO₂ glass respectively,and then the two glasses were compounded with alumina to prepare new glass ceramics.In this thesis,the sintering process,crystal phase composition,crystallinity,density,micro morphology,dielectric properties and flexural strength of glass ceramics prepared by compounding three kinds of glass and alumina in different proportions are tested and analyzed.CaO-MgO-SiO₂/Al₂O₃ glass ceramics made of CaO-MgO-SiO₂ glass and alumina belong to non-reactive liquid phase sintering.It has maximum flexural strength of 206 MPa,dielectric constant of 7.88,dielectric loss of 3.37×10^-3（12GHz）and the temperature coefficient of resonance frequency of-22 ppm/℃.CaO-MgO-Zn O-SiO₂/Al₂O₃ glass ceramics prepared from CaO-MgO-Zn O-SiO₂ glass and alumina belong to partial reactive liquid phase sintering.It has maximum flexural strength of 256 MPa,dielectric constant of 7.89,dielectric loss is 3.41×10^-3（12GHz）and the temperature coefficient of resonance frequency of-29 ppm/℃.CaO-MgO-Ba O-SiO₂/Al₂O₃ glass ceramics made of CaO-MgO-Ba O-SiO₂ glass and alumina belong to partial reactive liquid phase sintering.It has maximum flexural strength of 286 MPa,dielectric constant is 7.56,dielectric loss is 1.31×10^-3（10GHz）and temperature coefficient of resonance frequency of–27 ppm/℃.