| ?-Cordierite glass-ceramics has attracted much attention due to their excellent mechanical,dielectric and thermal properties,and was considered as the most potential low temperature co-fired ceramic?LTCC?substrate materials.In recent decades,the raw materials of?-cordierite glass-ceramics changed from the pure chemical reagent of expensive to the easy-gained and low-cost minerals/mine tailings.However,we need systematic experimental research because few studies on the modification of cordierite glass-ceramics doped with natural minerals or tailings doped with rare earth elements.Based on perlite tailings as main raw material,the effect of tailings amount on propertion of cordierite glass-ceramics was studied and the best content of perlite tailings was evaluated in this work.The effects of the sintering crystallization,phase and properties of cordierite glass-ceramics was doped with Gd2O3,Y2O3,Er2O3 and Sm2O3were investigated deeply,and the effects of the crystallization kinetics of?-cordierite glass-ceramics was doped with Gd2O3 and Y2O3 were discussed,and the relationship between the crystallization kinetics and properties of?-cordierite glass-ceramics was analyzed.Main research results are as follows:1.The increase in the amount of perlite tailings significantly reduces the Tg of the basic glasses,which is conducive to dense sintering.Tp1 has a slight decrease,and Tp2first increases and then decreases,which has a weak effect on the crystallization of?-cordierite,but has an inhibitory effect on the precipitation of?-cordierite.The density(2.58 g·cm-3)and the largest flexural strength?112 MPa?and the smallest dielectric constant?4.91,10MHz?of the glass-ceramics with the tailings dosage of 40 wt.%.At this time,the thermal expansion coefficient(2.35×10-66 k-1)matches the semiconductor material Si,and the dielectric loss is 0.021.2.It is conducive to the dense sintering of glass-ceramics was deped with Gd2O3,Y2O3,Er2O3 and Sm2O3;To promote the formation of?-cordierite and?-cordierite phases was deped with Gd2O3 and Y2O3.All the glass-ceramics were firstly precipitated in a continuous?-cordierite phase,the sintering temperature was increased or the sintering time was prolonged,and the transition from?-cordierite to?-cordierite phase was carried out until the whole?-cordierite phase was formed.The priority order of rare earth element doping to promote the precipitation of?-cordierite is:Gd2O3>Y2O3>Er2O3>Sm2O3.Compared with the unadulterated rare earth element MAS03,the order of influence of doping different rare earth elements on the density of glass-ceramics is Sm2O3>Gd2O3>Er2O3>Y2O3.The doping of Gd2O3,Y2O3 and Er2O3 in the perlite tailings can improve the fracture strength of a single?-cordierite glass-ceramics,and the content of 0.4 wt.%Sm2O3 can also improve its fracture strength.The order of influence of doping different rare earth elements on the fracture strength of glass-ceramics is Gd2O3>Y2O3>Er2O3>Sm2O3.3.The dielectric constants and dielectric losses?10 MHz?were 5.625.90 and0.0180.023?Gd2O3?,5.936.50 and 0.0190.021?Y2O3?,5.026.88 and 0.0210.025?Er2O3?,4.815.91 and 0.0150.019?Sm2O3?,respectively.Compared with MAS03,the doping of rare earth elements increases the dielectric constant of the glass-ceramics?except S02,4.81?,while the doping of Gd2O3,Y2O3 and Sm2O3 can significantly reduce the dielectric loss of glass-ceramics.The order of the dielectric loss optimization is:Sm2O3>Y2O3>Gd2O3>Er2O3.4.The thermal expansion coefficient of single?-cordierite glass-ceramics prepared by doping rare earth elements is smaller than or less than 3.53×10-6 k-1),and the dominant factors affecting the thermal expansion coefficient are crystallinity and porosity of crystal phase.The thermal expansion coefficients of glass-ceramics containing only?-cordierite doped with different rare earth elements were 1.563.53×10-6 k-1?Gd2O3?,2.352.93×10-6 k-1?Y2O3?,1.643.01×10-6 k-1?Er2O3?and 2.403.38×10-6 k-1?Sm2O3?,respectively.Compared with MAS03?900?-4h?,doping Y2O3,Er2O3 and Sm2O3 can significantly increase the thermal expansion coefficient of the glass-ceramics,and gradually get closer to the thermal expansion coefficient of semiconductor material Si,while doping Gd2O3 can significantly reduce the thermal expansion coefficient of glass-ceramics.5.The Kissinger equation and Ozawa equation were used to calculate the crystallization activation energy of?-cordierite doped with Gd2O3 and Y2O3 as399.06434.59 kJ/mol?K?,399.06434.59 kJ/mol?O?,3422.12498.46 kJ/mol?K?and352.90487.74 kJ/mol?O?,respectively.Moreover,the potential barrier formed by?-cordierite decreased first and then increased with the increase of the content of Gd2O3and increased first and then decreased with the increase of the content of Y2O3.It shows that Gd2O3 and Y2O3 doping can effectively promote the generation of?-cordierite,and Gd2O3 doping is better than Y2O3 doping,which is consistent with the above conclusions.The growth mode of?-cordierite changed from two-dimensional growth to one-dimensional growthwith the increase of Gd2O3 content,but the somatic nucleation remained unchanged.However,doping of Y2O3 does not affect the growth pattern of?-cordierite,which is both a somatic nucleation and a one-dimensional growth mechanism. |
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