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Reseach of Properties and Microstructures for Al2O3-TiO2 Low Permittivity Microwave Dielectric Ceramics

Author: Ye
Tutor: LvWenZhong
School: Huazhong University of Science and Technology
Course: Materials Physics and Chemistry
Keywords: Al2O3-TiO2 Microwave dielectric ceramics Dielectric properties Doping Low dielectric constant
CLC: TQ174.1
Type: Master's thesis
Year: 2007
Downloads: 93
Quote: 2
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Abstract


Al 2 O 3 -TiO2 system is a system first study TiO2 content , adjust its the τf value to determine the best components ; then further study the different types of doping of the system to determine the sintering temperature , microstructure , and dielectric and mechanical properties . Are described below as follows : different content of TiO2 (τf = 450ppm / ℃), to compensate for the Al 2 O 3 negative τf value , so that (1-x) Al 2 O 3 < / sub > - xTiO2 material temperature coefficient of resonant frequency tends to zero , in order to determine the x value ; research calcining and sintering temperature on the dielectric properties of the system , to determine the most The optimum temperature . The study showed that: suitable calcining temperature of 1200 ℃, when x = 0.1 , ( 1- x ) Al 2 O 3 - xTiO2 materials by 1200 ℃ calcined 1550 ℃ after sintering , the τf value of approximately 1.5ppm / ℃. Nb 2 O 5 0.9Al 2 O 3 < / sub> - 0.1TiO2 ceramic structure and performance impact Nb5 and Al3 solid solution to the TiO2 to form a low temperature eutectic phase Ti0.8Al0.1Nb0.1O2, thereby reducing the sintering temperature , promote sintering . When the add 0.5wt% Nb 2 O 5 , the system of sintering temperature can be reduced to 150 ℃, the dielectric performance has improved significantly . 1200 ℃ calcined and sintered at 1400 ℃ , εr 10.38 , Qf 15500GHz τf value of about 9.6 ppm / ° C when the 0.9Al 2 O 3 < / sub > - 0.1TiO2 SiO2 additive when incorporated in a ceramic system , SiO2 and Al 2 O 3 reaction aluminosilicate glass phase, play the role of promoting sintering during the sintering process , thereby reducing sintering temperature ; SiO2 can be suppressed Al2TiO5 phase formation ; but of SiO2 introduced , will reduce the dielectric properties of the system . When the SiO2 content is 0.8 wt% , reduce the sintering temperature of the system to 100 ° C. and calcined at 1200 ℃ sintered at 1450 ° C , εr of 8.2, Qf to 9200GHz the τf of values ??of approximately -3.1 ppm / ℃ direct use of a low melting point Li3AlB2O6 (LAB) glass doped, to form a liquid phase to facilitate sintering at a high sintering temperature , thereby reducing the sintering temperature . The study showed that: adding a 1 wt% LAB glass can reduce the sintering temperature of the system 100 ℃; but will accelerate the TiO2 to the surface due to the introduction of the glass phase , overflow , causing the ceramic structural inhomogeneities ; calcined at 1200 ℃ , 1450 ℃ after sintering , εr 10.3, the Qf of as 14500GHz , the τf of value of about 15.6 ppm / ℃

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