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Microwave Dielectric Properties of Sintered Alumina Using Nano‐Scaled Powders of α Alumina and TiO 2
Author(s) -
Huang ChengLiang,
Wang JunJie,
Huang ChiYuen
Publication year - 2007
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2007.01557.x
Subject(s) - materials science , sintering , microstructure , dielectric , ceramic , nano , dissipation factor , microwave , temperature coefficient , phase (matter) , analytical chemistry (journal) , composite material , mineralogy , chemistry , optoelectronics , physics , organic chemistry , chromatography , quantum mechanics
The microstructure and the microwave dielectric properties of nano‐scaled α alumina (α‐Al 2 O 3 ) ceramics with various added amounts of nano‐scaled TiO 2 have been investigated. The sintering temperature of nano‐scaled α alumina can be effectively lowered by increasing the TiO 2 content. The Q × f values of nano‐scaled α alumina could be tremendously boosted by adding an appropriate amount of TiO 2 . However, introducing excessive TiO 2 into the alumina ceramics would instead lead to a decrease in the Q × f values. The phases of TiO 2 and Al 2 TiO 5 co‐existed at 1350°C, and the maximum Q × f value appeared right after the eradication of TiO 2 phase at 1400°C. Consequently, increasing the TiO 2 content to 0.5 wt% yielded a Q × f value of 680 000 GHz (measured at 14 GHz) for nano‐scaled α alumina prepared at 1400°C for duration of 4 h. In addition, a very low loss tangent (tan δ) of 2 × 10 −5 was also obtained at 14 GHz. The τ f value is strongly correlated to the compositions and can be controlled through the existing phases. In fact, τ f could be adjusted to near zero by adding 8 wt% TiO 2 to α alumina ceramics. A dielectric constant (ɛ r ) of 10.81, a high Q × f value of 338 000 GHz (measured at 14 GHz), and a temperature coefficient of resonant frequency (τ f ) of 1.3 ppm/°C were obtained for nano‐scaled α alumina with 8 wt% TiO 2 sintered at 1350°C for 4 h. Sintered ceramic samples were also characterized by X‐ray diffraction and scanning electron microscopy.