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Liquid‐phase sintering, microstructural evolution, and microwave dielectric properties of Li 2 Mg 3 SnO 6 –LiF ceramics
Author(s) -
Zuo Ruzhong,
Zhang Jian,
Song Jie,
Xu Yudong
Publication year - 2018
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/jace.15257
Subject(s) - sintering , materials science , ceramic , microstructure , transgranular fracture , grain boundary , phase (matter) , analytical chemistry (journal) , dielectric , mineralogy , grain size , composite material , intergranular fracture , metallurgy , chemistry , organic chemistry , optoelectronics , chromatography
The liquid‐phase sintering behavior and microstructural evolution of x wt% LiF aided Li 2 Mg 3 SnO 6 ceramics ( x = 1‐7) were investigated for the purpose to prepare dense phase‐pure ceramic samples. The grain and pore morphology, density variation, and phase structures were especially correlated with the subsequent microwave dielectric properties. The experimental results demonstrate a typical liquid‐phase sintering in LiF–Li 2 Mg 3 SnO 6 ceramics, in which LiF proves to be an effective sintering aid for the Li 2 Mg 3 SnO 6 ceramic and obviously reduces its optimum sintering temperature from ~1200°C to ~850°C. The actual sample density and microstructure (grain and pores) strongly depended on both the amount of LiF additive and the sintering temperature. Higher sintering temperature tended to cause the formation of closed pores in Li 2 Mg 3 SnO 6 ‐ x wt% LiF ceramics owing to the increase in the migration ability of grain boundary. An obvious transition of fracture modes from transgranular to intergranular ones was observed approximately at x = 4. A single‐phase dense Li 2 Mg 3 SnO 6 ceramic could be obtained in the temperature range of 875°C‐1100°C, beyond which the secondary phase Li 4 MgSn 2 O 7 (<850°C) and Mg 2 SnO 4 (>1100°C) appeared. Excellent microwave dielectric properties of Q × f = 230 000‐330 000 GH z, ε r = ~10.5 and τ f = ~−40 ppm/°C were obtained for Li 2 Mg 3 SnO 6 ceramics with x = 2‐5 as sintered at ~1150°C. For LTCC applications, a desirable Q × f value of ~133 000 GH z could be achieved in samples with x = 3‐4 as sintered at 875°C.