Microwave dielectric properties and crystal structures of spinel-structured MgAl₂O₄ ceramics synthesized by a molten-salt method

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• 作者：Susumu Takahashi ; Akinori Kan ; ^{akan@mejio-u.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Hirotaka Ogawa
• 关键词：Spinel ; Microwave dielectric ; Molten-salt method ; Cation distribution ; MgAl2O4
• 刊名：Journal of the European Ceramic Society
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：37
• 期：3
• 页码：1001-1006
• 全文大小：1126 K

文摘

The microwave dielectric properties and crystal structures of MgAl₂O₄ ceramics synthesized using either molten-salt (MA-M) or solid-state reaction (MA-S) methods were characterized in this study. Raman and ²⁷Al solid-state nuclear magnetic resonance spectra indicated that Al³⁺ cations primarily occupied in tetrahedral sites of the MA-M ceramic. The degree of inversion x, i.e., degree of cation disorder in tetrahedral and octahedral sites, of the MA-M was higher than that of MA-S; such the preferential site occupation of Al³⁺ cations enhanced the covalency of the MO bonds in the MO₄ tetrahedra (M = Mg and Al), leading to a decrease in the lattice parameters. The Q·f of the MA-M fired at 1600 °C was 201,690 GHz, while the MA-S synthesized at 1600 °C exhibited a Q·f of just 85,100 GHz. Based on these results, an intermediate spinel structure with a greater x evidently has a higher Q·f, and therefore the cation distribution is closely related to the Q·f of the ceramic.