Combined effect of rattling and compression on the microwave dielectric properties of B-site 1:3 ordered Li6A7Ti11O32 (A = Zn, Mg) spinels. Issue 6 (15th March 2023)

• Record Type: Journal Article
• Authors: Li, Mu; Tang, Ying; Xiang, Huaicheng; Li, Jie; Zhou, Di; Fang, Liang
• Is Part Of: Ceramics international. Volume 49:Issue 6(2023)
• Page Start: 8754
• Page End: 8761
• Publication Date: 2023-03-15
• Subjects: Rattling and compressed effects -- Spinel structure -- Cation ordering -- Microwave dielectric properties; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2022.11.021
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Dense ceramics of two B-site 1:3 ordering spinels Li6 A7 Ti11 O32 (A = Zn, Mg) with space group P 43 32 were prepared by solid-state reaction. Raman spectroscopy and XRD analysis revealed why the lattice parameters and volume of Li6 Mg7 Ti11 O32 are abnormally greater than those of Li6 Zn7 Ti11 O32 . Li6 Zn7 Ti11 O32 exhibits outstanding microwave dielectric properties ( Q × f = 129, 600 GHz (8.9 GHz), ε r = 20.7, τ f = −45 ppm/°C) and a low thermal expansion coefficient ( α L ) of 5.5 ppm/°C. While Mg-analogue displayed a lower Q × f ∼108, 600 GHz (9.1 GHz), a lower α L ∼ 4.9 ppm/°C, a higher ε r ∼ 21.9, and a slightly positive offset τ f ∼ −21 ppm/°C relative to Li6 Zn7 Ti11 O32 . A significant positive deviation of 91.6% was observed between the corrected ε r (corr) by the porosity and the calculated ε r (C-M) by the Clausius-Mosotti (C-M) equation in the Li1.33 x A2-2 x Ti1+0.67 x O4 solid solution. The variation in ε r and τ f values of Li6 A7 Ti11 O32 ( x = 0.5625) compared to Li2 ATi3 O8 ( x = 0.75) might be attributed to the combined effect of rattling and compression cations at A-site and B-site. Moreover, the negative τ f of Li6 A7 Ti11 O32 (A = Zn, Mg) ceramics was balanced to near zero by adding CaTiO3 .