Combined effect of rattling and compression on the microwave dielectric properties of B-site 1:3 ordered Li6A7Ti11O32 (A = Zn, Mg) spinels

作者：Li, Mu; Tang, Ying^*; Xiang, Huaicheng; Li, Jie; Zhou, Di; Fang, Liang^*

来源：Ceramics International, 2023, 49(6): 8754-8761.

DOI：10.1016/j.ceramint.2022.11.021

• Rattling and compressed effects
• Spinel structure
• Cation ordering
• Microwave dielectric properties

Dense ceramics of two B-site 1:3 ordering spinels Li6A7Ti11O32 (A = Zn, Mg) with space group P4332 were prepared by solid-state reaction. Raman spectroscopy and XRD analysis revealed why the lattice parameters and volume of Li6Mg7Ti11O32 are abnormally greater than those of Li6Zn7Ti11O32. Li6Zn7Ti11O32 exhibits outstanding microwave dielectric properties (Q x f = 129,600 GHz (8.9 GHz), epsilon r = 20.7, tau f = -45 ppm/degrees C) and a low thermal expansion coefficient (alpha L) of 5.5 ppm/degrees C. While Mg-analogue displayed a lower Q x f -108,600 GHz (9.1 GHz), a lower alpha L - 4.9 ppm/degrees C, a higher epsilon r - 21.9, and a slightly positive offset tau f - -21 ppm/degrees C relative to Li6Zn7Ti11O32. A significant positive deviation of 91.6% was observed between the corrected epsilon r(corr) by the porosity and the calculated epsilon r(C-M) by the Clausius-Mosotti (C-M) equation in the Li1.33xA2-2xTi1+0.67xO4 solid solution. The variation in epsilon r and tau f values of Li6A7Ti11O32 (x = 0.5625) compared to Li2ATi3O8 (x = 0.75) might be attributed to the combined effect of rattling and compression cations at A-site and B-site. Moreover, the negative tau f of Li6A7Ti11O32 (A = Zn, Mg) ceramics was balanced to near zero by adding CaTiO3.

• 单位
  y; 西安交通大学; 桂林理工大学; 广西大学