Fabrication of Microwave Dielectric Ceramic Materials Mg2TiO4 and Mg4Ta2O9 for High-Frequency Wireless Communications

Abstract

A dual-substitution technique was used to modify the microwave properties of Mg2TiO4 and Mg4Ta2O9 materials Zn Ni Mn or Co ions would replace some of the Mg ions at the A sites and Nb ions replace Ta ions or Sn ions replace Ti ions at the B sites By using the analyses of XRD SEM and EDS the experiments showed that the properties of dual substitution for Mg4Ta2O9 were not better than those of single substitution for Mg4Ta2O9 such as (Mg1-xCox)4Ta 2O9 or (Mg1-xNix)4Ta2O9 On the other hand dual substitution for Mg2TiO4 could increase the quality factors effectively The experimental results showed that the present best microwave properties were ε_r~ 14 63 Q×f = 392 000 GHz (at 11 42 GHz) and τ_f ~ ?48 26 ppm/℃ for (Mg0 95Ni0 05)2(Ti0 95Sn0 05)O4 sintered at 1325℃ for 4h (Ca0 8Sr0 2)TiO3 was further used to compensate the negative value of τ_f The result showed that the microwave properties of ε_r~ 18 14 Q×f ~ 162 000 GHz and τ_f ~ +1 68 ppm/℃could be obtained for 0 93(Mg0 95Ni0 05)2(Ti0 95Sn0 05)O4?0 07(Ca0 8Sr0 2)TiO3 sintered at 1300℃for 4h The present work demonstrated that the dual substitution technique could be used to improve the microwave properties of Mg2TiO4 materials which are good candidates as the dielectric materials for microwave communications A compact microstrip square open-loop resonators for electric coupling planar microwave filters with 0? feed structure was investigated in this section Its size can be reduced by using a high permittivity ceramic substrate The selectivity and stop-band rejection of the designed filters can be significantly improved by utilizing a skew-symmetric (zero degree) feed structure The responses of the compact hairpin filters using FR4 (ε_r= 4 4 Dielectric loss (tanδ)= 0 015) Al2O3 (ε_r=9 8 Dielectric loss (tanδ) = 0 0002) 0 93(Mg0 95Ni0 05)2(Ti0 95Sn0 05)-0 07(Ca0 8Sr0 2)TiO3 (ε_r=9 8 Dielectric loss (tanδ) = 6 29×10-5) and 0 3(Mg0 95Ni0 05)4Ta2O9-0 7(Ca0 8Sr0 2)TiO3 ceramics (ε_r = 29 36 Dielectric loss (tanδ) = 3 375×10-5) ceramic substrates were designed to produce a center frequency of 2 4 GHz The compact size low-loss sharp response and performance of the filter are presented in this study

Date of Award	2019
Original language	English
Supervisor	Bing-Jing Li (Supervisor)