Pseudo Phase Diagram and Microwave Dielectric Properties of Li₂O–MgO–TiO₂ Ternary System

Abstract

Li2O–MgO–TiO2 ternary system is an important microwave dielectric ceramic material with excellent properties and prospect in both scientific research and application. A phase diagram of the Li2O–MgO–TiO2 ternary system was established in this article, based on earlier research results and our present work. Microwave dielectric properties with compositions in different regions of the phase diagram have been analyzed. We found that the 0.33 Li2MgTi3O8–0.67 Li2TiO3 ceramics sintered at 1200°C exhibited excellent dielectric properties: Q × f value = 80 476 GHz (at 7.681 GHz), εr = 24.7, τf = +3.2 ppm/°C. We also designed two ceramic systems in the Li‐rich region of the Li2O–MgO–TiO2 ternary system, which received little attention in the past decades, because many excellent single‐phase ceramics, such as Li2MgTiO4, Li2MgTi3O8 and MgTiO3, have been found in the Ti‐rich region. The ceramic systems have low sintering temperatures but also relatively poor dielectric properties.

High Quality Factor, Ultralow Sintering Temperature Li6B4O9 Microwave Dielectric Ceramics with Ultralow Density for Antenna Substrates

“…Microwave dielectric losses include intrinsic and extrinsic parts. [40][41][42] with the former determined by its crystal structure and representing the upper limit of Qf. The latter is caused by defects and can be minimized by optimal processing.…”

Novel water-assisting low firing MoO3 microwave dielectric ceramics

“…Low temperature co-fired ceramic (LTCC) technology has become an important fabrication method for modern electronic devices due the low cost of manufacture and potential of the integration multiple microwave (MW) circuits. [1][2][3][4] LTCCs are required to have lower sintering temperatures than that of the inner metal electrodes (typically Ag, 961 o C) 5,6 but classic MW dielectric ceramics typically densify at > 1000 o C. [1][2][3][4][5][6][7] Lowering the sintering temperature of a MW ceramic by the addition of low-melting-point glasses and oxides has been used to fabricate many commercial LTCCs. [1][2][3][4][5][6][7] The search for intrinsically low sintering temperature LTCC has accelerated in recent years and the so-called family of ultra-LTCC (ULTCC) compounds can be well sintered at as low as 400 o C. [8][9][10][11] Most MW dielectric ceramics are oxides and their sintering temperatures are, to a simple approximation, determined by their melting points.…”

“…MoO3 powders are usually produced by roasting molybdenum disulfide in industry and take on a yellow color with a monoclinic crystal structure (space group Pbnm, a = 3.962 Å, b = 13.855 Å and c = 3.696Å). 15,16 Its theoretical density is 4.692 g/cm 3 with a melting point 795 o C and many MoO3-rich compounds have commensurately low melting points and sintering temperatures. However, when not alloyed with other binary compounds, MoO3 can be well densified.…”

Vibrational spectroscopic and crystal chemical analyses of double perovskite Y2MgTiO6 microwave dielectric ceramics

“…There is presently a strong ongoing exploration for materials with relative permittivity values of approximately 20 to meet various device demands. Researchers have developed solid solutions of the (Ca,Bi)(Mo,V)O 4 family, a ZnO–Nb 2 O 5 binary system, 0.25LiFe 5 O 8 –0.75Li 2 ZnTi 3 O 8 , 0.33Li 2 MgTi 3 O 8 –0.67Li 2 TiO 3 , NdNbO 4 –based structures, perovskite‐related structures and initially synthesized Bi 3 NbO 7 , BiSbO 4 , etc., ceramics with interesting properties. Among these materials, perovskite‐related structures have received considerable attention owing to their versatility and phase composition …”