Dense LiF microwave dielectric ceramics with near-zero linear shrinkage during sintering

Abstract

In order to improve the densification of LiF ceramics, LiF green compacts were prepared by room-temperature cold sintering through uniaxially pressing the mixture of LiF powder and water. With increasing the compacting pressure from 100 to 800 MPa, the relative density of mechanically robust LiF compacts increased dramatically from 69.4% to 92.4%, which was attributed to the plastic deformation and dissolution-precipitation mechanism with the aid of high pressure and water. The relative density and microstructural homogeneity could be further improved by sintering the compacts at 825 °C, and the highest relative density of 95.4% was obtained in LiF ceramic with the compacting pressure of 800 MPa, which also exhibited the optimum microwave dielectric properties of εr = 8.53, Qf = 118,400 GHz and τf = −154 ppm/°C. Moreover, the linear shrinkage of LiF ceramics during sintering could be significantly reduced by increasing the compacting pressure and relative density of the green compacts, and it was as low as 1.1% for the compacting pressure of 800 MPa.