Fabrication of high quality factor cold sintered MgTiO3–NaCl microwave ceramic composites

Abstract

Magnesium titanate is a well-known low loss dielectric ceramic, widely used in dielectric resonator and multilayer ceramic capacitor applications. But its high sintering temperature (1400°C) results in high energy consumption and thereby increases the environmental pollution and production cost. Furthermore, traditional sintering methods restrict co-sintering of ceramics with low melting metals and polymers. Cold Sintering Process (CSP) which provides a simple, effective and energy saving strategy for ceramic fabrication has not yet been reported for the fabrication of magnesium titanate based microwave dielectric ceramics. In the present work, dense samples of xMgTiO3-(1-x)NaCl (x = 0–0.5) ceramic composites were successfully prepared by cold sintering process (CSP) for the first time, at < 250°C, in 30 min,under a uniaxial pressure of 450 MPa. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) reveal that both MgTiO3 and NaCl co-exist in all the composites without any chemical reaction between the two phases. Raman spectra and scanning electron micrograph of MgTiO3 confirm the presence of MgTi2O5 as indicated by XRD. Relative permittivity (εr) of xMgTiO3- (1-x)NaCl composite increases and temperature coefficient of resonant frequency (TCF) decreases with increasing x; Qxf shows a non-linear variation with a maximum value of 29,500 GHz at x = 0.2. Results indicate that density, grain size and homogeneity of the particles influence the Qxf value of the composites. This study highlights the potential of cold sintering for the fabrication of MgTiO3 based composites with competitive microwave dielectric properties.