Phase formation, microstructure and microwave dielectric properties of Li2SnO3-MO (M=Mg, Zn,) ceramics

Abstract

Phase formation, microstructure and microwave dielectric properties of (1-x)Li2SnO3-xMO (M=Mg, Zn) ceramics have been investigated using x-ray powder diffractometer (XRD), scanning electron microscope (SEM) and a network analyzer at the frequency of about 8-12GHz in this paper. The results showed that Li2SnO3 formed limited range of solid solution ((β-Li2SnO3(ss)) with MgO doping (x ≤ 0.1) or ZnO doping (x ≤ 0.3). Multiphase of Li4MgSn2O7, β-Li2SnO3 (ss) and α-Li2SnO3(ss) existed in the compositions of x = 0.2−0.5 for MgO-added specimens. ZnO second phase appeared when x > 0.3 for the ZnO–added specimens. Dense and homogeneous microstructure could be obtained for the ZnO-doped composition with x = 0.3. The dielectric permittivity decreased with the increase of MgO doping content, but increased with the increase of ZnO dopant within the miscible compositional range (β-Li2SnO3(ss)). The presence of Li4MgSn2O7 or ZnO second phase reduced the dielectric permittivity. The doping of ZnO improved the Q × f value of β-Li2SnO3(ss), whereas the doping of MgO slightly decreased the Q × f value. The improvement of Q × f value could be ascribed to the stabilization of the ordering-induced domain boundaries by the partial segregation of the larger doping cation. The τ f value changed from positive into negative value with increasing MgO or ZnO addition and near zero τ f value (4.67 or −0.27 ppm/°C) could be obtained at x = 0.3 composition for MgO or ZnO added specimens, respectively.