Sintering Behavior and Microwave Dielectric Properties of MgTiO3 Ceramics Doped with B2O3 by Sol-Gel Method

The B2O3-doped MgTiO3 powders and ceramics have been prepared by sol-gel method using Mg(NO3)2·6H2O, Ti(C4H9O)4 and H3BO3 as the starting materials. The sintering behavior and microwave dielectric properties of ceramics prepared from powders with different particle sizes were investigated. The gels were calcined at 650, 700, 750, 800, 850 and 900 C and the derived particle sizes of powders were 20–30 nm, 30–40 nm, 40–60 nm, 60–90 nm, 90–120 nm and 120–150 nm, respectively. The nanoparticles with the size of 30–60 nm benefited the sintering process with high surface energy whereas nanoparticles with the size of 20–30 nm damaged the microwave dielectric properties due to the pores in the ceramics. The addition of B2O3 used as a liquid sintering aid reduced the sintering temperature of MgTiO3 ceramic, which was supposed to enter the MgTiO3 lattice and resulted in the formation of (MgTi)2(BO3)O phase. The B2O3-doped MgTiO3 ceramic sintered at 1100 C and prepared from the nanoparticles of 40–60 nm had compact structure and exhibited good microwave dielectric properties: εr=17.63, Q × f=33,768 GHz and τ f= 48×10 6 C 1.