Crystal structure, phase evolution and dielectric properties in the Li2ZnTi3O8-SrTiO3 system as temperature stable high-Q material

Abstract

In this paper, the crystal structure, phase evolution, microstructure and microwave dielectric properties were investigated in Li2Zn(1-x)Ti3O8-xSrTiO3 (x = 0–0.075) ceramic system well-sintered at 1075 °C for 4 h through one-step solid state reaction route. The XRD results showed that except for the main Li2ZnTi3O8 phase, the unknown phase started appearing at x = 0.01, and as x value was further increased to 0.025, the SrTiO3 phase appeared in sample and the relative content gradually increased. However, the slight deficiency of Zn2+ (x ≤ 0.025) could be used the decrease of molecular volume for Li2ZnTi3O8 crystal structure. Consequently, the relative permittivity (εr) and temperature coefficient of resonant frequency (τf) demonstrated a trend of fall first then rise as the cutoff point in x = 0.01, whereas the quality factor (Q × f) increased initially and then decreased. Typically, the Li2Zn0.95Ti3O8-0.05SrTiO3 ceramic showed a temperature stable high-Q material with εr = 26.6, Q × f = 62300 GHz, and τf = 0.27 ppm/°C. It could be found that the variation of Li2ZnTi3O8 crystal structure had an essential effect on dielectric properties of composite with ≤0.01, whereas that of composite with x ≥ 0.025 was determined by the relative content of Li2ZnTi3O8 and SrTiO3 phase. In addition, the unknown phase seemed to have no effect on dielectric properties.