Effect of a BaO-CuO-Bi2O3-B2O3 glass flux, and its processing on the dielectric properties of BaTiO3

A series of BaTiO3 along with various flux oxides has been sintered step-wisely to yield a low sintering temperature flux glass composition. The developed glass flux (Ba-Cu-Bi-B system) was added to BaTiO3 with different amount, and eventually yielded a low sintering temperature of BaTiO3 at 900 °C with 7 wt% flux glass addition. To investigate the influence of processing methods, a flux glass shell-BaTiO3 core structure was developed by using separate ball milling schedule of glass and barium titanate powders. Comparison of resultant dielectric properties was made among different processing methods, and this flux shell processing methods notably modifies the dielectric properties of sintered samples comparing to conventional processing methods. The subsequent structural information, morphology, and phase stability of sintered samples were investigated by Infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. 93 wt% BaTiO3-7 wt% glass with the flux shell structure displayed an inhibited cubic phase grain growth, and a reduced tetragonality associated with Cu doping was confirmed by X-ray diffraction. A high dielectric constant (>3000) as well as a low lossy factor (<0.03) of this particular series of sample was reported. X-ray photoelectron spectroscopy showed that bridging oxygen species decreases with increasing Nd addition, indicating that the Nd bonds to the glass network as a network modifier instead of being doped into BaTiO3 lattice through the flux shell. Thus, we concluded that the glass flux shell plays the role of sintering additive, Cu doping ion (contained in glass) carrier, and Nd alien dopant block.