CuO has been doped solely and together with BaO and SiO2 into barium titanate by mixing and calcination. X-ray diffraction showed that the sample doped by CuO-BaO has stable second hexagonal phase while the samples doped by CuO, CuO-SiO2 were of a pure perovskite phase. For CuO-BaO doping, the Curie temperature was decreased accompanied with higher εmax; while for CuO doping and CuO-SiO2 codoping, the Curie temperature was increased with εmax decreased. The difference can be explained considering that Cu2+ ion could not only incorporate into the BaTiO3 lattice, but also assemble in the boundary phase when CuO was doped solely. Besides, the mechanisms of CuO doping and SiO2 doping could happen at one time.
X-ray diffraction study of crystalline barium titanate ceramics