Secondary phases could not be detected by XRD analysis due to the addition of 2.5 wt % of NiO.It assumed that the NiO addition in the grain boundary regions suppresses the grain growth during the sintering process, ensuing in a reduced densification of ceramic samples.With a further increase in the NiO content, εr swings in the same range.with addition of NiO the double peaks merged due to induced lattice strain. Increasing the NiO content gradually leads to a smaller lattice volume as showed by the XRD peaks shifting close to the higher angles.