lower than the Pr (15mC/cm2) in a previous study,20)probably due to the fact that the solid-state conventional mixed oxide method used in the previous study20) yielded two MPB compositions atx¼0:1and 0.5, which is different from the columbite-wolframite method used in this study,which showed only one MPB composition at approximately0:2x0:3. It is well known that ferroelectric values,such asPr,Ps, andEc, show maximum values approximatelyat the MPB composition