“…[4][5][6] Pb(In 1/2 Nb 1/2 )O 3 ͑PIN͒ lies very close to the phase boundary between the ordered phase and the disordered one. 7,8 It has been reported that the disordered PIN having the 20-30 nm ordered regions 8 shows the relaxor behavior, 5,8,9 while the ordered PIN having the 80-100 nm ordered regions 8 is isostructural with antiferroelectric PbZrO 3 ͑PZ͒ at room temperature. 7,8 We have previously examined phase transitions and dielectric properties of (1 Ϫx)PINϪxPZ ͑abbreviated Zr-PIN͒ and (1Ϫx)PIN ϪxPb(In 1/2 Yb 1/2 )O 3 ͑PYN͒ ͑abbreviated Yb-PIN͒ systems and have found the morphotropic phase boundary between pseudocubic ͑relaxor͒ and rhombohedral ͑ferroelectric͒ phases around xϭ0.35 for Zr-PIN 10 and that between pseudocubic ͑relaxor͒ and orthorhombic ͑similar to that of antiferroelectric ordered PYN͒ phases around xϭ0.20 for Yb-PIN.…”