Abnormal phase transition and polarization mismatch phenomena in BaTiO_(3)-based relaxor ferroelectrics

Relaxor ferroelectrics have been extensively studied due to their outstanding dielectric,piezoelectric,energy storage,and electro-optical properties.Although various theories were proposed to elaborate on the relaxation phenomena,polar nanoregions formed by disruption of the long-range-order structures are considered to play a key role in relaxor ferroelectrics.Generally,relaxor ferro-electrics are formed by aliovalent substitution or isovalent substitution in normal ferroelectrics,or further combinations of solid solutions.Herein,one category of BaTiO_(3)-based relaxor ferroelectrics with abnormal phase transition and polarization mismatch phenomena is focused.Characteristic parameters of such BaTiO_(3)-based relaxor ferroelectrics,including the Curie temperature,polarization,and lattice parameter,show a typical“U”-shaped variation with compositions.The studied BaTiO_(3)-based relaxor ferroelectrics are mostly solid solutions of A-site coupling and B-site coupling ferroelectrics,exhibiting polarization mismatch in certain compositions[e.g.,0.9BaTiO_(3)-0.1BiScO_(3),0.8BaTiO_(3)-0.2Bi(Mg_(1/2)Ti_(1/2)O_(3),0.8BaTiO_(3)-0.2Bi(Mg_(2/3)Nb_(1/3)O_(3),0.5BaTiO_(3)-0.5Pb(Mg_(1/3)Nb_(2/3)O_(3),0.4BaTiO_(3)-0.6Pb(Zn_(1/3)Nb_(2/3)O_(30,etc.].Of particular interest is that excellent electrical properties can be achieved in the studied relaxor ferroelectrics.Therefore,polarization mismatch theory can also provide guidance for the design of new high-performance lead-free relaxor ferroelectrics.