Order-disorder phase formation in the complex perovskite compounds Ba(Ni1/3Nb2/3)O-3 and Ba(Zn1/3Nb2/3)O-3

The order-disorder phase formation of the complex perovskite compounds Ba(Ni1/3Nb2/3)O-3 (BNN) and Ba(Zn1/3Nb2/3)O-3 (BZN) was investigated using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The BNN and BZN samples were sintered over a temperature range of 1200 degrees to 1500 degrees C in air for 2 h. X-ray diffraction and transmission electron microscopy showed that these compounds exhibited a 1:2 ordering on the B-site within a narrow temperature range. When BNN and BZN mere sintered above 1400 degrees and 1350 degrees C, respectively, a liquid phase formed in the grain boundary which was accompanied by disordering, The composition of the liquid phase resembled that of pyrochlore, with a small amount of nickel for BNN or zinc for BZN, The disordering with the formation of the liquid phase was attributed to the increase in defect concentration.