Effect of oxygen partial pressure on grain boundary structure and grain growth behavior in BaTiO3

Abstract The structural transition of grain boundaries in BaTiO 3 and related grain growth behaviors have been investigated for a wide range of oxygen partial pressures ( P O 2 ) . A correlation among P O 2 , grain boundary structure and grain growth behavior has been found. At P O 2 = 0.2 atm , all of the grain boundaries were faceted and abnormal grain growth occurred with the assistance of {1 1 1} twins as in previous investigations. As P O 2 decreased below 10 −11 atm the formation of {1 1 1} twins was inhibited. At a moderately low P O 2 between 10 −11 and 10 −17 atm, grain growth was suppressed, although a small fraction, less than 10%, of the boundary was rough. With an increased fraction of rough boundaries on reduction of P O 2 to 4 × 10 −18 atm, abnormal grain growth was observed for the first time in the absence of {1 1 1} twins in BaTiO 3 . Further increases in the rough fraction to ∼80% changed the growth behavior to normal. These observations show that in BaTiO 3 , a variety of growth behaviors can result with reduction of P O 2 : from abnormal with the assistance of {1 1 1} twins, stagnant without {1 1 1} twins, abnormal again without {1 1 1} twins to normal without {1 1 1} twins. The observed difference in growth behavior with P O 2 and grain boundary structure has been explained in terms of the change in step free energy and the critical driving force for appreciable migration of the boundary.