Oxygen vacancies and their effects on tilting transition in perovskite (La_(1-x)Pr_x)_(1/3)Sr_(2/3)FeO_(3-δ) investigated by mechanical spectroscopy

摘要

We present the results of kilohertz mechanical spectrum of perovskite (La_(1-x)Pr_x)_(1/3)Sr_(2/3)FeO_(3-δ) (x = 0 to 1) samples. An oxygen vacancy related internal friction peak was observed around 400 K in oxygen nonstoichiometric La_(1/3)Sr_(2/3)FeO_(3-δ) and Pr_(1/3)Sr_(2/3)FeO_(3-δ) samples. An octahedral tilting Pm3m↔ R3c transition appeared as a step-like decrease of modulus with the decrease in temperature in less oxygen nonstoichiometric (La_(1-xPr_x)_(1/3)Sr_(2/3)FeO_(3-δ) samples. Another unsymmetrical internal friction peak due to the relaxation of domain walls was observed just below the tilting transition. The different behavior of oxygen vacancies and their complicate interaction with ferroelastic domains were suggested in various oxygen nonstoichiometric La_(1/3)Sr_(2/3)FeO(3-δ) and Pr_(1/3)Sr_(2/3)FeO_(3-δ) samples.