Structural Phase Transition and Microstructures in Stuffed Tridymite-Type Compounds; Ba(Al, Fe)₂O₄

Abstract

We have investigated structural phase transition and changes of microstrucrtures in BaAl₂O₄ with the tridymite tetrahedral framework structure by transmission electron microscopy experiments in the temperature range between 100 K and 298 K. In our polycrystalline samples the transition from the paraelectric phase with the P6₃22 space group to the ferroelectric (FE) phase took place around 250 K, which accompanies with the appearance of the modulated structure with the three equivalent modulation wave vectors, q = 1/2<100>. Real-space images revealed that the FE phase should consist of nanodomains with the 10 ∼ 20 nm size. In addition, it is revealed that partial substitution of Fe³⁺ for Al³⁺ in BaAl₂O₄ induced structural phase transition to the modulated structure with q = 1/3<110> around x ∼ 0.50 in Ba(Al_1-xFe_x)₂O₄.

Funding

Work at Osaka Prefecture University was supported by the Ministry of Education, Culture, Sports, Science, and Technology of Japan, (No. 25610076). Also, work at Nagoya University was supported by the Ministry of Education, Culture, Sports, Science, and Technology of Japan through a Grant-in-Aid for Young Scientists (B, No. 24760543).