

However, a detailed investigation of the electronic-structure evolution during the topotactic phase transformation for understanding the underlying mechanism is highly desired.

Oxygen-vacancy-induced topotactic phase transformation between the ABO 2.5 brownmillerite structure and the ABO 3 perovskite structure attracts ever-increasing attention due to the perspective applications in catalysis, clean energy field, and memristors. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of ChinaĨ Collaborative Innovation Center of Light Manipulations and Applications, Shandong Normal University, Jinan 250358, People's Republic of China

1 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of ChinaĢ Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of Chinaģ Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of ChinaĤ Key Laboratory of Material Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, People's Republic of Chinaĥ Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of ChinaĦ Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
