Synthesis of Unusually High Valent Perovskite Oxide from the Highly Oxidized Coprecipitation Precursor - Takumi Nishikubo; Ryan J. Paull; Takatoshi Hirooka; Kana Matsuno; Koki Maebayashi; Jiong Ding; Hidetaka Kasai; Shigeo Mori; Takafumi Yamamoto; Kenneth R. Poeppelmeier; Masaki Azuma (Journal of the American Chemical Society, 2026)