Identification of Barium Hydroxo-Hydroperoxostannate Precursor for Low-Temperature Formation of Perovskite Barium Stannate

A breakthrough “superoxide colloidal solution route” for low-temperature synthesis of barium and strontium stannate perovskites and their doped analogues was recently introduced. The synthesis starts from hydrogen peroxide-rich stannate solutions and yields a so-called “crystalline superoxide molecular cluster” that is converted by low temperature (<300 °C) to the respective perovskites. In this paper, the so-called “crystalline superoxide molecular cluster” is identified as a superoxide-free, barium trihydroxo­(hydroperoxo)­peroxostannate, BaSn­(OH)₃(OOH)­(OO) phase (BHHPS). EPR and Raman spectroscopy studies reveal the absence of superoxide in this crystalline phase. FTIR of the deuterated sample, ¹¹⁹Sn NMR, and elemental analysis uncovered the empirical formula, H₄O₇SnBa with two peroxides per each tin element. Rietveld refinement of the XRD confirms the BHHPS cubic phase with replacement of the perovskite oxygen atoms by the OH- and OOH-ligands and peroxobridging groups.