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.