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Microwave synthesis was optimized for preparing novel monoclinic Tin-doped barium niobate ceramics (Ba 1-x Sn x Nb 2 O 6 ; x = 0.0, 0.01, 0.05, 0.1, 0.2, 0.3) BSN. The intensity of monoclinic phase formation was observed to decrease on increasing tin as dopant indicating decreased crystallinity. Strained crystalline phase was observed in undoped sample that became severe on doping tin. Monoclinic metal alloy Sn 2 O 3 formation was confirmed on increasing tin doping beyond 5%. Electronic configuration of tin (II) oxide supports the local site-wise monoclinic disorder in crystal structure due to sterically active lone pair. Such a disorder arranges increased number of degenerate energy states and reduce effective energy gap between conduction band minimum and valence band maximum. All BSN compositions were investigated for monoclinic phase stabilization, ultra-violet absorption, dielectric response, raman modes and type of carrier concentration along with hall resistivity. All measurements possessed inflexion corresponding to 5% tin doping indicating successful site substitution and estimated Sn 2 O 3 metal formation beyond this. The values of reducing optical energy band gap, transparency to visible spectrum, hall resistivity and dc conductivity indicated utility of these materials as a target for growing transparent conducting oxide (TCO) films for substituting well-known indium tin oxide (ITO). • Microwave processing tailor flow of melt phases in Ba 1-x Sn x Nb 2 O 6 compositions to construct rare monoclinic structure. • Tin (p -block charge distribution) occupies more space in unit cell driving distortions in an interesting manner. • The evidence of SnO disproportion into SnO 2 and Sn 2 O 3 is confirmed through rise in direct current (dc) for 1% doped BSN. • An increase in covalence with tin doping is the source of alternative n-type and p-type semiconducting character of BSN. • Unstable Sn 2 O 3 phase is observed to stabilize due to quick cooling while withdrawing microwave power from 350oC to 25oC. [ABSTRACT FROM AUTHOR]