Tin(II) Oxide
Properties
| State | Solid |
| Color | Blue-black (stable form) or red (metastable form) |
| Solubility | Insoluble in water; soluble in acids and alkalis (amphoteric) |
| Melting Point | 1080 °C (decomposes - disproportionates to Sn + SnO2) |
About Tin(II) Oxide
Tin(II) oxide is the dark, layered, lone-pair-bearing cousin of cassiterite — and it's a textbook example of how a stereochemically active 5s2 lone pair distorts coordination geometry in a heavy main-group element. SnO crystallizes in the litharge structure (the same one PbO adopts), with each Sn atom sitting at the apex of a square pyramid of four oxygens and the two 5s electrons projecting into the empty sixth site. That asymmetry pushes the layers apart and turns what would otherwise be a plain rocksalt-type oxide into a 2D material with a 2.7 eV indirect bandgap. SnO is metastable: heat it above 300 °C in air and it disproportionates to elemental Sn plus the more stable SnO2 (cassiterite), which is why bottled SnO has to be kept dry and kept cool. The current research story is p-type transparent electronics — most transparent conducting oxides like ITO and FTO are n-type, and the field has spent two decades looking for a p-type partner with hole mobility above 100 cm2/V·s for transparent CMOS. SnO thin films deposited by atomic layer deposition or pulsed laser deposition routinely hit 200 cm2/V·s, putting them ahead of CuAlO2 and Cr2O3 alternatives. Beyond electronics, SnO sees use as a precursor to organotin chemistry, a mild reductant in inorganic synthesis, and an anode material in next-gen lithium-ion battery research with a theoretical capacity of 875 mAh/g via the Sn-Li conversion-then-alloying mechanism.
Where you'll encounter it
If you've ever read a paper on flexible transparent displays or peered into the literature on p-type oxide TFTs for the next generation of foldable phones, you've seen SnO thin films described as the most credible p-type partner for ITO. Samsung and LG both have SnO research lines because the holy grail of flexible display electronics is a transparent CMOS inverter — you need both n-type and p-type oxide semiconductors deposited on the same flexible substrate, and SnO is the only credible p-type candidate that survives the ALD temperature window. In a battery research lab, SnO powder ground with carbon black and PVDF binder, cast onto copper foil, and assembled into a 2032 coin cell will show two discharge plateaus on the first cycle — the conversion to Sn0 plus Li2O around 0.9 V, then Li-Sn alloying down to 0.05 V — exactly the textbook cyclic voltammogram the conversion-alloying mechanism predicts.
Common Uses
- P-type transparent semiconductor in flexible display thin-film transistor research
- Anode material in lithium-ion and sodium-ion battery research at 875 mAh/g theoretical capacity
- Precursor to organotin chemistry and Sn(II) coordination complexes for catalysis
- Mild reductant in specialty inorganic and organic synthesis at moderate temperatures
- Historical blue-tint colorant in lead-free crystal glass and ceramic glazes
Safety Information
GHS: not classified as a health hazard in most jurisdictions because inorganic tin has low oral and dermal toxicity. Inorganic tin compounds carry a low occupational dust limit expressed as Sn. Bulk powder generates respirable dust during weighing and ball-milling — wear an N95 respirator and weigh in a fume hood or laminar flow bench. SnO disproportionates exothermically above 300 °C in air, so calcining stannous oxide at high temperature in an open furnace can produce a runaway reaction with a white SnO2 cloud. Store in dry, airtight containers under inert gas if shelf life beyond a few months matters; humidity slowly oxidizes the surface to a black SnOx layer that throws off stoichiometry in thin-film deposition.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals. We deliberately do not publish occupational exposure limits or other regulatory thresholds: those values are revised over time and differ between jurisdictions, so the only correct source is the current SDS and the regulations that apply where you work.