Difference between revisions of "Mechadensite"

Revision as of 11:30, 10 June 2022

This is not an official name.
Allow me (author of this wiki) to be so vain as to name an unnatural and
not yet synthesizable gemstone with my main internet pseudonym.

Stoichometry and examples

The mechadensite series:

• General formula: Si_xTi_yO_z 2*(x+y)=z

Examples:

• SiTiO₄ (equistoicometric mechadensite)
• Si₃TiO₈ (silicon leaning mechadensite – presumably more hardness and less thermal stability)

End members are:

• rutile TiO₂ and
• stishovite SiO₂ (isostructural to rutile thus not quartz).
  

Likely propertiers

• high hardness (Mohs 6 to Mohs 9)
• electrically non conductive wide band-gap
• optically transparent in visible spectral range
• strong optical dispersion
• high heat conductance (but far from diamond)

Not a solid solution mixing series

Regarding "mixing series" note that this is meant as a piezomechanosyntesized checkerboard compound.
It is not supposed to be a thermodynamic solid solution with statistically distributed (random) placement of atoms.
Such a solid solution might not even be accessible via thermodynamic production pathways,
that is melting mixing and recrystallizing.
It should be quite easy to figure out which Ti/Si ratios allow for symmetric checkerboard patterns
with extended unit cells of minimal size.

Related

• Pseudo phase diagram

What is so special about this gemstone? …
Rutile TiO₂ is limited in hardness (Mohs 6 to 6.5) but thermally highly stable.
Stishovite SiO₂ is ultra hard (Mohs 8.5 to 9) but likely thermally less stable since
it's a metastable high pressure modification of quartz (SiO₂ too).

A "mixing series" may allow for combining the advantages of both by
tuning the Si/Ti ratio such that the material attains both high mechanical and high thermal stability.