SiO${}_2$-mediated facile hydrothermal synthesis of spiroffite-type Co${}_2$Te${}_3$O${}_8$

The hydrothermal synthesis of novel materials typically relies on both knowledge of the redox activities of all cations present in the reaction solution and a small toolset of so-called mineralizers to tune the solution’s overall chemical potential. Upon the use of a less conventional mineralizer species, SiO${}_2$, we show the stabilization of spiroffite-type Co${}_2$Te${}_3$O${}_8$ under less forceful hydrothermal conditions than in previous reports. When synthesized in the presence of both SiO${}_2$ and each respective alkali carbonate as a secondary mineralizer, silicon substitution in place of tellurium in the host structure becomes apparent, and the corresponding introduced disorder gives rise to enhanced low-temperature ferromagnetism. Our results highlight the complexities of underutilized and combined mineralizer species in the stabilization and tuning of complex magnetic ground states via hydrothermal synthesis techniques.