2026-10-11T14:32:47Z https://api.figshare.com/v2/oai

oai:figshare.com:article/33906373 2026-09-17T18:06:02Z category_4 category_146 category_12 category_16 category_873 category_106 category_45 category_135 portal_63 item_type_2 month_year_09_2026

Phase Selectivity in Borate Flux Synthesis Using Refractory Additives Gregory Bassen (18465833) Allana G. Iwanicki (25042096) Maxime A. Siegler (1298370) Sarah Okandey (25042099) Elaine Flowers (25042102) Rebecca Han (1818550) Sydney Reiser (25042105) Brandon Wilfong (3389180) Davor Tolj (17755727) Tyrel M. McQueen (1494640) Biochemistry Space Science Cell Biology Physiology Chemical Sciences not elsewhere classified Science Policy Sociology Computational Biology unconventional materials stabilization two distinct classes reaction shows cub ray μct imaging heterogeneous nucleation substrate crystal growth methods coordinated borate monomers coordinate boron tetrahedra accessing new materials grew single crystals directing phase formation 5 –</ sup 2 +</ sup ex situ x differentiate refractory additives provide challenge cases susceptible refractory additive 10 )°, β 6 </ sub 16 </ sub 2 </ sub resistant refractory additives borate flux synthesis 3 </ sub >< sub >< 4 </ sub previously reported cu refractory additives Here, we report a novel approach to borate flux synthesis in which refractory oxide additives alter reaction phase outcome. In the absence of refractory additives, reactions of copper oxide and boron oxide flux yielded single crystals of the previously reported Cu₁₅(BO₃)₆(B₂O₅)₂O₂ (Cu₃B₂O₆), containing solely trigonal planar-coordinated borate monomers and dimers. Addition of TiO₂ led to the discovery of a novel structural prototype Cu_{7–<i>x</i>+<i>y</i>}Ti_<i>x</i>(BO₃)(B₂O₅)(B₃O₇)O (Cu_{7–<i>x</i>+<i>y</i>}Ti_<i>x</i>B₆O₁₆), which crystallizes in space group <i>P</i>1̅, with <i>a</i> = 3.31989(4) Å, <i>b</i> = 10.54906(13) Å, <i>c</i> = 17.9143(2) Å, α = 75.5076(10)°, β = 88.8619(10)°, and γ = 86.7381(10)° for <i>x</i> = 0.276(7), <i>y</i> = 0.0135(15). It consists of quasi-2D layers of Cu²⁺ cations enclosing trigonal planar borate monomers, dimers, and the uncommon (B₃O₇)^5– trimer. Adjacent layers are connected by oxygen and disordered Cu/Ti sites. In contrast, both ZrO₂ and HfO₂ grew single crystals of the previously reported material CuB₂O₄ containing solely tetrahedrally coordinated boron in a 3D framework. Ex situ X-ray μCT imaging of the ZrO₂ reaction shows CuB₂O₄ crystals growing at the interface of ZrO₂ and the flux, suggesting that ZrO₂ (and by extension, HfO₂) acts as a heterogeneous nucleation substrate that stabilizes the four-coordinate boron tetrahedra. Magnetization of Cu_{7–<i>x</i>+<i>y</i>}Ti_<i>x</i>B₆O₁₆ is reported, showing an antiferromagnetic transition at <i>T</i>_<i>N</i> = 12.8 K. We then differentiate refractory additives into two distinct classes, flux-resistant and flux-susceptible, with ZrO₂ and HfO₂ as B₂O₃-flux-resistant refractory additives and TiO₂ as a B₂O₃-flux-susceptible refractory additive. These results demonstrate that refractory additives can provide a useful handle for directing phase formation and accessing new materials in flux synthesis, and provide challenge cases to benchmark emerging AI models in unconventional materials stabilization and crystal growth methods. 2026-09-17T00:00:00Z Dataset Media 10.1021/acs.chemmater.6c01919.s002 https://figshare.com/articles/media/Phase_Selectivity_in_Borate_Flux_Synthesis_Using_Refractory_Additives/33906373 CC BY-NC 4.0