Methodological Approach to the High-Pressure Synthesis of Nonmagnetic Li₂B⁴⁺B′⁶⁺O₆ Oxides

Abstract

High-pressure solid-state synthesis advances boost discoveries of new materials and unusual phenomena but endures stringent recipe conditions, poor yield, and high cost. A methodological approach for accelerated and precisely high-pressure synthesis is therefore highly desired. Here, we take the exotic double-perovskite-related nonmagnetic Li2 B +4 B′+6O6 as an example to show the pipeline of data-mining, high-throughput calculations, experimental realization, and chemical interception of metastable phases. A total of 140 compounds in 7 polymorph categories were initially screened by the convex hull, which left ∼50% candidates in chemical space on the phase diagram of pressure-dependent polymorph evolution. Li2TiWO6 and Li2TiTeO6 were singled out for experimental testing according to the predicted map of crystal structure, function, and synthesis parameters. Computation on surface energy effect and interfacial chemical strain suggested that the as-made high-pressure R3-Li2TiTeO6 polymorph cannot be intercepted below a critical nanoscale but can be stabilized in heterojunction film on a selected compressive substrate at ambient pressure. The developed methodology is expected to accelerate the big-data-driven discovery of generic chemical formula-based new materials beyond perovskites by high-pressure synthesis and shed light on the large-scale stabilization of metastable phases under mild conditions.

High-Pressure Synthesis of Polar and Antiferromagnetic Mn2MnMoO6

“…As shown in Table S2, the bond distance of Mn–O ranges from 2.050(13) to 2.390(11) Å and that of Mo–O from 1.859(9) to 1.988(18) Å, rendering strong anisotropy and large P s calculated to be 65.76 μC·cm –2 by the point charge model . Previous research demonstrates that, for polar-corundum-type derivatives, the polarization reversal barrier ( E barrier ) of the domain wall shows a strong correlation to the local bonding environment of A-site cations, as can be evaluated by normalized bond-valence sums (BVS). ,,− On this basis, the E barrier of Mn 2 MnMoO 6 is estimated to be about 232 meV (Figure b), which is between the values of Mn 2 FeMoO 6 , and Mn 2 MnWO 6 . The average ⟨Mn1–O⟩ bond length (2.170 (15) Å) in Mn 2 MnMoO 6 is comparable with those in Mn 2 MnWO 6 (2.00 Å) and Mn 2 FeMoO 6 (2.195 Å) .…”

“…“*” Represents an unknown impurity. (b) Comparison of E barrier between Mn 2 MnMoO 6 and other polar-corundum compounds. ,,− Reprinted with permission from ref . Copyright 2021 American Chemical Society.…”

Comparative Study on the Magnetic and Transport Properties of B-Site Ordered and Disordered CaCu3Fe2Os2O12

“…It possesses a very high ferrimagnetic Curie temperature T C of 580 K and a considerable magnetic moment of 5.0 μ B /fu. The charge and spin configuration is Cu 2+ (↑)­Fe 3+ (↑)­Os 5+ (↓), quite analogous to some other isostructural systems ,, and with also signs for the presence of orbital moments. , It is worth noting that CCFOO was synthesized under the high-pressure and high-temperature (HPHT) method, which is able to stabilize the metastable phase at ambient pressure. − …”

Metastable γ-Li2TiTeO6: Negative Chemical Pressure Interception and Polymorph Tuning of SHG

“…Seven polymorphs are known for the exotic perovskiterelated A 2 BB′O 6 compounds, among which Li 2 BTeO 6 are more likely to crystalize in R3-OIL, Pnn2, R3-NTO, and P21/n structures. 37 Here, the E−V curves for the above four possible polymorphs were computed for LTTO using DFT, as shown in Figure 3b, where the α-phase (Pnn2) is the most stable one with the lowest internal energy at V 0 (ambient pressure), docking on the energy convex hull of the phase diagram (thermodynamically stable phase) 49 and can be synthesized by the conventional solid-state reaction at ambient pressure. 50 The energy of the β-phase (NTO-type R3) becomes lower than that of the α-phase above 6 GPa as has been experimentally validated in our previous work.…”

“…LTTO was found to transform from stable Pnn2 (α) to metastable Ni 3 TeO 6 (NTO)-type R3 (β) under high pressure (6 GPa) upon temperature quenching as predicted. 37 Given the similar chemical compositions and local structure between β-LTTO and Na 2 TiTeO 6 (NTTO), it is thus expected to obtain a metastable LTTO phase via the topotactic reaction. Here, we revisited the structure of NTTO and found out that NTTO adopts the ordered-ilmenite (OIL)-type R3 structure rather than the reported ilmenite (R3̅ ) symmetry.…”