Abstract
The new ternary transition metal borides Mn3‐xIr5B2+x (0≤x≤0.5) and Mn2IrB2 were synthesized from the elements under high temperature and high‐pressure/high‐temperature conditions. Both phases can be synthesized as powder samples in a radio‐frequency furnace in argon atmosphere. High‐pressure/high‐temperature conditions were used to grow single‐crystals. The phases represent the first ternary compounds within the system Mn–Ir–B. Mn3−xIr5B2+x (0≤x≤0.5) crystallizes in the Ti3Co5B2 structure type (P4/mbm; no. 127) with parameters a=9.332(1), c=2.896(2) Å, and Z=2. Mn2IrB2 crystallizes in the β‐Cr2IrB2 crystal structure type (Cmcm; no. 63) with parameters a=3.135(3), b=9.859(5), c=13.220(3) Å, and Z=8. The compositions of both compounds were confirmed by EDX measurements and the compressibility was determined experimentally for Mn3−xIr5B2+x and by DFT calculations for Mn2IrB2.
Highlights
Metal borides display a variety of very interesting physical properties such as a high hardness (ReB2, WB4, FeB4, IrB1.35),[1] low compressibility (OsB2, Re7B3),[2] magnetic properties (Nd2Fe14B),[3] high transition temperature into a superconducting state (MgB2),[4] and a very high electron emissivity (LaB6).[5]
Most borides can be synthesized at ambient pressure and are relatively inexpensive and accessible, which makes them interesting materials for industrial usage.[1a,b,6] Very few compounds exhibit such a huge structural variety as borides do, which can be seen from the existence of more than 1000 binary and ternary borides that crystallize in over 150 different structure types.[7]
With the synthesis of Mn2IrB2 and Mn3ÀxIr5B2+x (0 x 0.5), we have synthesized the first two ternary borides containing manganese and iridium. Both phases can be synthesized by hightemperature techniques but high-temperature/high-pressure conditions were used to improve the quality of the single crystals
Summary
Metal borides display a variety of very interesting physical properties such as a high hardness (ReB2, WB4, FeB4, IrB1.35),[1] low compressibility (OsB2, Re7B3),[2] magnetic properties (Nd2Fe14B),[3] high transition temperature into a superconducting state (MgB2),[4] and a very high electron emissivity (LaB6).[5]. We report the synthesis of Mn2IrB2, representing the first ternary Mn–Ir–B compound and the second known phase adopting the b-Cr2IrB2 structure type. The Ti3Co5B2 structure type (in general A3T5B2), which was first described by Kuz’ma et al in 1971, and including related structures, such as the quaternary substitution variant with the general formula of A2MT5B2, is one of the most common structure types within metal-rich borides.[12] In the quaternary variant, the “Ti” position is split into two different crystallographic sites with different coordinations: a pentagonal-prismatic “A”-position and a tetragonal-prismatic coordinated “M”-position. With the successful synthesis of Mn3ÀxIr5B2+x (0 x 0.5), a new ternary member with a magnetic active element (Mn) at the important “M” position can be added to the important family of compounds crystallizing in the Ti3Co5B2 structure type
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