Formation of Edge‐Sharing BO₄ Tetrahedra in the High‐Pressure Borate HP‐NiB₂O₄

Abstract

In the course of our structural investigations of borates synthesized under high-pressure, high-temperature conditions, we discovered several new high-pressure modifications [1][2][3][4][5] with interesting structural features and physical properties, for example, a new non-centrosymmetric modification of bismuth triborate (d-BiB 3 O 6 ).[6] Along with the investigation of these phase transitions, we aim to synthesize borates with new compositions, whose existence is presumably based on high-pressure conditions during synthesis. Examples are the borates RE 3 B 5 O 12 (RE = Tm-Lu), [7] RE 4 B 6 O 15 (RE = Dy, Ho), [8][9][10] a-RE 2 B 4 O 9 (RE = SmHo), [11][12][13] b-RE 2 B 4 O 9 (RE = Gd, Dy), [14,15] and Pr 4 B 10 O 21 , [16] which have no corresponding ambient-pressure modifications. To our surprise, the borates RE 4 B 6 O 15 (RE = Dy, Ho) [8][9][10] revealed edge-sharing as well as corner-sharing BO 4 tetrahedra; such edge-sharing tetrahedra had been previously unknown in the varied structural chemistry of borates. Later on, we discovered a second type of structure, a-RE 2 B 4 O 9 (RE = Sm-Ho), [11][12][13] that also display this new structural feature. Herein, we report the synthesis and characterization of a new nickel borate HP-NiB 2 O 4 , in which each BO 4 tetrahedron shares a common edge with a second BO 4 tetrahedron.In the system NiO-B 2 O 3 , there is only one nickel borate, of the composition Ni 3 (BO 3 ) 2 . [17][18][19][20] This compound displays trigonally coordinated boron atoms and Ni 2+ ions with octahedral coordination. Recently, Pompetzki and Albert found a new synthetic route to pure Ni 3 (BO 3 ) 2 ; they employed the thermal decomposition of a mixture of NiCO 3 ·2 Ni(OH) 2 ·4 H 2 O and H 3 BO 3 .[21] In our own investigations of the Ni-B-O ternary system, we synthesized a second borate of the composition b-NiB 4 O 7[22] under high-pressure conditions of 7.5 GPa and at a temperature of 1000 8C; this compound has a structure analogous to the high-pressure modification b-ZnB 4 O 7 .[5] With HP-NiB 2 O 4 , we have now found a third composition in the Ni-B-O ternary system, which accentuates the performance of high-pressure synthesis in solid-state chemistry.HP-NiB 2 O 4 was synthesized in a high-pressure, hightemperature reaction at 7.5 GPa and 680 8C in a modified Walker module (multianvil assembly) starting from the oxides NiO and B 2 O 3 [Eq.(1)]. [23] NiO þ B 2 O 3 !HP-NiB 2 O 4 ð1Þ

Lattice dynamics and a magnetic-structural phase transition in the nickel orthoborateNi3(BO3)2Pisarev1, Prosnikov2, Davydov3 et al. 2016Phys. Rev. B221100View full textAdd to dashboardCite

“…We add that the above mentioned high-pressure borate NiB2O4 shows similar optical features and is characterized as "light-green" [55]. Lines are guides to the eye.…”

“…The nickel borate Ni3(BO3)2 is known for more than a century [13], whereas other borates, NiB2O4 and NiB4O7, were synthesized only recently, under high-pressure and high-temperature conditions [55,56]. For our studies, single crystals of Ni3(BO3)2 were grown by a gas-transport method in the evacuated quartz ampoules along with the nickel boracites single crystals [16].…”

Electrochromic Characteristics of a Nickel Borate Thin Film Investigated by In Situ XAFS and UV/vis Spectroscopy

“…15,16 The nickel borate compounds Ni 3 (BO 3 ) 2 and Ni(BO 2 ) 2 have been investigated as candidates for several applications based on this unique behavior. [17][18][19][20][21] Recently, Dincă et al reported that a nickel borate thin film electrodeposited from a dilute Ni 2+ solution in a borate electrolyte (a so-called Ni-B i thin film) functions as an efficient electrocatalyst in an oxygen evolution reaction. 22 The characteristics of these Ni-B i thin films were investigated by Ni Kedge X-ray absorption fine structure (XAFS) and electrochemical kinetics, and it was found that the average valence state of the nickel species changes from +2.0 to +3.6 in response to an applied positive voltage.…”

Synthesis and Crystal Structure of the New High‐Pressure Phase CdB2O4

“…RE 4 B 6 O 15 (RE = Dy, Ho), [14][15][16] a-RE 2 B 4 O 9 (RE = Sm-Ho), [17][18][19] and the recently found HP-NiB 2 O 4 [20] show, besides new compositions, the new strucural motif of edge-sharing BO 4 -tetrahedra. HPNiB 2 O 4 is the first borate, in which every BO 4 -group shares one common edge with an adjacent BO 4 -tetrahedron.…”