Gd4B4O11F2: Synthesis and crystal structure of a rare-earth fluoride borate exhibiting a new “fundamental building block” in borate chemistry

Synthesis of Er5(BO3)2F9 and Properties of RE5(BO3)2F9 (RE = Er, Yb)

“…There is a close relationship between these two structure-types and the recently discovered high-pressure ytterbium fluoride borate Yb 5 (BO 3 ) 2 F 9 [1]. All three compounds can be described via alternating layers of the formal compositions "REBO 3 " and "REF 3 " in the bc-plane. It should be emphasized that the crystal structures of the actual compounds REBO 3 and REF 3 can not be compared with the structures of the layers, so that "REBO 3 " and "REF 3 " only stand for the formal composition of the layers.…”

“…Bands in this range usually indicate OH-groups in watercontaining borates. The substitution of fluoride with hydroxyl groups is a problem commonly known from fluoride borates [3,4]. The single crystals, which were examined via IR spectroscopy, have been exposed to air and humidity and were not dried under high vacuum like the bulk material of Yb 5 (BO 3 ) 2 F 9 .…”

“…In the past years, the field of rare-earth fluorido-and fluoride borates could be greatly extended by the application of high-pressure / high-temperature techniques, leading to the new compounds Yb 5 (BO 3 ) 2 F 9 [1], Pr 4 B 3 O 10 F [2], and Gd 4 B 4 O 11 F 2 [3].…”

“…Before we started our high-pressure / high-temperature research, rare-earth fluorido-and fluoride borates were only represented by the compounds RE 3 (BO 3 ) 2 F 3 (RE = Sm, Eu, Gd) [4] and Gd 2 (BO 3 )F 3 [5], synthesized by heating a stoichiometric mixture of RE 2 O 3 , B 2 O 3 , and REF 3 under ambient pressure conditions. There is a close relationship between these two structure-types and the recently discovered high-pressure ytterbium fluoride borate Yb 5 (BO 3 ) 2 F 9 [1].…”

“…All three compounds can be described via alternating layers of the formal compositions "REBO 3 " and "REF 3 " in the bc-plane. It should be emphasized that the crystal structures of the actual compounds REBO 3 and REF 3 can not be compared with the structures of the layers, so that "REBO 3 " and "REF 3 " only stand for the formal composition of the layers. We are now trying to substitute the Yb 3+ ions of Yb 5 (BO 3 ) 2 F 9 with other rare-earth cations to yield isotypic RE 5 (BO 3 ) 2 F 9 phases, different structures, or new compositions dependent of the size of the rare-earth ion.…”