X-ray powder diffraction studies and thermal behaviour of NaK2B9O15, Na(Na.17K.83)2B9O15, and (Na.80K.20)K2B9O15

Thermal “order‐disorder” behaviour in (Na1‐xKx)4B8O14 solid solutions investigated by X‐ray powder diffraction

“…We observed a similar situation earlier on when studying K 3 B 9 O 15 , a structure in which the presence of three different-sized cationic sites leads to the formation of a new ordered compound as well as of a solid solution [8].…”

“…In the Na 2 O-K 2 O-B 2 O 3 ternary system the existence of (K,Na)BO 2 solid solutions have been described in the 1:1 section [7], but no structural data was reported for these phases. Our earlier studies led to the discovery of a new ordered compound, NaK 2 B 9 O 15, and solid solutions (Na 1-x K x ) 3 B 9 O 15 , 0.45 ≤ x<1.0 [8]. The crystal structures of NaK 2 B 9 O 15 , Na(Na .17 K .83 ) 2 B 9 O 15 and (Na .8 K .2 )K 2 B 9 O 15 have been refined by the Rietveld method, and phase relationships as well as the thermal behavior of the solid solutions were studied by X-ray powder diffraction [8].…”

“…Our earlier studies led to the discovery of a new ordered compound, NaK 2 B 9 O 15, and solid solutions (Na 1-x K x ) 3 B 9 O 15 , 0.45 ≤ x<1.0 [8]. The crystal structures of NaK 2 B 9 O 15 , Na(Na .17 K .83 ) 2 B 9 O 15 and (Na .8 K .2 )K 2 B 9 O 15 have been refined by the Rietveld method, and phase relationships as well as the thermal behavior of the solid solutions were studied by X-ray powder diffraction [8]. Structural data exists on one more mixed borate, KNa 2 BO 3 , only [9].…”

Na2Rb2SrB18O30 with [B9O19]11− fundamental building block consisting of three [B3O7]5− groups

“…According to the connection mode of [B 9 O 19 ] 11− FBB, they can be divided into two types (Figure 2). (1) Type I: two [B 3 O 7 ] 5− groups connect with third [B 3 O 7 ] 5− via vertex‐sharing of oxygens from BO 3 and BO 4 units, respectively, such as KB 3 O 5 (or A x A’ y (B 3 O 5 ) 3 (A=Na, A’=K, x + y =3)) [38–39] . According to topological structure, (Na 0.8 K 0.2 )K 2 (B 3 O 5 ) 3 , NaK 2 (B 3 O 5 ) 3 , KB 3 O 5 , and Na(Na 0.17 K 0.83 ) 2 (B 3 O 5 ) 3 belong to Schläfli symbol of {4 2 ;6 4 }2{6 6 }; (2) Type II: two [B 3 O 7 ] 5− groups connect with third [B 3 O 7 ] 5− via vertex‐sharing of oxygens only from BO 4 units, such as AMB 9 O 15 (A=Li and Na, M=Sr and Ba) [40] and AA'M'B 18 O 30 (A=Li and Na, A’=Rb and Cs, M’=Sr, Ba and Pb) [41–43] .…”

α-LiMB9O15 (M = Sr, Pb): flexible [B3O7] units leading to the low temperature phase of β-LiMB9O15 (M = Sr, Pb)

“…However, for β-LiPbB 9 O 15 , only in part of the tunnels, the Li and Pb atoms are arranged in a line, but the rest are not, and the B–O frameworks of ABaB 9 O 15 (A = Li, Na) are similar to those of β-LiSrB 9 O 15 , while CsBaB 9 O 15 crystallizes in the Cc space group and features a 2D double layer structure with the [B 9 O 19 ] groups as FBUs; 62 Besides, NaK 2 B 9 O 15 , Na(Na 0.17 K 0.83 ) 2 B 9 O 15 and (Na 0.80 K 0.20 )K 2 B 9 O 15 are isostructural and crystallize in the space group P 2 1 / c , featuring 3D B–O frameworks constructed from [B 3 O 7 ] groups. 63 Accordingly, the B–O frameworks of α-LiMB 9 O 15 (M = Sr, Pb) are different from other reported B 9 O 15 classes and enrich the structural chemistry. Moreover, the FBU and frameworks of similar B 3 O 5 /B 9 O 15 /B 18 O 30 classes of borates are illustrated in Table S6 †…”