""Nonstoichiometric REEAl(2.07)(B(4)O(10))O(0.60) (REE =La, Pr) borates have been crystallized and analyzed by means of single crystal X-ray diffraction. The compounds resulted to be isostructural within hexagonal space group P (6) over bar 2m (n. 189), with the following unit cell parameters: a = 4.6170(1) angstrom, c = 9.3640(3) angstrom and V= 172.87(1) angstrom(3) (La); a = 4.5990(1) angstrom; c = 9.3270(2) angstrom and V = 170.87(1) angstrom(3) (Pr). REE cations make up a trigonal prismatic coordination, by means of six REE-O bonds under 2.5 angstrom; aluminium cation is five-coordinated, displaying a square pyramidal coordination, while the boron atom forms BO(4) tetrahedral units. The present borates belong to the structural type of NdAl(2.07)(B(4)O(10))O(0.60) dimetaborate [I]: thus, the three-dimensional framework can be described as a structure packed down crystallographic axis c, with layers of six-membered rings of B tetrahedra alternated by inter-layers REE cations and layers of Al polyhedra. An intricate network of Al center dot center dot center dot O and REE center dot center dot center dot O interactions complete the array.""
Capitelli, F., Chita, G., Leonyuk, N.i., Koporulina, E.v., Bellatreccia, F., DELLA VENTURA, G. (2011). REEAl<sub>2.07</sub>(B<sub>4</sub>O<sub>10</sub>)O<sub>0.60</sub> dimetaborates (REE = La, Pr); synthesis and X-ray structural characterization. ZEITSCHRIFT FUR KRISTALLOGRAPHIE, 226, 219-225 [10.1524/zkri.2011.1310].