The crystal structure of cesium triborate, Cs2O.3B2O3

Crystalline cesium triborate, Cs20.3 B203, has been prepared and the structure determined.The crystals belong to the space group P212121, with unit-cell dimensions a=6.18, b=8.48, c-9.17 A.A complete set of atomic parameters has been determined from electron-density projections along the two shortest axes.The structure has one out of every three boron atoms four-fold coordinated by oxygen, the other two being three-fold coordinated.The basic unit of the structure is a sixmembered ring, interlinked with identical rings to a continuous three-dimensional network.The structure is related to the structure of some other crystalline and vitreous alkali borates.It is shown that the fraction of boron atoms in four-fold coordination in the known alkali borate structures is a simple function of the alkali content up to the diborate composition.