Cesium can be encapsulated in crystalline aluminosilicates or borosilicates of ANA framework type by hydrothermal synthesis from alkaline solutions at a temperature as low as 115 degrees C. No miscibility gap is observed in the borosilicate-aluminosilicate solid solution. The presence of cesium in the synthesis batch slightly decreases the yield of incorporation of boron in the silicate framework. Nanocrystals from 25 to 50 nm are formed in most of the synthesis conditions. (C) 2010 Elsevier B.V. All rights reserved.