SINGLE-CRYSTALS GROWTH OF HUO(2)PO(4.)4H(2)O (HUP)

A method is proposed to grow HUO(2)PO(4.)4H(2)O (HUP) single crystals by diffusion-precipitation in a U-tube from H3PO4 and an uranyl salt i n a gellified medium of TES (tetraethoxysilane). Parameters affecting the growth process (density and aging of gel, temperature and rate of precipitation, pH of solutions) were taken into account Large single c rystalline platelets of maximal size (2 x 2 x 0,5) mm were obtained an d characterized by x-ray diffraction, FTIR, optical microscopy and SEM . Crystalline orientation was evaluated by Laue method. HUP is an exce llent solid protonic conducting material which can be employed in soli d state batteries, gas sensors electrochromic displays, superionic cap acitors, etc.