Orthoborates processed by soft routes: correlation luminescence structure

YBO3 and H-Ln BO3 (Ln=La, Nd, Sm, and Eu) orthoborates have been prepared b y an original sol-gel mineral pIocess. This synthesis method over solid sta te reaction offers the possibility of obtaining high quality materials at l ow temperatures, without parasitic phases. Luminescent europium ions have b een used as structural probes to investigate these orthoborate phases. Due to the purities of the different powders the symmetries of the europium ion in the different matrices have been determined unambiguously and a compari son between the luminescence results and the structural descriptions given in the literature has been realized. (C) 2001 Published by Elsevier Science B.V.