Research in the field of non-linear optical (NLO) devices lead to an increasing interest in new borate compounds, capable of expanding the frequency range provided by common laser sources. Lithium triborate (LBO) is a newly developed ideal non-linear optical crystal used in laser weapon, welder, radar, tracker, surgery, communication, etc. In this study, synthesis and identification of rare-earth doped lithium triborate was carried out. Borates containing rare-earth elements are of great interest since they are found to be superior in non-linear optical applications. Lithium triborate was produced from the solid-state reaction. Lithium triborate was then doped with some rare-earth elements (Gd, La, Y, etc.) in several different concentrations. In this study, LBO samples doped with Gd are presented. Characterization of the new products was done by X-ray diffraction (XRD) and infrared (IR) analysis. Differential thermal analysis (DTA) was used for examination of the thermal properties of the compounds, morphology of new compounds was observed by scanning electron microscopy (SEM). The compounds are then subjected to thermoluminescence (TL) studies. From the XRD, studies, no change related to addition of the rare-earth elements was observed. IR analysis showed that there is no change related to B-O link with the addition of rare-earth elements. DTA studies showed that the melting point of LBO decreases with the addition of rare-earth elements. In the SEM images, particles of rare-earth elements and lithium triborate were observed clearly. (c) 2005 Elsevier B.V. All rights reserved.