Vaterite type YBO 3 and GdBO 3 and aragonite type LaBO 3 were prepared by the combustion. Combustion synthesis is a straightforward method to produce nanocrystalline powders requiring only a simple apparatus. The reaction was carried out by heating a mixture of rare earth nitrates, orthoboric acid and an organic fuel. For each RBO 3 , the ratios of starting materials were varied to obtain the optimal combustion reaction. The combustion synthesized RBO 3 were characterized with X-ray powder diffraction and FT-IR spectroscopy. The FT-IR spectra showed also the expected impurities of the combustion reaction (CO 2 , H 2 O and NO x ). The thermal stability of RBO 3 was studied with thermogravimetry and FT-IR spectroscopy. The post-annealing completed the formation of the RBO 3 , reduced the amount of impurities in the materials, improved the crystallinity, and increased the crystallite size. The mean crystallite size of the as-prepared and post-annealed YBO 3 was calculated using the Scherrer method. The excitation and luminescence spectra of the Eu 3+ doped LaBO 3 were collected at 77K. The spectra of the as-prepared LaBO 3 :Eu 3+ showed the typical features for the Eu 3+ ion with a low site symmetry.