The decomposition of metal (Ti, Zr, Sn) alkoxides at 250 deg. C in a solution of tetradecene and dodecylamine resulted in the formation of ultra-small (1-2 nm) oxide nanoparticles. The nanoparticles showed unusual structural properties. The high-pressure orthorhombic phase was found for SnO{sub 2}. The as-synthesized ZrO{sub 2} nanoparticles were only partially crystallized. It was possible to observe their in situ crystallization under the TEM beam. The TiO{sub 2} nanoparticles appeared amorphous, with only a few nanocrystals dispersed in the sample. The temperature evolution of the samples was investigated in situ by Raman spectroscopy. All SnO{sub 2} was converted to stable cassiterite at 350 deg. C. TiO{sub 2} and ZrO{sub 2} samples displayed phase stability reversal over a broad range of temperatures.