This technology is based on the use of water fluid as a reaction medium for synthesis of fine-crystalline oxides. The production of fine-crystalline oxides in a pilot plant using the industrial autoclaves has demonstrated the economical expediency and environmental safety of manufacturing of various fine-crystalline oxides by this method. The synthesis is performed at temperature in the range 380-410 degrees C and pressure of the water fluid 10-30 MPa in a high-pressure apparatus (reactor, autoclave or gasostat). Both the simple and mixed oxides with crystal sizes ranged from 100 nm to 400 mu m were synthesized including quartz, corundum, zincite, aluminates of alkaline earth and rare earth elements, barium hexaferrite and yttrium-aluminum garnet. (C) 2007 Elsevier B.V. All rights reserved.