In this study, we propose a wet chemical method, called ammonium-nitrate-melt-technique, for the synthesis of any type of bulk oxide compounds. This method was successfully applied to the high-T_c superconductors (Y-123, Ru-2212, etc), diluted magnetic semiconductors (Ti_1-xCoO₂) and hard magnetic barium ferrites (BaFe₁₂O₁₉). For instance, we have obtained a single phase M-type barium ferrites with finely granular structure at nanoscale (300-400 nm). Magnetic parameters of these samples are near to the theoretically estimated values. Besides, superconducting transition temperature of ∼70 K was observed in ferromagnetism&superconductivity co-existed ruthenates, which is only possible at very high oxygination pressures (600 atm). Consequently, we believe that the method will attract the attention of many material scientists.