Voltage-induced phase transition of VO2@SiO2 nanoparticles

Abstract

As a typical metal oxide with a strong electronic correlation, vanadium dioxide (VO2) has great application potential in over-pulse protection, new storage devices, and field-effect switches. However, its chemical instability and low dispersibility have restricted its application in these areas. The synthesis of VO2@shell nanoparticles may improve VO2's oxidation resistance. Herein, VO2@SiO2 core-shell nanoparticles with different coating thicknesses are synthesized via the Stöber method. The coated VO2's oxidation temperature is 45 °C higher than that of the uncoated sample. However, the phase-transition temperature of the coated samples remains unaffected (68 °C). A VO2@SiO2 composite material is prepared by mixing VO2 with a polyvinyl pyrrolidone matrix. When the SiO2 coating thickness is less than 3 nm, the composite material undergoes temperature and electro-induced phase transitions. As a result of temperature changes and high voltage application, the resistance of the material can suddenly change. Moreover, the material resistance increases with increasing coating thickness. When the thickness of the material exceeds 3 nm, the room temperature resistance of the material sharply increases. The temperature-induced phase transition of the composite material is not clearly observed. In addition, repeated electro-induced phase transition cannot occur. The nonlinear coefficient of the electro-induced phase transition of the VO2@SiO2 composite material filled with coated particles is improved, particularly when the coating thickness exceeds 2 nm. Our results indicate that SiO2 coating can improve both oxidation resistance and electro-induced phase transition performance of VO2. The optimal coating thickness was between 2 and 3 nm. These findings are of great importance to promote the practical applications of VO2.