Sol-gel 법을 이용한 Thermochromic 박막제조 및 특성

Abstract

ABSTRACT

Properties and preparation of Thermochromic thin film by Sol-gel method

Byun Young joon (Co. directed by Prof. Duck Kyun Choi, Dr. Jeong Ho Cho, Ph. D.) Dept. of Ceramic Engineering Graduate School Hanyang University

Vanadium dioxide VO2 is known to undergo a reversible semiconductor-metal transition around 68℃ associated with a structural phase transformation from monoclinic to tetragonal. The high temperature phase has a tetragonal rutile structure characterized by chains of edge sharing octahedra along the c axis with equidistant vanadium atoms. Vanadium paring occurs below 68℃ giving rise to a monoclinic phase with alternate shorter and longer V-V distances. The switching temperature together with the shape of the hyterisis loop can and be modified by doping VO2 films with foreign cations. The switching temperature is decreases and increase by doped MxVO2 ( M=W6+, Nb5+, Ti4+, Cr3+ or Al3+) thin films, Lowering the temperature can be easily obtained with tungsten cations (W+6) precursors. Thin films of vanadium dioxide(VO2)-vanadium tungsten (VO2-WO3) on glass substrates were prepared by inorganic sol-gel methods. The process parameter were temperature, time, and reduction gas. In conclusion, the temperature at which the switching occurs decreases progressively when VO2 films are doped with W6+. In the same time the jumping order also decreases. Switching occurs below 33℃ when the films is doped with 2mol% of W6+.