Co掺杂比例对ZnO热致变色变发射率性能的影响

Influences of Co^(2+) Doping Ratio on the Thermochromic and Variable Emissivity Properties of ZnO

利用固相烧结法制备了不同Co^(2+)掺杂比例的ZnO,研究了Co^(2+)掺杂比例对ZnO微观结构形貌,从而对变色变发射率性能的影响。结果表明,Co^(2+)掺杂会取代ZnO中部分的Zn^(2+),但不改变ZnO的六方纤锌矿结构。掺杂比例达到7.5%和10%时,会形成杂相Co_3O_4。随着掺杂比例逐渐增加,ZnO的结晶质量下降、禁带宽度减小、而晶粒形貌尺寸基本不变。Co^(2+)掺杂ZnO在室温下都呈绿色,随掺杂比例增加颜色先变深后变浅。当温度从室温升高到700℃,所有样品可变为黄褐色同时发射率逐渐提高。并且,随掺杂比例增加,颜色变化更为明显,发射率变化值增大。

The ZnO powders doped by different ratios of Co^2+ions were synthesized via solid-state reaction.The effects of Co^2+doping ratio on microstructure and morphology,and thus on thermochromic and variable emissivity properties of ZnO were studied in detail.The results show that Co^2+ions would substitute for part of the Zn2+ions in ZnO,and it does not change wurtzite(hexagonal)zincite crystal structure of the ZnO.While when doping ratio reaches 7.5%and 10%,impurity phase Co3O4 would form in the samples.The crystal quality and forbidden bandwidth of ZnO decreases gradually while morphology and grain size of ZnO barely change with doping ratio of Co^2+ions increasing.The Co^2+doped ZnO powders are green at room temperature,which gets deep initially and then becomes shallow with Co^2+content increasing.When the testing temperature improves from room temperature to 700℃,all the samples could turn into tawny color and the emissivity increases simultaneously.And the color change is more obvious and the change value in emissivity increases with enhancement of Co^2+doping ratio.