纳米BaTiO_3的光声光谱研究

Photoacoustic spectra studies of nanometer BaTiO_3

利用光声光谱技术对不同退火温度的纳米BaTiO3粉末进行了研究。结果表明，纳米BaTiO3粉末随晶粒长大，吸收边红移，说明能隙变窄，这与晶格参数变化有关．在橙黄光到近红外出现的宽吸收带是由氧缺位俘获的电子在缺陷附加能级上的跃迁所产生的，其变化趋势强烈地依赖于颗粒尺寸。

Photoacoustic spectroscopy has been used to study nanoscaled BaTiO3 powder with different annealing temperatures. The photoacoustic spectra show that the absorption edge of nanoscaled BaTiO3powder appears red shift with the increase of annealing temperature, which demonstrates that the energy gap becomes narrow. The decrease of energy gap is related to the growth of grains and the reduction of lattice parameters. In addition, an absorption band with several fine structures appear around 700 nm which is induced by the additional energy levels of oxygen vacancies and the transition of the captured electrons in the additional energy levels. Thus it is illustrated that the variation of the photoacoustic spectra strongly depends upon the grain sizes.