The Study Of Material Optical And Thermal Characteristics Based On Piezoelectric Photoacoustic Technique

Because of the advantages of high sensitivity and wide range detection spectrum,Photoacoustic spectroscopy has been widely applied in physics, chemistry, biology, medicine,chemical industry, environmental protection, materials science and the other fields.Photoacoustic spectroscopy can provide the information of photoacoustic amplitude andphase, it has great advantage in analyzing Stratified sample, especially the thin film.In this thesis, The properties of thin film materials and liquid were measured based onthe photoacoustic spectral detection system, It completed the study of optical and thermalcharacteristics such as sample absorptivity, thermal diffusivity and the concentration of thesolution.The optical absorption characteristic of ITO thin film is studied in optical light. Theresults are in a good agreement with the data obtained by the CDIR thin film analysis systemNKD8000. Experiments prove that the optical absorption rate of the ITO film non-linearlychanges with the wavelength in the visible light range, Nearby450nm, the absorption is thestrongest, and the absorption decrease gradually along with the increase of the wavelength, in514.7nm place, it is close to zero, then increase slowly.The thermal diffusivity rates of8different thickness SrTiO₃films are measured based onthe back excitation photoacoustic technology, the variety of photoacoustic signal amplitude,phase and the thermal diffusion rate with the film thickness is studied, it is found that:photoacoustic signal amplitude and phase gradually decrease with the film thickness; butalong with the increase of the thickness, the thermal diffusion rate of the thin film firstincreases, then decreases, and in a certain thickness, the thermal diffusion rate reaches itsmaximum. On the condition of the same thickness, the research on the relativity between thephotoacoustic signal amplitude, phase, film thermal diffusivity rate and the modulationfrequency shows that: photoacoustic signal amplitude and phase non-linearly decrease withthe increasing of frequency, but the thermal diffusivity rates of the thin film are stable.The relationship between photoacoustic signal intensity and concentration of honey andNaCl solution was investigated by piezoelectric technique, The results show that thephotoacoustic signal intensity of the low concentration honey solution changesnon-monotonic along with the increase of the concentration, and in a certain concentration,the signal intensity reaches its maximum; the photoacoustic signal intensity of the NaClsolution adds linearly along with the increase of the concentration. Meanwhile, by Lambert-Beer law, using the standard curve method, the concentration of the NaCldeterminand solution was measured according to the concentration of NaCl standard solution,and it provides a basis to analyzing the solution concentration and composition.