Solid Photoacoustic Spectrum Detection Based On Piezoelectric Technique

The study on photoacoustic spectroscopy is one of the most active fields in recent years. As a non-destructive analytical method, this technology has characteristics of high sensitivity,strong pervasive,and can obtain space-resolved and time-resolved spectra at the same time. It has been wildly used in the areas of chemistry, physics, biology and medicine etc. It also can deal with those samples which are difficult to be detected by traditional analytical methods, like powders, thin films, opaque materials, amorphous materials and complex biological systems.In this thesis, the main works are design and build a high sensitivity photoacoustic piezoelectric (PAPZ) detection system composed by Ar+ laser as light source, Preamplifier Lock-in-Amplifier and oscilloscope as signal processing system; improved the conversion efficiency of photoacoustic signals, the anti-interference ability of the photoacoustic cell and the signal-to-noise ratio of system. Glass, thin films, liquid samples are measured by the PAPZ system, and the physical parameters such as Optical Transmittance, Optical Absorptivity, Concentration and so on are obtained. Using Mg-doped ZnO thin films prepared on glass substrates by radio frequency magnetron sputtering method, the optical absorptivity was measured by PZPA technique. The results were in a good agreement with the data obtained by the traditional spectrum method.The optical absorptivity of explosion-proof membrane using on car windows are also tested.The results were in a good agreement with the data already given. Based on Beer-Lambert Law, our PAPZ system can reach a very high sensitivity when measuring the concentration of the liquid samples by using subtraction method. The signals of photoacoustic and the concentration of pen ink solution were in a good linear relationship.This thesis also preliminary studied the auto-control and automatic signal acquisition program for the photoacoustic piezoelectric detection system.The advantages of applying VB and Lab VIEW languages to PAPZ system was analyzed, and the way of design,the flow chart of program was given.Lay a good foundation for improving the speed, the accuracy of detection and decreasing the experimental errors.