Study On Measuring System Of Pyroelectric Material Under DC-biased Electric Field

The pyroelectric coefficient is a very important indicator to evaluate whether apyroelectric material is good or not. The Curie temperatures of phase-change pyroelectricmaterials such as （Ba，Sr）TiO3(BST),（Pb（Sc，Ta）O3,PST), etc, are near to theirworking temperatures. The capacities of these materials change greatly when thetemperature changes. Phase-change pyroelectric materials need to work under DC-biasedelectric field. So, it’s significant to design a measuring system which could accuratelymeasure the pyroelectric coefficient of phase-change pyroelectric materials underDC-biased electric field.According to the requirement of measuring pyroelectric material, in this thesis, thesamples worked under DC-biased electric field，and the pyroelectric coefficient wasmeasured by pyroelectric current method through stepped warming as a dynamictemperature-changing mode. Based on previous results and according to the analysis ofthe system requirement, this thesis made relevant changes and design for the hardwaresystem and the software system respectively and finally has designed a low costpyroelectric coefficient automatic measuring system which can be used under DC-biasedelectric field and measure the phase-change pyroelectic materials such as BST. In thedesign of hardware systems: since Phase-change materials need to be worked underDC-biased electric field, a DC-biased circuit was designed to add DC-biased voltage onsamples, and the pre-amplifying circuit is also re-designed. After that, the simulation andanalysis were done on the designed circuit by using Multisim software. In terms of thedesign of the software system, this thesis used computer feedback temperature controlalgorithm and Delphi software to program to achieve linear warming control and constanttemperature control.After the design of measuring system, we chose a series of related samples to test forrepeating times and compared them with the internationally recognized standards to verifythe measurement system. The results demonstrated that this system could reach thepractical level.