Preparation And Properties Study Of PMNT Pyroelectric Infrared Sensor Materaials

Lead based relaxor complex Perovskite strueture ferroelectrics of Lead Magnesium Niobate-Lead Titanate (l-x)PbMg_l/3Nb_2/3O₃-xPbTiO₃(PMNT),a solid solution system of B-site ions complex to replace(ABO3) perovskite structure, Widely used in microelectronic as its remarkable dielectric and electrostrieve properties. The trend leads to the R&D preparation and the applications of relaxor ferroelectric materials, for the rapid development of today's electronics and information field. The relaxor ferroelectric ceramics research cause more and more attention due to it comparable with the performance of single-crystal and the difficulties in single-crystal growth, high cost of thin-films.PMNT ceramics with complex perovskite structure had been obtained successfully with inorganic-sol-gel method in this paper, The processing conditions, including the composition content, calcinations temperature and holding time, had been discussed. the causes of the pyrochlore phase was summarized. Furthermore, we try to contrast complex perovskite structure PMN-PT to the solid-phase ball milling method, two-step synthesis method and co-precipitation synthesis method.The appropriate pre-burn time, pre-sintering temperature, heating rate on calcination conditions was determined by the materials measured adopt Differential thermal analysis (DTA).X-ray Powder diffraction (XRD) was adopted in structure and Phase analysis to determined the appropriate composition content for the PMN-PT system. Using scanning electron microscopy (SEM) observation of the grain morphology. And also the dielectric constant and dielectric loss of the ceramics was researched. The research results obtained are as follows:1. To soluble inorganic salt as raw material, ethylene glycol as solvent, were successfully prepared by citric acid as the chelating agent containing Pb, Mg, Nb and Ti metal ion complex precursor solution (calculated as Pb-Mg-Nb-Ti-CA ). Experiments show that the technology in the preparation of the ceramic has a simple process, low cost, and advantages such as repeatability, very suitable for the preparation of ceramic powders. 2. By DTA analysis identified pre-sintering temperature of 500℃, the pre-burn time of 5h, the final calcination temperature of 1150℃baking time is 2h. SEM from the combined results of XRD analysis shows that using the above-gel precursor solution prepared by the 1150℃was almost entirely perovskite phase, and have good dispersion, the high reactivity of the various components of the PMNT powder, Perovskite phase to 99.4%. The ceramic has nice density after sintering, d33 to 330 pC / N, the pyroelectric coefficient to 5.5×10^-8C.cm^-2.K^-1.3. This paper discussed in depth the impact of ceramics prepared by various factors, including the main research results summarized in:(1)Pyrochlore phase can be effectively inhibited by excess Pb, the production of raw materials during the preparation of effective control of the ratio of Pb is conducive to the formation of the whole structure of the PMNT perovskite powder.(2)The drying process to ensure the stability of the temperature between 130℃-150℃and then, if the temperature change is too large, may lead to gel heterogeneity.(3) In the pre-burn process, to ensure the complete pre-gel burning all of its organic matter removed. Until the gel from the dark brown into orange.(4) In the roasting process, must be stamped in the sintering of alumina crucible, because at high temperatures the volatilization of Pb in PMNT will affect ceramic components, the final ceramic performance from a very big impact, and in the stamping of the alumina crucible sintering can reduce the volatilization of Pb, the basic components to ensure stability.Use of such inorganic sol-gel method was successfully prepared the various components of PMNT powder. We can be expected: This technique can be extended to other multi-component applications and preparation of complex oxide powders to the process.