| A2M3O12(A=a trivalent transition metal or a lanthanide from Lu to Ho, M=W6+ or Mo6+) type of material, including two kinds of crystal:monoclinic and orthorhombic structure. A2M3O12 with orthorhombic structure has a microporous structure, open structure, therefore, such materials exhibit unusually high trivalent ionic conductivity [1-5].Because of these features these materials have broad application in fuel cell electrolyte [6], gas detectors [7-8] etc. In recent years, the finding of these compounds'negative thermal expansion property in three crystals [9], and a larger sized A cation causes the stronger NTE [10]. Mary et al. [11] demonstrated that the engineering of the thermal expansion coefficient is possible through partial substitiution of the A cation by some other trivalent cation, such as Al1.68In0.3Sc0.02W3O12, Al1.7In0.3W3O12 etc. Because of these property, they are useful in optical, opto-electronics and other fields [8,12-15].In A2M3O12 family with orthorhombic structure, yttrium(Y) has the largest ionic radius and show strongest negative thermal expansion in a very wide range of temperature (from room temperature to 1173K), and in this temperature range it does not occur within the phase transition. Y2Mo3O12 is the material with the biggest negative thermal expansion coefficient [13,16], and linear expansion coefficient is up to -9.36×10-6/K (αa=-11.69×10-6/K,αb=-6.57×10-6/K,αc=-10.04×10-6/K) [9-10]. Nassua [17] and T. A. Tunik [18] produced orthorhombic structure Y2Mo3O12 materials in the first time, and its basic properties were studied. Liang et al [16,19] prepared orthorhombic structure Y2Mo3O12 materials using laser rapid sintering and studied the effect of water molecules in the orthorhombic structure Y2Mo3O12 phonon pattern.Compared with bulk materials, thin film has a larger surface area and a special surface structure, which will cause new features [20] and have great potential for applications [21], to create efficient bimorph actuators with two different expansion coefficient of the films, to use low-expansion or negative thermal expansion materials instead of compensatorsn in some structures which must maintain their shape etc.Therefore, the study of lower or negative thermal expansion films are very important.In this paper, Y2Mo3O12 polyrystalline ceramic target synthesized by solid-state reaction and Y2Mo3O12 thin films were prepared by magnetron sputtering method. They were charactered by scanning electron microscope, X-ray diffraction, temperature dependent Raman spectra, UV-vis spectroscopy,Y2Mo3O12 film, using SEM, XRD, variable temperature Raman spectroscopy, UV-vis spectrophotometer, spectroscopic ellipsometer and so on. The preparation technics of Y2Mo3O12 polyrystalline ceramic target and Y2Mo3O12 thin films were studied. The effect of sputtering time and different substrate on Y2Mo3O12 thin films were studied. The main results were following:(1) The orthorhombic structure Y2Mo3O12 (ICDD-JCODS-PDF No 28-1451) polyrystalline ceramic target were prepared by solid-phase sintering, space group pbcn.(2) The orthorhombic structure Y2Mo3O12 thin films can be perepared with By magnetron sputtering method. The optimum conditions are:workpiece rotaing speed 60 rpm, substrate temperature 200℃, sputtering gas pressure 1.3 Pa, sputtering power 200W.(3) Propriate annealing could improve the crystal structure of the Y2Mo3O12 thin films. The unannealed Y2Mo3O12 thin films were amorphous. After unannealed Y2Mo3O12 thin films crystallization. It was found that:Annealing in 800℃for 3 hours is the best heat treatment conditions.(4) The absorbency of Y2Mo3O12 thin films have been analyzed by the temperature dependence of Raman spectroscopic for the first time. Y2Mo3O12 thin films have reerisible dehydration.(5) The film has an optical bandgap width of 4.58 eV and a high absorbency for near-ultravillet. Therefore, it could be applied to solar-blind detector.(6) The Current-voltage characteristics of the Y2Mo3O12 thin film show non-linear relationship and is the characteristics of the semiconductor conductivity.
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