Ag-doped Lcmo Material Preparation And Liv Effect

LaAMnO (A=Ca,Ba,Sr,Pb) series materials have attracted a great deal of interest as a kind of important material that can be prepared as photodetector and magnetic electronic devices, because of the effect of CMR(Colossal Magnetoresistance). The investigation indicated that there is a import affect to the Tp of Ag-doped LCMO thin films epitaxialgrowth by Professor Zhang's group. However, there is no study deeply and systematively on the effect of the mechanism of Ag-doping and Ag addition on thermal-electric property of magnetic electronic devices.Ag doped La2/3Ca1/3MnO3 (LCMO:Agx) polycrystalline pellets, with x=0.00,0.01,0.05,0.10,0.20,0.30,0.40, which were prepared by solid-state reaction and Chemical co-precipitation method, were employed to fabricate LCMO:Agx epilayer on single crystalline LaAlO3 (100) substrate by Pulsed Laser Deposition technique. The experiment tends to investigate the influence of mechanism of Ag-doping and Ag addition to get the most perfect fabrication technology and addition which have corresponding with the best LIV effect. Meanwhile, to study the interaction mechanism between Ag-doping and LIV singnal. Series 1:solid-state reaction methodLCMO:Agx polycrystalline targets have been prepared by solid-phase sintering method. X-ray diffraction (XRD) patterns show that the samples have a pseudo-cubic perovskite structure.With the addition of Ag, there is a little change in a-axis and b-axis from x=0.00 to x=0.40. In addition,R-T curves demonstrate that the metal-insulation transition temperatures (Tp) increases sharply for x<0.05, and then increases slowly for x=0.05-0.40. The maximum Tp is 192 K, which is 80 K lower than that made by chemical coprecipitation method. This may be explained by the influence of powder grain size on Tp.LCMO:Agx epilayers have been fabricate on vicinal-cut single crystalline LaAlO3 (100) substrates by Pulsed Laser Deposition technique, meanwhile, the impact of growth conditions on fabrication of thin film were discussed.θ-2θX-ray diffraction and rocking cure analysis showed that all the films were c-oriented and presented good crystalline quality. The morphology of the as-grown films were detected by Atomic Force Microscope, and the results demonstrated that the surface roughness increased with increased Ag doping level, further, numerous laser droplets could be observed in all films. Laser induced voltage (LIV) effect was found in those films grown on the vicinal-cut LaAlO3 (100) substrates, with Ag content increasing, the peak value of LIV signal (Up) increased firstly and arrived to its maximum at x=0.05, then Up decreased up to x=0.10 and got its minimum at x=0.10, while Ag content dependence of response timeτof LIV signal just presented an opposite behavior. Series 2:Chemical co-precipitation methodLCMO:Agx polycrystalline targets have been prepared by Chemical co-precipitation metho. X-ray diffraction (XRD) patterns show that the samples have a pseudo-cubic perovskite structure. In addition, R-T curves demonstrate that the metal-insulation transition temperatures (Tp) increases up to 275K,with sharp TCR% as high as 28% when x=0.40,which has not been reported at home and abroad.The impact of growth conditions, growth temperature, laser energetic,laser frequency, Annealing oxygen pressure and annealing temperature, and the like, have been researched when fabrication of LCMO:Agx epilayers thin film on vicinal-cut single crystalline LaAlO3 (100) substrates by PLD technique.