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Silver Doping (Pr1-xLax)0.7Sr0.3MnO3(0≤x≤0.4)Polycrystalline Ceramic Preparation And Its Electrical Transport Properties

Posted on:2022-08-19Degree:MasterType:Thesis
Country:ChinaCandidate:X R PuFull Text:PDF
GTID:2511306554474824Subject:Materials science
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Strongly correlated manganese oxide Re1-xAexMnO3(Re is the Pr3+、La3+,and Ae is the Sr2+、Ba2+、Pb2+)is belong to a kink of rare earth-doped manganese oxides with a perovskite structure.Attributed to the excellent electrical properties,such as CMR effect,the Re1-xAexMnO3 have been studied by scientists.In recent years,the focus of more research has shifted to devices,such as spintronic devices,magnetic sensors and infrared bolometer(IR).The temperature coefficient of resistance(TCR)plays a key role in IR.Researchers have done much works on La-based manganese systems.The researchers have successfully solved the three major problems of Tk and Tp values far from room temperature,lower TCR values.Thus La AMnO3 is a candidate material for uncooled bolometer.However,the attention of electrical properties on Pr-based systems is less.According to the ferromagnetic phase diagram of Pr1-xSrxMnO3,it is known that the material has the strongest electromagnetic coupling at x=0.3.Thus,Pr0.7Sr0.3MnO3 is used as the base ratio.The La-doped or modulated Pr/Sr ratio to change its electromagnetic properties,so as to obtain the Pr system material with room temperature TCR value.Then Ag2O as the second phase composite to further improve the room temperature TCR value of the sample.Firstly,a series of(Pr1-xLax)0.7Sr0.3MnO3(x=0,0.10,0.20,0.25,0.30 and 0.40)polycrystalline ceramics were prepared.The resistivity gradually decreased with La content increased.The main peak of the crystal structure had a tendency to shift from single peak to double peaks.The Tp values gradually shifted toward the high temperature region.At x=0.25,the TCR value is 5.03%K-1 and Tk is 299.37 K,reaching the room temperature.Secondly,the(Pr0.75La0.25)0.7Sr0.3MnO3 material system with Tk and Tp reaching room temperature was selected,the Ag2O was doped by solid-phase method to prepare a series of(Pr0.75La0.25)0.7Sr0.3MnO3:Agx(x=0,0.05,0.1,0.15,0.2,0.25)composite materials.The results showed the crystal structure unchanged and the grain size increased.The resistivity decreased,while the Tp and Tk values remained almost unchanged.The Tk values remained at room temperature.TCR reaching the maximum value at x=0.15(11.35%K-1(Tk=300.69 K)).The effect of varying the Pr/Sr ratio on Pr1-xSrxMnO3(0.3≤x≤0.35)was investigated.At x=0.35,TCR value is 5.77%K-1(Tk is 298.63 K),reaching the room temperature.To further enhance the room-temperature TCR of PSMO ceramics and to analyze the mechanism of Ag2O doping mechanism,a series of Pr0.65Sr0.35MnO3:Agx(x=0,0.04,0.08,0.12,0.16 and 0.2)composite were prepared on the basis of Pr0.65Sr0.35MnO3.The results show that Ag2O is present in two forms,the main part is precipitated at the grain boundaries in the form of Ag,followed by a small part in the form of Ag+replacing Pr/Sr ions at the A-site.The addition of Ag2O does not change the crystal structure of Pr0.65Sr0.35MnO3.The TCR maximum value is 11.02%K-1 at x=0.16(Tk=300.05 K).In summary,the(Pr0.75La0.25)0.7Sr0.3MnO3:Ag0.15 and Pr0.65Sr0.35MnO3:Ag0.16 composite materials were achieved high room temperature TCR values(≥10%K-1,Tk=300 K).This result provides a reference for the application of Pr-based manganese oxide materials in advanced uncooled infrared bolometer and other optoelectronic fast devices.
Keywords/Search Tags:Sol-gel method, (Pr1-xLax)0.7Sr0.3MnO3:Agy, Pr1-xSrxMnO3:Agy, Temperature coefficient of resistance (TCR), The peak TCR temperature(T_k)
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