5322

4992

كارشناسي ارشد

ماده چگال

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1388

[ده]،99ص.:مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

هادي سلامتي

پرويز كاملي

13/4/89

جواد هاشمي فر، مهدي رنجبر

فيزيك

ID4992

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Preparation and investigation of structural magnetic and electrical properties of La0 85Ba0 15MnO3 manganite nanoparticles Student name Zahra Abedi Email address z abedi@ph iut ac ir Date of submission 1388 12 23 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Hadi Salamati salamati@cc iut ac irAbstractIn this thesis we report on the fabrication and the characterization of La0 85Ba0 15MnO3 LBMO nano crystal Thesamples have been prepared by sol gel and new solid state method Short time ball milling and non aqueous processare the advantage of this method In the first part of this project the effect of crystallite size on structural andmagnetic properties of La0 85Ba0 15MnO3 powders have been investigated The samples have been characterizedusing X ray diffraction and the average crystallite size of samples have been estimated by Scherrer formula Thestructural parameters and space groups have been obtained by FULLPROF soft ware Rietveld refinement It showsthat all the samples have Rombuhedral structure FE SEM and TEM images have shown that the magnitude of grainsize are in range of nanometer Susceptibility and transition temperature have been decreased by lowering ofcrystallite size The dynamic properties of sample has been prepared in temperature 620oC with new method hasbeen investigated by ac susceptibility for superparamagnetism Frequency dependence of blocking temperature hasbeen well described by Vogel Fulcher law The temperature dependence of the real and imaginary parts ofsusceptibility for a sample which as prepared by sol gel method in temperature 1350oC and revealed unusual andinteresting features which are associated with the domain walls and the effect of grain boundaries on theirmovements In the second part the effect of sintering temperature on structural magnetic and electrical properties ofLa0 85Ba0 15MnO3 have been investigated The structural parameters and space groups have been obtained byFULLPROF soft ware Rietveld refinement It shows that all samples have same structure as powder samples Magnetic susceptibility measurement showed that the susceptibility increases with increasing sintering temperature Magnetic susceptibility of bulk sample prepared at temperature 1350oC with sol gel method has been comparedwith powder sample of this method The results showed that in bulk sample the anomaly disappeared In order tostudy the transport properties of the samples temperature dependence of resistance have been measured Insulatorbehavior has been disappeared with increasing sintering temperature and metal insulator transition temperature hasbeen observed Samples resistance has decreased by increasing sintering temperature Kay words Nano manganite Crystallite size AC susceptibility Superparamagnetic Sinteringtemperature

هادي سلامتي

پرويز كاملي

جواد هاشمي فر، مهدي رنجبر