Simulation Of Positron Implantation In Metals And Study About Lead Titanate Related Materials

The wide range applications of positron annihilation spectroscopy in the fields of particle and nuclear physics,medicine,chemistry,material science and biology promote the development of positron science.The studies of this dissertation focus on two main parts.For the first part,the processes of positron beam implantation in metals are studied by employing the GEANT4 software.Our work makes us know more about the behaviors of positron in materials.For the second part,positron annihilation lifetime spectrum(PALS)with other necessary assistant measurements was used to measure the microstructure of PbTi03 and its relatives.We want to find out the influences on the ferromagnetism of materials.The details are shown as follows:1.Simulation of Positron Implantation in MetalsBy using the GEANT4 software,we design the suitable geometric structure,choose the right physical model and use the accurate data acquisition system.The simulation of positron implanting into metals is carried out at normal incidence and oblique incidence.In order to prove the correctness of simulation,simulated data are compared with experimental data.Then,three-dimensional coordinate is introduced to study the depth distribution.We find out the deviation of center of depth distribution under oblique incidence and analyze the causes of deviation.Our study does not only show the details about behaviors of positron in materials,but also provides reference data for the study of transverse motion of positron in materials.2.The Study on Ferromagnetism of PbTi03 and its Relatives Using Positron Annihilation Lifetime SpectrumThe PbTi03(PTO)are prepared by a conventional solid-state process.We amend the processing method and calcination temperature and finally get PbTi03 and its relatives.After using X-ray diffraction to test materials and proving the correctness,we think that intensity of Pb related vacancies increases due to the doping of La by PALS.We combine the results of magnetic measurement and differential scanning calorimeter with PALS and find that the ferromagnetism of PTO disappears after La doped.At last,we explain the disappearance of ferromagnetism with PALS.