| The behavior of the excess oxygen in the K2NiF4-type structure has attracted much attention of researchers since superconductivity was found in La2CuO4+δ-based compounds. In La2CuO4+δthe excess oxygen remains mobile in low temperature and has a tendency to phase segregation into an oxygen-rich superconductive phase and oxygen-poor antiferromagnetic phase below the temperature of the phase separation. The structure and the properties were affected by the manner and characters of the excess oxygen, such as random or ordered distribution of over the interstitial sites, segregation or clustering, valence states, etc.La2NiO4+δwith the same structure of La2CuO4+δ, has served as a prototype in researching the behavior of the excess oxygen because it has greater capacity for absorbing excess oxygen compared to La2CuO4+δ. With increasing of excess oxygen, La2NiO4+δshows fruitful phenomena, such as phase separation, one-dimensional ordering and three-dimensional ordering, charge ordering and the magnetic order transition from the one-dimension to three-dimension and etc, which also have attracted much attentions. Pr2NiO4+δ, has the same structure as La2NiO4+δ, can absorb more excess oxygen than La2NiO4+δ, the phase transition of it changes from the orthorhombic phase to the tetragonal phase around 700K, and the phase-transition temperature is related with the content of excess oxygen. The state of the excess oxygen remains disordering in high temperature tetragonal phase and ordering in low temperature orthorhombic phase. The state of the excess oxygen still remains unclear in K2NiF4-type structure oxides and there are some discrepancies among the reported results; thus, whether the ordering of the excess oxygen really exists and to what extent the disorder in the arrangement of the excess oxygen atoms remains in the low-temperature phase in doped La2MO4+δ(M=Cu, Ni) system is an important issue. The internal friction technique, which in general measures the dissipation of elastic energy (Q-1), has proved to give valuable information about defects in ceramic samples. In the thesis we present the results of the internal friction study of a series of doped La2MO4+δ(M=Cu, Ni) samples and discuss the relation of the state of the excess oxygen and the internal friction spectra.The chapter 1 deals with the structure and the state of the excess oxygen in La2MO4+δ(M=Cu, Ni) system, and put forward what studied in the thesis. The chapter 2 deals with the theory of anelasticity, the methods used in the measurement, the standard anelastic solid and its dynamic properties as function of temperature, the theory of point-defect relaxations and the theory of the first-order phase transition, working principle of internal friction instrument, including the theory of iodometric titration and internal friction measurement.In chapter 3, we studied the low frequency internal friction and shear modulus of La2Cu1-xMxO4+δ(M=Zn, Li, Ni) system, the internal friction peak at 250K is due to the hopping of excess oxygen pairs. The excess oxygen transits from one-dimensional ordering to three-dimensional ordering with the excess oxygen increasing in Zn and Ni doped La2Cu1-xMxO4+δsystem. There is no evidence to approve that having three-dimensional ordering excess oxygen formation in La2Cu1-xLixO4+δsystem.In chapter 4, the low frequency internal friction and shear modulus of La2-xMxNixO4+δ(Pr, Nd, Sr) system. The glass freezing-in phenomenon of excess oxygen in La2-xPrxNiO4+δ(0≤x≤2.0) system is observed and discussed, the excess oxygen transits from one-dimensional ordering to three-dimensional ordering with the excess oxygen increasing, which also approved by the measurements of Pr2NiO4+δannealed in deferent atmospheres, there is only one relaxation internal friction peak in tetragonal phase La2-xPrxNiO4+δsystem while another peak exist in orthorhombic phase. The two internal friction peak also exist in Nd2NiO4+δsystem, and the first ordering phase transition internal friction peak appears in the system.The chapter 5 deals with the low frequency internal friction peaks and shear modulus of La2-xMxCuO4+δ(M=Nd, Pr, Sr) system. The structure phase transition internal friction peak was observed in La1.9Nd0.1CuO4+δ, and no relaxation internal friction peak appears in tetragonal phase of this system.
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