ZnO and Y-doped ZnO nanocrystalline films were separately fabricated on the glass substrates by sol-gel spin-coating method. X-ray diffraction patterns of the films show the same wurtzite hexagonal structure and (002) preferential orientation. SEM images show that grain size and thickness of the nanocrystalline films decrease with increasing doping concentration. The decrease of optical bandgap with the increase of Y doping is deduced from the transmittance spectra. Temperature-dependent resistivity reveals a semiconductor transport behavior for all ZnO and Y-doped ZnO nanocrystalline films. The resulting conductivity originates from the combination of thermal activation conduction and Mott variable range hopping (VRH) conduction. In the high temperature range, the temperature-dependent resistivity can be described by the Arrhenius equation, σ(T)=σ 0 exp[-(E a /kT)], which shows the thermal activation conduction. The activation energy E a increases from 0.47 meV for ZnO film to 0.83 meV for Zn 0.98 Y 0.02 O film. On the contrary, in the low temperature range, the temperature-dependent resistivity can be fitted well by the relationship, σ(T)=σ h0 exp[-(T 0 /T) 1/4 ], which indicates the behavior of Mott VRH. The results demonstrate that the crystallization and the corresponding carrier transport behavior of the ZnO and Y-doped ZnO nanocrystalline films are affected by Y doping.

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The effect of neodymium substitution on the lanthanum site in La 0.7−x Nd x Pb 0.3 MnO 3 perovskite polycrystalline has been systematically studied. The substitution of neodymium for lanthanum causes structure change from rhombohedral to orthorhombic. Ferromagnetism is suppressed as neodymium content increases. The magnetic order changes from a ferromagnetic long-range order with x = 0.0 to a spin-glass nature with x = 0.7. Besides, the ferromagnetic-paramagnetic transition temperature values are lower for the neodymium phases than for the lanthanum ones. Therefore, the introduction of neodymium degrades symmetry of the structure, diminishes the spin-coupling exchange interaction, and results in changes of magnetic properties. This fact is in good agreement with increasing the B value in Bloch's T 3/2 law and decreasing the spin-wave stiffness parameter D in quadratic dispersion relation.