Effect of erbium substitution on thermoelectric properties of complex oxide Ca_3Co_2O_6 at high temperatures

Polycrystalline particles of Ca3-xErxCo2O6 （x=0.0, 0.15, 0.3, 0.45 and 0.6） were synthesized using sol-gel method combined with Low Temperature Sintering procedure （LTS） to evaluate the effect of Er substitution on the thermoelectric properties of Ca3Co2O6. The crystal structure and microstructure were investigated using X-ray diffraction, infrared spectroscopy and scanning electron microscope. The electrical conductivity and Seebeck coefficient of the complex oxides were measured from 300 to 1073 K. The results showed that all the sampies were p-type semiconductors. The electrical conductivity increased with the increase in temperature. Er substitutions at Ca site affected carrier concentrations and carder mobility, resulting an increase in Seebeck coefficient and decrease in electrical conductivity. The power factor of Ca2.85Er0.15Co2O6 reached 10.66 μw/mK^2 at 1073 K.

Influence of the substitution of Sm, Gd, and Dy for La in La_(0.7)Sr_(0.3)MnO_3 on its magnetic and electric properties and strengthening effect on room-temperature CMR

A series of La0.7-xSmxSr0.3MnO3, La0.7-xGdxSr0.3MnO3, and La0.7-xDyxSr0.3MnO3 （x=0.00, 0.10, 0.20, 0.30） samples were prepared by the solid-state reaction method. The influence of the substitution of Sm, Gd, and Dy for La on the magnetic and electric properties and on the magnetoresistance （MR） was studied through measurements of M-T curves and p-T curves. The results showed that： lattice distortion induced by substitution of Sm, Gd, and Dy for La and extra magnetism of substitution had great influence on the magnetic and electric properties of pcrovskite manganites; substitution of magnetic rare earth element for La was an effective way to change Curie temperature and to strengthen MR in perovskite manganites; and appropriate substitution proportion would generate large MR near room temperature.

Effects of lanthanum substitution on microstructures and intrinsic magnetic properties of Nd-Fe-B alloy

（Ndl-xLax）30Fe69B （x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6） alloys were prepared by inducting melting, and the effect of substitution of La for Nd on their microstructure and intrinsic magnetic properties were investigated. With the increase of La content, Curie tem- perature （Tc） decreased from 582.4 to 557.4 K, saturation magnetization （Ms） decreased from 1.59 to 1.37 T, and anisotropy field （HA） decreased from 5394 to 3911 kA/m. However, the reductions of the intrinsic magnetic properties were relatively gentle as La content increased, which meant that the intrinsic magnetic properties still had the potential to fabricate permanent magnets. Moreover, further microstructure observations showed that La tended to diffuse into the Nd-rich grain boundary phase instead of main phase during the substitute process. Such aggregation behavior was beneficial to fabricating La containing magnet with high Ms.

Structural,morphological and magnetic properties of(Ni_(0.5)Co_(0.5))[Ga_(x)Gd_(x)Fe_(2-2x)]O_(4)nanoparticles prepared via sonochemical approach

The impact of Ga^(3+)and Gd^(3+)co-substitution on different types of behavior of Ni-Co nanospinel ferrites(NSFs),(Ni_(0.5)Co_(0.5))[Ga_(x)Gd_(x)Fe_(2-2x)]O_(4)(0.000≤x≤0.025),was investigated.NSFs were fabricated through ultrasound irradiation.The structure,composition,and spherical morphology of all products were verified by numerous characterization techniques such as X-ray diffraction(XRD),scanning and transmission electron microscopes(SEM and TEM),and selected area electron diffraction(SAED).Mossbauer spectra are composed of two ferromagnetic sextets and one paramagnetic doublet.These spectra were fitted to extract hyperfine parameters of the doped samples.Both sublattices'hyperfine magnetic field decreases with substitution.The isomer shift values show that the Mossbauer spectra are composed of magnetic Fe^(3+)sextets.The magnetization measurements at variable magnetic field(M-H)were investigated via a vibrating sample magnetometer(VSM)at temperatures(T)from 300 to 10 K.All NSFs disclose ferrimagnetic behavior at both 300 and 10 K at which they are soft and hard,respectively.We determined that the remanence magnetization(M_(r)),saturation magnetization(M_(s)),and magneton number(n_(B))decrease with increasing Ga^(3+)and Gd^(3+)ions contents.The reduction in these values is predominantly recognized to be the impact of cation redistribution and surface spins on tetrahedral(T_(d))and octahedral(O_(h))sites.As the Ga^(3+)and Gd^(3+)contents increase,the coercivity(H_(c))is also found to decrease.

Thermal and transport properties of La_(2–x)Nd_xMo_2O_9

Single-phase La_（2–x）Nd_xMo_2O_9（0≤x≤1.8） compounds were prepared using solid-state reaction technique. Their structural and thermal p roperties were characterized by room and high temperatures X-ray diffraction（XRD）, thermo gravimetric analysis-differential scanningcalorimetry（TG-DSC）, and high temperature Raman spectra. The transport properties were investigated using D.C. four-probe technique and Hebb-Wagner polarization method. The substitution limit of Nb^（3＋） in La_（2–x）Nd_xMo_2O_9 was determined to be in the range of 1.8