The neodymium chromate nanoparticles are synthesized by the sol–gel process. The phase formation with Pnma symmetry of the sample is confirmed by the Rietveld refinement of X-ray diffraction data. The particle size of the sample is determined by transmission electron microscopy. The band gap of the material is found to be 1.78 eV which is obtained by Tauc relation to UV-absorption spectrum. The room temperature Raman spectrum is fitted with the sum of 22 Lorentzian peaks. Dielectric relaxation of the sample has been investigated in the frequency range from 42 Hz to 1.1 MHz and in the temperature range from 303 to 573 K. The Cole–Cole model is used to explain the dielectric relaxation mechanism of the material. The complex impedance plane plot confirms the existence of the grain-boundary contribution to the relaxation of the sample. The frequency-dependent conductivity spectra follow the power law.

Dielectric relaxation and phonon modes of NdCrO 3 nanostructure

Orthorhombic structural perovskite NdCrO3 nanocrystals with size of 60 nm were prepared by microemulsion method, and characterized by XRD, TEM, HRTEM, SEM, EDS and BET. The catalytic effect of the NdCrO3 for thermal decomposition of ammonium perchlorate (AP) was investigated by DSC and TG-MS. The results revealed that the NdCrO3 nanoparticles had effective catalysis on the thermal decomposition of AP. Adding 2% of NdCrO3 nanoparticles to AP decreased the temperature of thermal decomposition by 87° and increased the heat of decomposition from 590 to 1073 J g−1. Gaseous products of thermal decomposition of AP were NH3, H2O, O2, HCl, N2O, NO, NO2 and Cl2. The mechanism of catalytic action was based on the presence of superoxide ion O2− on the surface of NdCrO3, and the difference of thermal decomposition of AP with 2% of NdCrO3 and pure AP was mainly caused by the different extent of oxidation of ammonium.

Preparation of NdCrO3 nanoparticles and their catalytic activity in the thermal decomposition of ammonium perchlorate by DSC/TG-MS

In this research, NdFeO3 orthoferrite nanoparticles (NPs) was synthesis by sol-gel combustion method. To investigate size effects on their structural, microstructural, magnetic and dielectric properties, the prepared samples were finally calcined at different temperatures. The analysis of X-Ray diffraction patterns show that the NdFeO3 NPs have orthorhombic structure with Pbnm space group without any impurity phase. To determine crystallite sizes and lattice strains, the Williamson-Hall (W H) method was used. The distribution of particles size according to FE-SEM images were calculated using a standard log-normal equation. The core-shell model was used to clarify the magnetisation behavior of NdFeO3 NPs and then the influence of particle size and lattice distortion on M − H hysteresis loop were discussed. The frequency dependence of relative dielectric constant and dielectric loss of NdFeO3 NPs have been investigated at room temperature.

M.C. Guillem

Papers

Preparation of mixed oxides MNdO3, with M=Cr, Fe. Comparison of several methods