Characterization, dielectric and optical studies of cerium molybdo tungstate nanoparticles

Nanoparticles of cerium molybdo tungstate (CMT) have been prepared by chemical co-precipitation method. The average particle size is determined from X-ray diffraction studies. The nanoparticle nature of the sample is verified using SEM, TEM and AFM images. The surface morphology of the sample is studied from SEM image. The FTIR spectrum has been used to study the stretching and bending frequencies of molecular groups in the sample. Temperature and frequency dependence of the dielectric constant and ac electrical conductivity have been investigated. The dielectric permittivities of the samples are evaluated from the observed capacitance values in the frequency range 100 Hz - 1 MHz and in the temperature range 50 deg - 110 deg C. It has been found that with increasing frequency, the dielectric constant decreases. The high value of dielectric constant at low frequencies may mainly be due to the space charge and rotational polarization. Also, the dielectric constant increases with increase in temperature for fixed frequencies. As the temperature increases more and more dipoles will be oriented resulting in an increase in molecular dipole moment. The ac electrical conductivity is evaluated from the permittivity studies. The absorption spectra of the sample in the UV range are recorded. From the analysis of the absorption spectra, the material is found to have a direct band gap of 3.2 eV. (author)