Structral, Optical and Dielectric Characterization of Nanocrystalline AMo0.5W0.5O4 (where A=Ba,Sr and Ca) Prepared by Single Step Modified Combustion Technique

Abstract

Nanocrystalline AMo0.5W0.5O4 (A= Ba, Sr, Ca) have been synthesized through a modified combustion process. The X-ray diffraction studies have revealed that the samples are single phase and possess tetragonal structure. Raman spectra showed that the Ag modes of [MoO4]2− and [WO4]2− are split up into two well distinguished peaks while that of Bg and Eg modes of the tetrahedral units superimposed to form single strong peaks. Corresponding Au and Eu modes are registered in FTIR spectra. Vibrational analysis also confirms the long range order of lattice structure. The nanocyrstalline AMo0.5W0.5O4 are found to be excellent photo luminescent materials with strong blue and green emission. Blue emission is attributed to [WO4]2− and green emission responds to [MoO4]2− units. Thus we can fine tune the emission wavelength from blue to green region by varying the composition. These nanocrystals could be sintered at a relatively low temperature in the range 830-875oC for 3h to a high density. The SEM image of the sintered material indicates high densification of the material. The room temperature dielectric constant (ɛr) and of the sintered pellet at 5MHz were above ∼12 and attains a maximum value of ∼15. The low sintering temperature, moderate dielectric constant, low loss factor t makes nano AMo0.5W0.5O4 excellent composition for low temperature cofired ceramics, substrate material, and electronic packing materials, besides numerous optical applications.