Synthesis and characterisation of MoO3 and WO3 nanorods for low temperature co-fired ceramic and optical applications

Nanorods of MoO3 and WO3 are synthesized through a single step modified combustion process. The X-ray diffraction, Fourier transform Raman and infrared spectroscopy studies reveal that the as-prepared samples are phase pure, where MoO3 crystallizes in orthorhombic and WO3 in monoclinic structure. The transmission electron micrograph show elongated nano rods of the samples. The calculated optical band gaps of the samples suggest that these materials are semiconductors. The samples showed maximum transmission in the visible regions but poor transmittance in the ultraviolet region. The photoluminescence spectra recorded on the samples showed that WO3 has no visible luminescence, but exhibited strong ultraviolet emission whereas MoO3 showed blue emission. The MoO3 and WO3 samples are sintered to above 90 % relative density at temperatures 725 and 795 degrees C, respectively without using any sintering aid. The dielectric constants (er) of the sintered samples are 8 and 6 for MoO3 and WO3, respectively. The calculated temperature coefficient of dielectric constant is negative. The low sintering temperature, dielectric constant, low loss factor and negative temperature coefficient make the sample ideal for low temperature cofired ceramic, electronic substrate materials as well as suitable for various optical applications such as UV filters, transparent films for window layers on solar cells, anti-reflection coatings, scintillators, detectors.