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 and795 °C, respectively without using any sintering aid. The dielectric constants (ε_r) 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.