Synthesis, phase-formation, IR and terahertz spectroscopy of bulk-InGaZnO4 obtained by metal-nitrate-glycol gel decomposition method

In this work, nanosized InGaZnO4 ceramics were obtained by metal-nitrate-glycol gel decomposition method. It was found that this method can produce a material with varying different of crystallinity (from amorphous to highly crystalline) as a result of sintering at different temperatures (500 … 900°С) without any crystalline impurities. The XRD method was used to study the kinetic patterns of particle growth. Isothermal and non-isothermal conditions of particle growth were studied. The activation energy of the InGaZnO4 crystallite growth process was calculated at low and high sintering times. SEM and TEM methods were also used to determine the morphology and crystallinity states of samples sintered at different temperatures. The EDS data confirm the homogeneous distribution of elements and the absence of amorphous agglomerates (impurities) in the material. The optical energy gap of InGaZnO4 was calculated from UV–vis spectroscopy data. In order to study the effect of crystallites size on the infrared-active excitations, room-temperature terahertz-infrared (frequencies 4-3500 cm−1) spectra of a series of ceramic samples with different crystallites size have been measured. 17 infrared absorption lines are observed and assigned to phonon and interatomic bonds vibrations. The parameters (frequency, damping, intensity) of the lines are found to be strongly dependent on the sintering temperature and thus on the crystallites size. The obtained data may be useful for further production of IGZO-based inks.