Doping dependent high-frequency dielectric properties of Hf1-xTixO2 nanoparticles

High-frequency dielectric properties of Ti-doped HfO2 (Hf1-xTixO2 (x= 0-0.5)) nanoparticles at room temperature were reported. The Hf1-xTixO2 nanoparticles were developed by a facile chemical synthesis process. Structural and morphological properties of the derived samples were analyzed with X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). The derived samples show well dispersed particles of 5-10 nm size depending on the heat treatment temperature during synthesis. XRD studies revealed the complete amorphization in the HfO2 crystal structure with the increase in Ti doping. Impedance spectroscopy studies were performed in pelletized samples in the frequency range of 1 MHz to 1 GHz. The real and imaginary parts of dielectric constant show rapid decrease with the increase in frequency in all the samples. The Nyquist plots of the complex impedance suggest that the grain boundary contribution predominates in the conduction mechanism in the derived samples. The ac-conductivity in the samples increases with the increase in frequency irrespective of Ti concentration and shows significant drop with the increase in Ti concentration at all frequencies.The obtained results were analyzed in correlation with microstructure and doping concentration in the derived samples.