Electrochemical characterization of sodium and potassium doped lanthanum-titanium mixed oxides prepared by sol-gel method

摘要

Varying amounts of Na and K doped lanthanum-titanium oxides were synthesized by gel entrapment technique. These ceramics were characterized by X-ray diffraction. Microstructural investigations revealed grain growth in the doped material compared to undoped sample. Dielectric relaxations of these compounds were investigated in the temperature range 250-900 A degrees C. A high degree of dispersion of the permittivity of un-doped lanthanum-titanium oxide and K and Na doped lanthanum-titanium oxide was observed in the frequency range < 100 kHz which was attributed to oxygen vacancies. An increase in the permittivity values were observed with 1 % Na and K doped samples. The permittivity values further deteriorated with the dopant concentration. Using the Cole-Cole model, an analysis of the dielectric loss with frequency was performed, assuming a distribution of relaxation time. The dielectric loss was found to decrease by doping K in lanthanum-titanium oxide matrix. The dc conductivity studies showed that a temperature dependent hopping type mechanism is responsible for electrical conduction in the system.