Electrical properties of lithium niobium borate glass containing erbium

A lithium niobium borate glass sample doped with erbium oxide was prepared by the quenching method. X-ray diffraction showed that the sample is in the glassy state. The difference between the crystallization temperature TT and the glass transition temperature T-g indicates that the addition of Er caused the sample to be more homogenized and therefore delayed the nucleation process. The electrical behaviour of the glass sample containing Er2O3 was investigated. The complex impedance data have been investigated by using the conductivity and the electric modulus formalisms. The effect of temperature on the dielectric modulus shows that the conductivity relaxation mechanism is temperature independent. The overlapping of the normalized peaks corresponds to the impedance and electric modulus and the identical values of thermal activation energy occurring in the present glasses. The thermal variation of resistance showed an insulator to metal transition peak and it was observed that the T-MIT for the sample is lower than the transition temperature of sample free from the rare earth. The values of the frequency exponent S are dependent on both frequency and temperature, which agrees with the overlapping large polaron tunnelling (OLPT) model. The activation energy associated with the electrical relaxation determined from the electric modulus spectroscopy was found to be close to the activation energy of a.c. conductivity at high frequency indicating thus the same effect in both processes.