Microstructure and dielectric properties of ion-doped La0.7Sr0.3MnO3 lossy ceramics at radio frequencies

Abstract

In this paper, the microstructure and dielectric properties of ion-doped La_0.7Sr_0.3MnO₃ are investigated in detail. The polycrystalline ceramics of La_0.7Sr_0.3Mn_1−yM_yO₃ (M = Fe, Ni, Cu; y = 0.3 or 0.5) are prepared by the sol–gel/sintering method. The symmetry of the crystal structure is improved and the dielectric properties obtained in the frequency range from 80 MHz to 1 GHz can be tuned by the doping of Fe, Ni, and Cu ions. With regard to the dielectric properties in lossy ceramics, the decrease of real permittivity ε^′_r for the doping of Fe and Ni will be effective for impedance-matching; the enhanced dielectric losses in the Ni and Cu doping samples will promote stronger absorption. Thus, the improved dielectric properties make ion-doped La_0.7Sr_0.3MnO₃ promising candidates for lossy ceramics in microwave electronics. In addition, the experimental results of permittivity were checked by K–K relations, and the frequency dispersion behaviors of the conductivity within a certain frequency range accord with the Jonscher's power law in the form of σ^′_ac(f) ∝ (2πf)ⁿ, demonstrating that the conductive mechanism is hopping conduction.