Enhanced negative permittivity by A-site heterovalent-ion doping in La1-x-yCaxKyMnO3 perovskite

Abstract

Adjusting the concentration of free carriers is a direct strategies to attain an ideal negative permittivity. Employing chemical methods for atypical ion doping is an effective way to regulate the concentration of free carriers. Due to the A-site tunability of perovskite manganese oxides, doping with multiple valent ions becomes particularly favorable. In this study, to realize temperature-stable negative permittivity, mono-phase La1-x-yCaxKyMnO3 (named LCKMO) perovskite crystals with diverse compositions are prepared, using a ultra-high alkaline hydrothermal method. Heterovalent ion doping (La3+, Ca2+, K+) at the A-site within the perovskite crystal structure occurred with the aid of the disproportionation reaction of Mn ions at the B-site during the extreme hydrothermal conditions. By adjusting the La/Ca ratio, we are able to vary the doping content of K+. Experimental findings reveal that as the concentration of K+ increases, so does the concentration of Mn oxide states, suggesting the presence of additional free carriers resulting in a more negative permittivity and minimized dielectric loss. This work pioneers a novel synthetic pathway for the creation and design of negative permittivity materials.