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The features of High-k hollandite-like ceramics doping by copper

Abstract

Holland-like complex oxides Ax(Ti,M)8O16 (A is a non-framework cation and M is a transition metal substituting for Ti4+ in the framework) are characterized with high polarizability due to mobility of alkaline ions,  incorporated into the 1-D channels, and variable valence of the transition metals.These structural features allows considering hollandite-like solid solutions as alternatives to the non-ferroelectric perovskite-like Ceramic materials (CaCu3Ti4O12 and Ba(Fe0.5Nb0.5)O3) exhibiting high (ε~104) values of the dielectric constant in a wide temperature and frequency ranges. However, the traditional methods used to produce the hollandite-like solid solutions are complicated. In this report, we present a two-stage technology for the synthesis of hollandites in the K2O-CuO-TiO2 system. This methodology is based on a use of the amorphous potassium polytitanate, modified in aqueous solutions of copper salts as a precursor material.A presence of well-developed internal surface of layered PPT flakes allows introducing the transition metal ions directly into the structure of the precursor material. The optimal experimental conditions of the chemical treatment (pH, concentration of the aqueous solution, PPT doses) as well as the following thermal treatment (thermal regimes) which allow producing copper-containing hollandite-like potassium titanates were determined. In this regard, the method to produce sintered at 1000-1100 °C ceramics based on hollandite-like powdered solid solutions was proposed and the electric properties of the obtained ceramic specimens were investigated in the frequency range from 1 MHz to 0.1 Hz. The dielectric constant and tangent of dielectric losses for the ceramic samples calcined at 1075 °C were of 104-105 and 0.2-0.9, respectively.The synthesized material can be used as for the production of ceramic dielectrics as high-k ceramics filled polymer-matrix functional composites.This research was financially supported by the Russian Science Foundation (project № 19-73-10133).

 Nikolay Gorshkov

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