ELECTRONIC STATES DENSITY, RESISTIVITY, AND PHASE COMPOSITION OF CaTiO3 PEROVSKITE WITH ISOMORPHIC IMPURITY OF NIOBIUM

Abstract

The application of materials with a perovskite structure has currently become one of the most promising approaches for the development of photovoltaic systems. A method for high-speed synthesis (under 15 minutes) of CaTiO3 perovskite — TiO2 rutile with the possibility of concurrent doping of the product has been developed. The density of electronic states, phase composition features, and resistivity of niobium-doped perovskite (CaTiO3) were investigated. The calculations of the density of electronic states for niobium-doped CaTiO3 have shown that at low concentrations of niobium, the samples exhibit conductivity characteristic of semiconductors. Since niobium has one more valence electron compared to titanium, as the niobium content increases, the Fermi level shifts to the band of free states. This shift of the Fermi level should lead to a change in the nature of the conductivity of doped crystals, eventually transitioning to metallic conductivity at high concentrations of niobium. Composite analysis (СаТіО3+ТіО2) by X-ray diffraction has shown that the use of niobium as a doping element significantly accelerates the CaTiO3 synthesis reaction, and increases the perovskite concentration in the sample. The concentration of CaTiO3 in the sample the with niobium is 83 % vol. at a temperature of 900ºC and at a synthesis time of 5 min, whereas when using a mixture without Nb, the content of perovskite will be only 58 % vol. at a synthesis time of 12 min. X-ray phase analysis methods confirm the formation of a solid solution (doping) Ca(Ti,Nb)O3, resulting in the preparation of samples (СаТіО3+ТіО2) with resistivity inherent to semiconductors.