Local levels in La_(1-x)Sr_xScO_(3-x/2) band-gap under interaction with components of O_2, H_2, H_2O atmospheres

摘要

The paper studies the electronic structure of proton-conducting oxides based on the lanthanum scandate La1-xSrxScO3-x/2 for advancing in understanding the mechanisms of hydrogen uptake from dry and humid atmospheres into the lattice of oxides with a perovskite structure. The process of protons incorporation from H2O containing atmospheres is considered to describe by the reaction H2O + O-o(x) + V-o(center dot center dot) = 2OH(o)(center dot). However, there is no established concept of a mechanism for proton uptake from a dry H2 atmosphere. At such an uptake, a positively charged proton defect will be formed in the oxide lattice, and a negative charge must appear for compensation of the excess positive charge. Formally, the reaction of this process can be represented as 1/2H(2) + O-o(x) = OHo center dot + e'. In this case an uncompensated electron appears, and the question arises as to where it is localized. In order to answer this question, it is necessary to study the electronic structure of perovskites.