Effect of A Site and Oxygen Vacancies on the Structural and Electronic Properties of Lead-Free KTa0.5Nb0.5O3 Crystal

Abstract

The structural and electronic properties of lead-free potassium tantalite niobate KTa0.5Nb0.5O3 (KTN) with A site vacancies \( V_{\rm{K}}^{0} \), \( V_{\rm{K}}^{1 - } \) and oxygen vacancies \( V_{\rm{O}}^{0} \), \( V_{\rm{O}}^{2 + } \), were investigated by first-principles calculations, which indicated that A site vacancies \( V_{\rm{K}}^{0} \) are likely to form in the KTN compared with \( V_{\rm{K}}^{1 - } \) , and oxygen vacancies \( V_{\rm{O}}^{2 + } \) are likely to form compared with \( V_{\rm{O}}^{0} \) in the KTN according to the investigation of formation energy. The results show that K and O vacancies have significant influence on the atomic interactions of the atoms and the electronic performance of the materials. And Ta atoms are more easily influenced by the K and O vacancies than the Nb atoms from the atomic displacements in KTN with K and O vacancies. The investigation of density of state indicates that the compensation of electrons in KTN with vacancies make the hybridization become stronger among Ta d, Nb d and O p orbitals. Besides, Mulliken population of all the Ta and Nb atoms in KTN with charged vacancies are influenced by complement electrons. The strength of the Nb-O bond is stronger than Ta-O based on the changes of bond lengths and Mulliken population.