Disorders and oxygen vacancies in p‐type Sn 2 B 2 O 7 (B = Nb, Ta): Role of the B‐site element

Sn 2 Nb 2− x Ta x O 7 ( x = 0.0–2.0) with pyrochlore structure is a promising material for p‐type oxide semiconductors. A systematic study of its Nb/Ta ratio indicated that the hole–generation efficiency of the Nb end (Sn 2 Nb 2 O 7 ) was an order of magnitude lower than that of the Ta end (Sn 2 Ta 2 O 7 ). Although this occurs due to differences in oxygen‐vacancy formation, the origins of the hole–generation efficiencies remain unclear due to limited information on local and global crystal‐structure disorders in pyrochlore Sn 2 Nb 2 O 7 and Sn 2 Ta 2 O 7 . In this study, the crystal structures of Sn 2 B 2 O 7 (B = Nb, Ta), composed of BO 6 octahedra and Sn 4 O tetrahedra, were investigated using X‐ray absorption spectroscopy and X‐ray diffraction. A detailed investigation of the local and global crystal structures indicated a larger amount of disorder in the Sn 4 O tetrahedra in Sn 2 Nb 2 O 7 compared to Sn 2 Ta 2 O 7 ; disorder in the BO 6 octahedra occurred only in Sn 2 Ta 2 O 7 . This study indicates that an appropriate selection of the B‐site element is vital for suppressing defect and disorder formation in Sn 4 O tetrahedra and subsequently improving the hole–carrier–generation efficiency.