Systematic research on RE2Zr2O7 (RE = La, Nd, Eu and Y) nanocrystals: Preparation, structure and photoluminescence characterization

A series of rare-earth zirconate RE2Zr2O7 nanocrystals (RE = La, Nd, Eu and Y) were prepared by a simple combustion method. These compounds possess either a pyrochlore structure (P-RE2Zr2O7) or a defect fluorite structure (F-RE2Zr2O7) which depends on the ionic radius of RE3+. The photoluminescence (PL) property of the as-prepared RE2Zr2O7 nanocrystals was studied, and the observed emissions in the UV and visible range were attributed to different transition mechanisms for RE2Zr2O7 with different RE ion. A PL mechanism has been proposed, associated with the transition between the valence band and a mid-gap state related to oxygen vacancies. Divalent Pb ions were introduced into RE2Zr2O7 nanocrystals and the luminescence of the Pb2+-doped samples was also recorded for comparison. The PL property of RE2Zr2O7 was found to be intimately related to their intrinsic defect structure, and PL was thought as a new method to estimate the degree of disorder in the A(2)B(2)O(7) structure (from pyrochlore structure to defect fluorite structure). (c) 2007 Elsevier Masson SAS. All rights reserved.