Preparation, Characterization, Photocatalytic Activity and Conductivity Studies of YLnTi₂O₇(Ln = Nd, Sm, Eu and Gd)

Abstract

IntroductionTernary oxides with general formula A 2 B 2 O 7 or A 2 B 2 O 6 O are isostructural to the mineral pyrochlore, (NaCa)(NbTa)O 6 F/OH. 1 Eight coordinate A site can be occupied by trivalent lanthanides, divalent alkaline earth or monovalent alkali ions. Site B can be filled by six coordinate tetravalent (Ti 4+ , Zr 4+ , Hf 4+ and Sn 4+ ) or pentavalent (Nb 5+ and Ta 5+ ) ions for charge neutrality. These materials have received considerable attention for their remarkable properties and potential applications. These oxides possess high oxygen ion conductivity, 2, 3 excellent microwave dielectric characteristics, 4 optical nonlinearity, 5 high radiation tolerance, 6 magneto-resistance, superconductivity, 7, 8 high chemical stability, high refractive index and good catalytic activity. 9-12 They are used as sensors, transistors, 9 thermal barrier coatings, 13, 14 fast ion conductors, 1, 15 high permittivity dielectrics, 14 electrocatalysts 16 and for nuclear waste encapsulation. 17 The structure of pyrochlore is characterized by corner sharing of BO 6 octahedra forming a B 2 O 6 network which intersects with A-O chains of formula A 2 O. 1 The oxide ions occupy seven-eighth of the tetrahedral sites between the cations. These materials crystallize in cubic lattice with Fd3m space group (Z = 8). The pyrochlore structure is considered as super structure of fluorite, AO 2 (Fm3m, Z = 4) but with ordered cations and ordered vacancies in one-eighth of the tetrahedral oxide ion sites. 18,19 The lattice constant of pyrochlore is twice to that of fluorite. The A

The Fabrication and Property Characterization of a Ho2YSbO7/Bi2MoO6 Heterojunction Photocatalyst and the Application of the Photodegradation of Diuron under Visible Light Irradiation

“…Previous studies have demonstrated the favorable photocatalytic capability of A 2 B 2 O 7 and AB 2 O 6 mixtures under visible light exposure (VLE) [33][34][35][36][37][38][39]. For instance, Devi et al achieved a photocatalytic removal efficiency (REF) of 66% for methylene blue (0.1 mmol/L) using the photocatalyst YGdTi 2 O 7 under VLE for 180 min [40]. Similarly, Zhang et al reported an REF of 69.7% for methyl orange (20 mg/L) using the photocatalyst Gd 2 Ce 2 O 7 powder under VLE for 300 min [41].…”

Synthesis, Characterization of Dy2NdSbO7/Bi2WO6 Heterojunction Photocatalyst and the Application for the Photocatalytic Degradation of Chlorpyrifos under Visible Light Irradiation

“…Previous research has demonstrated the excellent photocatalytic performance of AB 2 O 6 and A 2 B 2 O 7 compounds under visible light exposure [38][39][40]. For instance, Devi et al demonstrated that under visible light exposure for 180 min, the YGdTi 2 O 7 nanophase material achieved a photocatalytic removal efficiency (RME) of 66% for methylene blue [41]. Similarly, Zhang et al studied that the La 2 Ce 2 O 7 photocatalyst powder achieved an RME of 76.6% for methyl orange under visible light exposure for 300 min [42].…”

Photodegradation of Carbol Fuchsin Dye Using an Fe2−xCuxZr2−xWxO7 Photocatalyst under Visible-Light Irradiation

“…Many studies are concerned with metal oxide photocatalysts (with the chemical formula A 2 B 2 O 7 crystallized in a pyrochlore structure) for dye photodegradation. Some examples include Ln 2 Ce 2 O 7 (Ln = Nd, Pr, or Eu) for the degradation of methylene blue (MB) dye [29], YLnTi 2 O 7 (Ln = Nd, Sm, Eu, or Gd) for the degradation of MB [30], K 2 Ta 2 O 6 for the degradation of rhodamine B [31], and Y 2 Ti 2 O 7−x N x for the degradation of MB, rhodamine B, and 4-chlorophenol [32]. Less attention is given to metal oxides with the chemical formula A 2 B 2 O 7 in the defect fluorite phase.…”