Synthesis of novel compounds with cation ordered fluorite and α-PbO2 related structures by oxidation of Sn2Nb2O7 pyrochlore

Characterization of novel cation-ordered compounds with fluorite and α-PbO2 related structures prepared by oxidation of Sn–Nb–O pyrochlore

“…2(b) and (c) shows XRD patterns of the oxidized samples of the precursor in 1% O 2 /Ar at 673 K and in O 2 at 723 K, respectively. As reported in our previous paper [9], for the oxidation at 673 K in 1% O 2 /Ar, the sample showed a cubic cation-ordered fluorite related structure with aZ1.0173 nm ( Fig. 2(b)), i.e.…”

“…When the precursor was oxidized at 723 K in O 2 , all diffractions were indexed as those for the orthorhombic cell with lattice parameters of aZ0.939 nm, bZ 1.158 nm and cZ1.032 nm. Therefore, the sample oxidized at 723 K was identified as the cation-ordered a-PbO 2 phase as reported previously [9]. Taking into consideration of the transformation mechanism among the precursor pyrochlore, cation-ordered fluorite related, cation-ordered a-PbO 2 and rutile phases, it is probable that the cation-ordered a-PbO 2 phase contained impurity cation-ordered fluorite related phase.…”

“…It was concluded that the ordering style in the oxidized SnNbO 4Cx with a cation-ordered a-PbO 2 phase was not wolframite-type ordering, which is a well-known cationordered a-PbO 2 structure as observed in NiWO 4 [12] and InTaO 4 [13], but pyrochlore-type ordering as shown in Fig. 1(c) based on the formation mechanism [9].…”

“…Recently, we performed low temperature (!1073 K) oxidation of Sn-Nb-O pyrochlore (nominal composition of Sn II 2 Nb 2 O 7 ) as a precursor [9]. Two novel metastable phases with a nominal composition of SnNbO 4Cx were successfully synthesized.…”

Photocatalytic behavior of cerium titanates, CeTiO4 and CeTi2O6 and their composite powders with SrTiO3

“…This may result from the fact that the CeTiO 4 phase is formed by oxygen insertion in the Ce 2 Ti 2 O 7 phase, retaining the arrangement of Ce and Ti ions. The present result is in line with the appearance of κ-type CeZrO 4 [14][15][16] and κ-related SnNbO 4 [21] which were obtained by the oxidation of pyrochlore-type Ce 2 Zr 2 O 7 and Sn 2 Nb 2 O 7 . The crystal structure of the CeTiO 4 powder synthesized in this study was completely different from that of the pur- chased CeTiO 4 (PB).…”