Aqueous Chemical Synthesis of Ln2Sn2O7 Pyrochlore‐Structured Ceramics

Pyrochlore‐structured lanthanide stannate ceramic (Ln₂Sn₂O₇) has been synthesized via a new complex precipitation method. A suite of characterization techniques, including FTIR, Raman, X‐ray, and electron diffraction as well as nitrogen sorption were employed to investigate the structural evolution of the synthesized and calcined powder. Raman, XRD, and selected area electron diffraction results confirm the presence of the pyrochlore structure after calcination of the powder above 1200°C. TEM imaging shows fine crystallites gradually increased in size from approximately 100 nm to about 500 nm with higher calcination temperatures. Grain growth and powder densification upon increasing the calcination temperature was confirmed by nitrogen sorption results. This aqueous synthetic method provides a simple pathway for the preparation of homogeneous lanthanide stannate ceramics.     

The transfer effect in artificial grammar learning: Reappraising the evidence on the transfer of sequential dependencies.

Exposure to sequences of elements generated by an artificial grammar enables observers to classify new sequences presented either with the same (within-domain) or different (across-domain) vocabulary elements as being well- or ill-formed according to that grammar (A. S. Reber, 1969). Experiment 1 replicated G. T. M. Altmann, Z. Dienes, and A. Goode's (1995) demonstration of this effect, but inspection of hits and correct rejections revealed that a single cue was used to reject a subset of the ungrammatical sequences. Experiment 2 removed this cue, and participants no longer discriminated between grammatical and ungrammatical sequences in the novel domain. The authors conclude that G. T. M. Altmann et al.'s demonstration of discrimination in the novel domain did not necessitate the application of knowledge pertaining to sequential dependencies. Implications of the data for other studies, showing abstraction of knowledge across test sequences, are also considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)