English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Open

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

The formation of NaRMn 2 Ti 4 O 12 compounds (R = rare earth) under high pressure (about 6 GPa) and high temperature (about 1750 K) conditions was studied. Such compounds with R = Sm, Eu, Gd, Dy, Ho, Y adopt an A-site columnar-ordered quadruple-perovskite structure with the generic chemical formula A 2 A'A″B 4 O 12 . Their crystal structures were studied by powder synchrotron X-ray and neutron diffraction between 1.5 and 300 K. They maintain a paraelectric structure with centrosymmetric space group P 4 2 / nmc (No. 137) at all temperatures, in comparison with the related CaMnTi 2 O 6 perovskite, in which a ferroelectric transition occurs at 630 K. The centrosymmetric structure was also confirmed by second-harmonic generation. It has a cation distribution of [Na + R 3+ ] A [Mn 2+ ] A' [Mn 2+ ] A″ [Ti 4+  4 ] B O 12 (to match with the generic chemical formula) with statistical distributions of Na + and R 3+ at the large A site and a strongly split position of Mn 2+ at the square-planar A' site. We found a C-type long-range antiferromagnetic structure of Mn 2+ ions at the A' and A″ sites below T  N = 12 K for R = Dy and found that the presence of Dy 3+ disturbs the long-range ordering of Mn 2+ below a second transition at lower temperatures. The first magnetic transition occurs below 8-13 K in all compounds, but the second magnetic transition occurs only for R = Dy, Sm, Eu. All compounds show large dielectric constants of a possible extrinsic origin similar to that of CaCu 3 Ti 4 O 12 . NaRMn 2 Ti 4 O 12 with R = Er-Lu crystallized in the GdFeO 3 -type Pnma perovskite structure, and NaRMn 2 Ti 4 O 12 with R = La, Nd contained two perovskite phases: an AA' 3 B 4 O 12 -type Im 3̅ phase and a GdFeO 3 -type Pnma phase.

inorganic chemistry

High-Pressure Synthesis, Crystal Structures, and Properties of A-Site Columnar-Ordered Quadruple Perovskites NaRMn2Ti4O12 with R = Sm, Eu, Gd, Dy, Ho, Y