Structural properties in Sr0.61a0.39Nb2O6 in the temperature range 10 K to 500 K investigated by high-resolution neutron powder diffraction and specific heat measurements

TL;DR

This study uses high-resolution neutron diffraction and specific heat measurements to analyze the structural properties of Sr0.61Ba0.39Nb2O6 across 10-500 K, revealing subtle incommensurate modulations and early onset of ferroelectric transition effects.

Contribution

It provides detailed insights into the temperature-dependent structural behavior of Sr0.61Ba0.39Nb2O6, highlighting the absence of structural phase transitions and early ferroelectric changes.

Findings

Low-temperature anomalies linked to incommensurate modulation changes

No structural phase transition observed in average structure

Structural changes begin around 200K before the ferroelectric transition

Abstract

We report high-resolution neutron powder diffraction on Sr0.61Ba0.39Nb2O6, SBN61, in the temperature range 15-500 K. The results indicate that the low-temperature anomalies (T<100K) observed in the dielectric dispersion are due to small changes in the incommensurate modulation of the NbO6-octahedra, as no structural phase transition of the average structure was observed. This interpretation is supported by specific heat measurements, which show no latent heat, but a glass-like behavior at low temperatures. Furthermore we find that the structural changes connected with the ferroelectric phase transition at Tc approx. 350K start already at 200K, explaining the anisotropic thermal expansion in the temperature range 200-300K observed in a recent x-ray diffraction study.