Metal-insulator transition in Ba3-xSrxNb5O15

We investigated single crystals of Ba3-xSrxNb5O15 with a tetragonal tungsten bronze (TTB) structure, which exhibits a metal-insulator transition with x. We found that there is a one-dimensional anisotropy with a higher dc conductivity along the c axis in the metallic phase, but it disappears in the insulating phase. The optical conductivity spectra of the metallic samples show similar anisotropy to the dc conductivity, but the anisotropy persists even in the insulating phase. These experimental results, together with the result of magnetic susceptibility, indicate that the disorder caused by the Sr ions loosely bound to the surrounding oxygen ions plays an important role in the metal-insulator transition.

Automated summary

This study revealed the one-dimensional anisotropy of Ba3-xSrxNb5O15 single crystals during the metal-insulator transition, which is primarily influenced by the disorder caused by loosely bound Sr ions to the surrounding oxygen ions.