Tunable Thermal Expansion Behavior in the Intermetallic YbGaGe

TL;DR

This study explores how light doping with carbon and boron affects the thermal expansion of YbGaGe, revealing that doping induces near-zero expansion likely due to substitutional disorder rather than valence fluctuations.

Contribution

It demonstrates that light C and B doping significantly reduces thermal expansion in YbGaGe, challenging previous explanations based on valence fluctuations.

Findings

Pure YbGaGe shows positive thermal expansion (~0.94%) from 10K to 300K.

Doped samples exhibit near-zero volume expansion, indicating strong suppression.

Doping effects suggest substitutional disorder as the mechanism for zero expansion.

Abstract

We investigate the effects of carbon and boron doping on the thermal expansion in the hexagonal (P63/mmc) intermetallic YbGaGe. X-ray powder diffraction was used to measure the lattice constants on pure and doped (C or B at nominal levels of 0.5 %) samples from T~10 K to T~300 K. Also measured were resistivity, specific-heat, and magnetic susceptibility. While the pure YbGaGe samples exhibit positive thermal volume expansion, (V300K-V10K)/V300K = 0.94%, the volume expansion in the lightly C and B-doped samples, contract and tend towards zero volume expansion. Such a strong response with such light doping suggests that the underlying mechanism for the reported zero volume expansion is substitutional disorder, and not the previously proposed valence fluctuations.