Abstract
Structural phase transitions at 87 K and 103 K are reported for single-crystalline Han Blue (BaCuSi4O10) by means of high-resolution thermal-expansion, thermal conductivity and heat capacity measurements. The phase transition at 103 K results in differing lengths of the a and b lattice parameters, and thus a lowering of the crystallographic symmetry. Negative thermal-expansion coefficients are observed perpendicular to the c-axis over a wide temperature range (108K<T<350K). The thermal conductivity is small, and decreases with temperature, both of which suggest strong scattering of heat-carrying phonons. The principle Grüneisen parameter within the plane and perpendicular to it was determined to be γ1=-1.09 and γ3=1.06 at room temperature; the bulk Grüneisen parameter is γ=0.10. The results are consistent with the presence of low-energy vibrations associated with the collective motions of CuO4 and Si4O10 polyhedral subunits.
Original language | English (US) |
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Pages (from-to) | 69-74 |
Number of pages | 6 |
Journal | Journal of Physics and Chemistry of Solids |
Volume | 85 |
DOIs | |
State | Published - May 4 2015 |
Keywords
- Crystal structure
- Optical materials
- Specific heat
- Thermal conductivity
- Thermal expansion
ASJC Scopus subject areas
- Chemistry(all)
- Materials Science(all)
- Condensed Matter Physics