Structural behavior of Pd40Cu30Ni10P20 bulk metallic glass below and above the glass transition

The thermal behavior of the structure of Pd40Cu30Ni10P20 bulk metallic glass has been investigated in situ through the glass transition by means of high-temperature x-ray synchrotron diffraction. The dependence of the x-ray structure factor S(q) of the Pd40Cu30Ni10P20 glass on temperature follows the Debye theory up to the glass transition with a Debye temperature θ=296 K. Above the glass transition temperature Tg, the temperature dependence of S(q) is altered, pointing to a continuous development of structural changes in the liquid with temperature. The atomic pair correlation functions g(r) indicate changes in short-range-order parameters of the first and the second neighborhood with temperature. The temperature dependence of structural parameters is different in glass and in supercooled liquid, with a continuous behavior through the glass transition. The nearest-neighbor distance decreases with temperature, changing the slope at Tg. The interatomic distances of higher coordination shells expand analogously to the macroscopic linear thermal expansion.