Characterization of certain phase transitions in the V-D and V-H systems

Phase transitions in the V-D (VDsub(x)) system in the range of compositions 0.63 <= x <= 0.80 and temperatures 100-300 K have been studied using electrical resistivity and differential scanning calorimetry. Comparison has been made with previous work on this and the VHsub(x) system. In particular, the low temperature γ→delta and delta→β transitions near the respective stoichiometric compositions V4D3 and V3H2 were investigated. General considerations indicate that these are likely to be first order with a small or zero mixed phase field. By contrast, the β1-β2 transition in V2H is probably second order with a critical exponent, based on resistivity measurements, of approximately 0.35. The variation with temperature of the long-range order parameter has been deduced for γ phase V4D3 and delta phase V3H2 from the resistivity data. (Auth.)