The structure of the glass phase in Rb_1-x(NH₄)_xH₂PO₄

X-ray measurements on the glass state of Rb1-x(NH4)xH2PO4 have been made for x = 0.78.0.75.0.72, 0.68 and 0.49. The results show short-range antiferroelectric ordering for r > 0.70 which disappears on warming above 60 K. There is also evidence for a tendency to order with a wave-vector, q = (ζ, O, O), with ζ - 0.350*. The tendency increases with decreasing x and largely disappears on warming above 160 K. © 1985 The Institute of Physics.