A.V. Beluskin (Frank Laboratory of Neutron Physics, JINR, 141980 Dubna, Russia) and L.A. Shuvalov (Institute of Crystallography, 117333 Moscow, Russia)
The results of neutron diffraction, inelastic and quasielastic neutron
scattering studies on mixed crystals
K1-x(NH4)xH2PO4 will
be presented.
The anomalous behaviour of the proton glass system which is formed for
ammonium concentration 0.2<x<0.8 is compared with the relevant properties
parent ferroelectric KH2PO4 and antiferroelectric
NH4H2PO4 crystals. The following effects
to be discussed:
a) influence of the proton glass transition on crystal structure;
b) the effect of random bonds and random fields on proton dynamics;
c) anomalous increase of mean square displacements of protons in hydrogen
in the glass phase;
d) gradual freezing of the rotational dynamics of ammonium ions in the
paraelectric phase of the glass composition samples and an order parameter
of NH4 groups.
The results of present studies will be compared with the data obtained by
experimental techniques: dielectric susceptibility, NMR, EPR, X-ray
diffraction, optical spectroscopy.