Experimental Studies on Mixed Ferro-Antiferroelectric Glasses

• Published in: Japanese Journal of Applied Physics 1985, Vol.24 (S2), p.70-74
• Main Author: Courtens, Eric
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAPS.24S2.70

The growth, structure, and dynamics of RbH 2 PO 4 –NH 4 H 2 PO 4 mixed crystals are reviewed. In the intermediate concentration range, the built-in frustration of these materials prevents the ordinary ferroelectric or antiferroelectric transitions, whereby the disordered acid-proton sublattice freezes into a glass. This has been observed with a number of experimental techniques, including dielectric dispersion, optical birefringence, X-ray diffraction and scattering, Raman and Brillouin scattering, NMR, and more recently, specific-heat and neutron scattering. The variety of techniques applicable to this system has allowed the observation of polarization freezing over about 17 orders of magnitude in frequency. This freezing is well described phenomenologically by the Vogel-Fulcher law, while other laws proposed for spinglasses are less successful. Recent hypersonic-relaxation measurements point to the existence of a frozen polarization component at temperatures already much above Vogel-Fulcher freezing, while neutron diffused scattering reveals that the tendency to form superstructures is not static.