title: Dielectric properties of (NH(4))(2)SO(4) crystals in the range of electronic excitations.
abstract: Spectra of the real and imaginary parts of the pseudo-dielectric permittivity, (1)(E) and (2)(E), of ferroelectric ammonium sulfate crystals, (NH(4))(2)SO(4), have been measured in the range of electronic excitations 4.0 to 9.5 eV by ellipsometry using synchrotron radiation. Temperature dependences of the corresponding susceptibilities, chi(1)(T) and chi(2)(T), obtained for the photon energy E = 8.5 eV, related to excitations of oxygen p-electrons, reveal sharp peak-like temperature changes near the Curie point T(C) = 223 K. The large temperature-dependent increase of the imaginary part of the susceptibility chi(2)(T), together with a simultaneous decrease of the real part of the susceptibility chi(1)(T), take place at the phase transition. These anomalies have been ascribed mainly to the SO(4) group of the crystal structure.
authors.affiliation: Faculty of Electronics and Computer Sciences, Koszalin University of Technology, 2 Rniadeckich St, PL-75-453 Koszalin, Poland. bohdan.andriyevskyy@tu.koszalin.pl
authors.forename: B
authors.initials: B
authors.lastname: Andriyevsky
authors.forename: C
authors.initials: C
authors.lastname: Cobet
authors.forename: A
authors.initials: A
authors.lastname: Patryn
authors.forename: N
authors.initials: N
authors.lastname: Esser
mesh_terms: D000645:Ammonium Sulfate / Q000737:chemistry* / Q000528:radiation effects*; D003460:Crystallization / Q000379:methods*; D004553:Electric Conductivity; D011829:Radiation Dosage; D017356:Synchrotrons
chemical_list: D000645:Ammonium Sulfate