			Home About us Contact

Pure Crystals (pure + crystal)

Distribution by Scientific Domains

Physics and Astronomy	50%
Chemistry	50%

Selected Abstracts

Temperature and frequency investigations of the electrical parameters in the TGS ferroelectric transition

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2010
Ciceron Berbecaru
Abstract Pure and D: alanina doped triglycin sulphate (TGS) crystals were grown from aqueous solutions. Fresh cleaved, polished and silver paste painted samples were temperature and frequency investigated. Pure crystals show nonreproducible values of the permittivity and dielectric loss crossing up and down the Curie point. More stable and much lower values of the permittivity and dielectric loss could be noticed for D: alanina doped crystals. Permittivity and loss values show different frequencies behavior related to polar or nonpolar state of crystals. Frequency dependence of permittivity and loss behavior could be related to the general picture of relaxation of different polarization mechanisms and their contributions to permittivity and loss values for dielectric materials. Much smaller and stable values of permittivity and loss, vs. temperature and frequency, were found for doped crystals. Experimental results point out for a more stable structure with dipoles mobility decreased of doped vs. pure TGS crystals. Thus, higher figure of merit of doped TGS crystals point to a major advantage for technical applications (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Pressure measurements of TO-phonon anharmonicity in isotopic ZnS

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004
R. E. Tallman
Abstract We have measured the dependence on pressure of the line-widths of the TO and LO Raman phonons of ,-ZnS. In order to enhance the phenomena observed, and to eliminate possible effects of isotopic disorder, we have measured a nearly isotopically pure crystal, 68Zn32S. The strongly structured pressure effects observed are interpreted on the basis of anharmonic decay and the corresponding two-phonon density of states. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Diphenyldipyridinezinc(II): partial spontaneous resolution of an organometallic reagent

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009
Anders Lennartson
The title compound, [Zn(C6H5)2(C5H5N)2], (I), forms conformationally chiral molecules residing on a twofold axis. The molecules are stacked along c, and these stacks are associated by edge-to-face ,,, interactions. Crystals of (I) belong to the Sohncke space group P21212 and the crystal lattice of (I) is chiral. The crystal batch that was examined consisted of a mixture of enantiomerically pure crystals and crystals twinned by inversion. [source]

Breaking Symmetry: Spontaneous Resolution of a Polyoxometalate

CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2007
Yu Hou
Abstract A chiral polyoxometalate [Hf(PW11O39)2]10, (1) has been prepared and structurally characterized. It crystallizes in the chiral space group P21212, as a conglomerate of two enantiomerically pure crystals in the absence of any chiral source. The absolute configuration of 1 was determined from the Flack parameter by X-ray crystallography. The structure of 1 comprises two lacunary [PW11O39]7, units, each functioning as a tetra-dentate ligand sandwiching an 8-coordinate HfIV centre in a distorted square antiprismatic geometry. Optically active crystals of both enantiomers were spectroscopically distinguishable by means of solid state circular dichroism spectroscopy. This hafnium-substituted polyoxometalate (POM), 1, shows that spontaneous chiral resolution, a rare phenomenon, can be operable in POM systems. [source]