Article

Growth and dc conductivity studies of tripotassium sodium dichromate single crystal

Indian Journal of Physics 01/2010; 84:1123-1128. DOI: 10.1007/s12648-010-0111-2

ABSTRACT DC electrical conductivity studies were carried out along the three crystallographic axes for tripotassium sodium dichromate (K3Na(CrO4) 2 or KNCr). Earlier studies of phase transition in this crystal show successive phase transitions at 239 K and 853 K. In this paper we report the dc electrical conductivity measurements in the temperature region 303–430 K along the crystallographic axes. An anomaly in conductivity was obtained around 326 K along both the axes. This may be attributed as due to a newly observed phase transition in the crystal. DSC taken for the sample also shows exothermic peak supporting the occurrence of newly observed phase transition.

0 Bookmarks
 · 
71 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ultrasonic studies of the temperature behavior of the velocity and damping of sound for the xx and zz longitudinal and yx and zx transverse waves in K3Na(CrO4)2 have been carried out in the temperature interval 185–295 K, which includes the region of the ferroelastic phase transition. The acoustic parameters for both shear and longitudinal waves were found to have anomalies in the region of the phase transition with a Curie temperature of 235.5 K. A theoretical analysis of the softening of the elastic moduli c 44 and c 66 was performed on the basis of the Landau expansion in terms of the strain tensor components ɛ4 and (ɛ2-ɛ1)/2 considered as the linearly coupled primary and secondary order parameter, respectively. The absolute values of the elastic moduli c 11, c 33, c 44, c 66, c 12, and c 14 at 295 K were calculated.
    Physics of the Solid State 03/2004; 46(4):775-779. · 0.77 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The phase transition in K3Na(CrO4)2 single crystals has been studied by electron paramagnetic resonance (EPR) of Mn2+ ions. The values of the spin-Hamiltonian parameters have been evaluated. Below the phase transition temperature, the magnetic z-axis is deflected in ac and bc crystallographic planes by the same angle. Anomalous line shapes recorded below the phase transition temperature suggest the existence of an incommensurate phase.
    Journal of Physics Condensed Matter 12/2003; 15(50):8725. · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Thermal, dielectric, and elastic properties of K3Na(SeO4)2 crystals grown from aqueous solution are studied versus temperature. Two improper structural phase transitions are observed, on cooling, in the temperature range from 300 to 400 K: the nonferroic continuous phase transition with no change of 3m point group at 346 K, and the ferroelastic discontinuous phase transition from the trigonal point group 3m to the monoclinic 2/m one at 334 K. The first transition is manifested as anomalous temperature behaviour of heat capacity and thermal expansion of the crystal. The second one is detected by direct observations of domain structure in the polarized light below 334 K and by softening of elastic moduli in selected crystallographic directions.Die thermischen, dielektrischen und elastischen Eigenschaften von K3Na(SeO4)2-Kristallen, die aus wäßriger Lösung gezüchtet wurden, werden als Funktion der Temperatur untersucht. Im Temperaturbereich von 300 bis 400 K werden beim Abühlen der Kristalle zwei uneigentliche Phasenumwandlungen festgestellt: eine kontinuierliche, nichtferroische Umwandlung in der Punktsymmetriegruppe 3m bei T0 = 346 K und eine nichtkontinuierliche, ferroelastische Umwandlung aus der trigonalen Punktgruppe 3m in die monoklinische 2/m bei Tc = 334 K. Die erste wird als eine anomale Temperaturabhängigkeit der Wärmekapazität und der thermischen Ausdehnungskoeffizienten beobachtet. Die zweite wird direkt durch Beobachtung der Domänenstruktur in polarisiertem Licht bei T < 334 K und als eine Ánderung der elastischen Koeffizienten in ausgewählten kristallographischen Richtungen festgestellt.
    physica status solidi (a) 02/2006; 135(2):557 - 564. · 1.21 Impact Factor