Twinning of LaGaO₃single crystals

Abstract

LaGaO3 single crystals, grown by the method of zone melting without a crucible, with radiation heating, were investigated by X-ray topography and diffractometry. It has been found that at 293 K these crystals have an orthorhombic unit cell with a = 5.520(2), b = 5.490(2), c=7.770 (I)A and twinning in the { 110}/(IT0) and { 112}/(1]-0) systems simultaneously. Regions of cross-twinning have been discovered in these systems. A first-order phase transition from orthorhombic to rhombohedral has been observed at 412.5K, the cell parameters being a=3.889A, = 89.50 ° (423 K). The rhombohedral phase has a developed twin structure in the {100}/(001) and {110}/(001) systems. During transformation the structure undergoes an inherited change to the twin structure of the orthorhombic phase.

Analyzing indentation behavior of LaGaO3 single crystals using sharp indenters

“…12 Some authors 13 have suggested a considerable higher temperature (875 • C) for the phase transition, but recent studies 1,14 are in agreement with the lower transition temperature. A second-order phase transition from rhombohedral to monoclinic structure has also been suggested 15 in the temperature range ∼750 to ∼1000 • C. The melting point of LaGaO 3 is 1800 • C. 12 The appearance of twins is common in the perovskite and related structures. It should be noted that although the coefficient of thermal expansion (CTE) for LaGaO 3 above the transition temperature provides an ideal lattice match for high temperature superconducting films, the presence of the disruptive low-temperature phase transition and a strong tendency for twinning restrict its wider application as a substrate material.…”

X- ray and AFM studies of Bi2Sr2CaCu2O8+x single-crystals grown by different methods

“…The domain structure of the single crystals has been investigated by the methods of X-ray angular y-2y and y-scanning topography [16]. In these methods the sample is rotated at an angular rate o.…”

Symmetry Pattern and Domain Wall Structure in GdFeO3Perovskite Type

“…X-ray topography [29,32,34] allowed to find the orientation of domain states or the composition planes between domains. Various models of domain pairs have been developed to explain the experimental results.…”

“…Ferroic domain structures have been investigated in a large number of chemical compositions with the structure of the GdFeO 3 type: natural and synthetic CaTiO 3 crystals [12,[25][26][27][28], (Mg,Fe)SiO 3 [14,26], CaGeO 3 , MnGeO 3 , SmAlO 3 [14], LaGaO 3 [29][30][31][32][33][34], NdGaO 3 [8,35].…”