Twinning in La_0.95Sr_0.05Ga_0.9Mg_0.1O_2.92crystal studied by white-beam (Laue) X-ray microdiffraction

Abstract

The investigation of twin structure in La 0.95 Sr 0.05 Ga 0.9 Mg 0.1 O 2.92 perovskite-type crystals has been undertaken using the technique of white-beam X-ray microdiffraction. The sample shows de®nite twinning which is re¯ected in the Laue patterns as apparent splitting of the peaks. Re¯ections from the different domains were indexed separately. Positional shifts of twin domain spots with respect to the reference matrix spot, arising from the mutual misorientation of diffraction vectors, were measured on Laue patterns and compared with calculated values in order to solve the twin laws in this system. The dominant twin operations were found to be (12 " 1) and (10 " 1) mirror re¯ections.

Correlation between high ionic conductivity and twin structure of La0.95Sr0.05Ga0.9Mg0.1O3−δ

“…This may be because a strong boundary effect interferes with the direct observation of the actual features of ionic conduction in the grains. 10,19,20 Studies on the crystal structures of La 0.95 Sr 0.05 Ga 0.9 Mg 0.1 O 3−␦ ͑LSGM͒ solid solution produced by the Czochralski method, 21,22 using high-resolution diffraction synchrotron techniques, provide very important information to the main objective of the present study. LSGM solid solutions exhibit twinning that occurs in a Laue pattern as peak splitting.…”

“…28,29 LSGM undergoes three phase transitions: ͑i͒ orthorhombic to monoclinic ͑Imma-I2/a͒ around 550 K, ͑ii͒ monoclinic to trigonal ͑I2/a-R3c͒ around 690 K, and ͑iii͒ trigonal to trigonal ͑R3c-R3c͒ around 870 K. 21,22 The twin boundary relates a domain to another by a symmetry operation at these phase transitions. 21,22 Since a small amount of experimental knowledge on the ionic transport properties in the twin structures is available, it would be interesting to elucidate the electric conduction in these lattice structures. Furthermore, experimental results of the conduction in the twin structures might facilitate the examination of the correlation between the electric conduction in the twin structures and the ionic conduction in the doped lanthanum gallates.…”

“…[21][22][23][24][25] The widths of the domain walls in LSGM are in the range of 4 -20 nm, 26,27 and the local atomic structure of the domain walls differs from that of the domains. 28,29 LSGM undergoes three phase transitions: ͑i͒ orthorhombic to monoclinic ͑Imma-I2/a͒ around 550 K, ͑ii͒ monoclinic to trigonal ͑I2/a-R3c͒ around 690 K, and ͑iii͒ trigonal to trigonal ͑R3c-R3c͒ around 870 K. 21,22 The twin boundary relates a domain to another by a symmetry operation at these phase transitions. 21,22 Since a small amount of experimental knowledge on the ionic transport properties in the twin structures is available, it would be interesting to elucidate the electric conduction in these lattice structures.…”

Growth and characterization of perovskite LaGaO3 crystals doped with Sr and Mn

“…However, their use is limited because of a strong tendency for twin formation [1,2]. The cause of twinning is the first order phase transition from orthorhombic to rhombohedral (O/R) structure, which occurs on heating near 423 K (150 • C) for LaGaO 3 .…”

Identification of the Domain Walls Configuration in the Ferroelastic Nanosize Material La0.95Sr0.05Ga0.9Mg0.1O3-x

“…For example, the divergence of the majority white beams at different synchrotron sources is smaller than a few milliradians and the space discriminatory limit (20-60 µm per pixel) of modern CCD-detectors allows us to fix the orientation contrast of the domain structure at a value of a few angle minutes. On the other side, the high intensity of synchrotron stations (more than 5 times higher than standard X-ray tubes) and the high sensitivity of CCD--detectors (40 electrons per a photon with λ = 1.54056 Å) allows us to reduce the Laue pattern exposition time to 0.1 s. This tool can therefore be used for the characterization (determination of twin laws, misorientation of domains and domain wall orientations) of the twin structure, both in small crystals of submillimeter sizes [18,19] and very small areas (few µm) of larger samples (white beam X-ray microdiffraction) [20][21][22]. It can be used for in situ measurements under a variety of different experimental conditions, for studies of the reorientation of twin walls at phase transitions in particular.…”