Influence of defects on the incommensurate modulation in irradiated Ba sub 2 NaNb sub 5 O sub 15

Journal Article · Wed May 01 04:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.11154· OSTI ID:5685542

Barre, S; Mutka, H; Roucau, C ^[1]; Litzler, A; Schneck, J; Toledano, J C ^[2]; Bouffard, S ^[3]; Rullier-Albenque, F ^[4]

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1. Laboratoire d'Optique Electronique du Centre National de la Recherche Scientifique, Boite Postale 4347, 31055 Toulouse CEDEX, France (FR)
2. Centre National d'Etudes des Telecommunications, 196 avenue Henri Ravera, 92220 Bagneux, France (FR)
3. Centre Interdisciplinaire de Recherche sur les Ions Lourds, Boite Postale 5133, 14040 Caen CEDEX, France (FR)
4. Laboratoire des Solides Irradies, Ecole Polytechnique, 91128 Palaiseau CEDEX, France (FR)

Defect-induced properties of barium sodium niobate (Ba{sub 2}NaNb{sub 5}O{sub 15}) have been studied as a function of electron irradiation dose. Birefringence measurements at low doses indicate that the lock-in transition temperature, originally at about 280 {degree}C, decreases linearly with increasing dose. Complementary irradiations {ital in} {ital situ} in a high-voltage electron microscope show that the incommensurate phase can be stabilized down to room temperature. Simultaneously the satellite diffraction spots broaden and the lock-in transition becomes diffuse. The modification of the hysteresis of the birefringence, observed already at the lowest doses, indicates a progressive extension of the stability range of the 2{ital q} modulated phase to lower temperatures as the defect concentration increases. A similar conclusion can be drawn from the satellite reflection dark-field electron micrographs that show, once the incommensurate phase is stabilized at room temperature, the doubly modulated texture characteristic of the 2{ital q} modulated phase. Low doses of irradiation do not change qualitatively the configuration of the residual discommensurations in the lock-in phase nor the temperature dependence of the incommensurability. Accordingly, already in the as-grown samples the defects dominate the pinning of the incommensurate modulation and the intrinsic properties of this incommensurate system are not clearly observable.

• OSTI ID: 5685542
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 43:13; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360605* -- Materials-- Radiation Effects
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BIREFRINGENCE
COLLISIONS
ELECTRON COLLISIONS
ELECTRON MICROSCOPY
MICROSCOPY
MODULATION
NIOBATES
NIOBIUM COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
REFRACTION
REFRACTORY METAL COMPOUNDS
SODIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS