Kristalldaten von α-Ba(OH)2

Abstract

The dimensions of the orthorhombic unit cell of ~-Ba(OH)E, which contains 20 formula units Ba(OH),, are a= 11.03, b=16.56, c=7.11 A. The space group is either Pnma or Pn2~a. lm Zusammenhang mit der Strukturbestimmung von Strontiumhydroxid Sr(OH)z, fiber die in Ki.irze an anderer Stelle berichtet werden soil, haben wir auch r6ntgenogra-phische Studien an Bariumhydroxid begonnen. Dabei fanden wir die Angaben von Michaud (1966)

BaTiO3 Thin Films from Atomic Layer Deposition: A Superlattice Approach

“…The GI-XRD pattern of the as-grown film (200 °C) (Figure b) reveals two very broad peaks indicating low crystallinity in the superlattice after the ALD process. The peak positions can be indexed to the most intense peaks of TiO 2 in the anatase phase and α-Ba­(OH) 2 . The observation of weakly crystalline α-Ba­(OH) 2 at a deposition temperature of 290 °C is consistent with a previous study using very similar precursors for the Ba–O subcycle .…”

“…The peak positions can be indexed to the most intense peaks of TiO 2 in the anatase phase and α-Ba(OH) 2 . 33 The observation of weakly crystalline α-Ba(OH) 2 at a deposition temperature of 290 °C is consistent with a previous study using very similar precursors for the Ba− O subcycle. 12 Up to 500 °C no changes are observed.…”

“…These observations suggest cation interdiffusion between the two layers and the transformation into a more dense structure. Indeed, from the difference in average density between the initial constituents TiO 2 (ρ = 3.88 Mg m –3 ) and BaO (ρ = 5.99 Mg m –3 ) or α-Ba­(OH) 2 (ρ = 4.4 Mg m –3 ) to BaTiO 3 (ρ = 6.05 Mg m –3 ) even higher thickness changes between 18 and 32% would be expected. The considerably lower change points toward porosity within the bulk of the film, which is confirmed by TEM images in Figure e and Figure S7a.…”

“…(b) GI-XRD scans of the same film as a function temperature. The Bragg indices correspond to TiO 2 (blue, anatase-phase), α-Ba­(OH) 2 (pink), and cubic BTO (black).…”

The standard state thermodynamic properties for completely ionized hydrochloric acid and ionization of water up to 523 K

“…Although two phases of solid Ba(OH) 2 have been described in the literature [32,33], a low temperature a phase and a high temperature a phase, at the time the experiments were begun the nature of the transition had not been established. The temperature of 433.55 K is below the transition temperature 521 K [19,34], which indicated that perhaps the sample was a mixture of solids.…”