A survey of structural types of borates and polyborates

Es wurde erstmals Na4B2O5 in Einkristallen dargestellt, monoklin, Raumgruppe C2/cC, mit a = 10,618 (2), b = 8,015 (1), c = 6,287 (2) A, β = 110,10 (1)°; Z = 4, d0 = 2,46, dc = 2,557 gcm−3. Die Struktur wurde mit Direkten Methoden gelost (R = 4,6% fur 1010 symmetrieunabhangige Reflexe). Charakteristisch sind [B2O5]-Gruppen mit Punktsymmetrie 2; sie werden mit anderen dieser Art verglichen. Der Madelunganteil der Gitterenergie, MAPLE, und Effektive Koordinationszahlen, ECoN, werden berechnet und diskutiert.



About Borates of Alkali Metals. III. On Na4B2O5



Na4B2O5 was obtained as single crystals for the first time; monoclinic, C2/cC with a = 10.618 (2), b = 8.015 (1), c = 6.287 (2) A; β = 110.10 (1)°; Z = 4, d0 = 2.46, dc = 2.557 g/cm−3. The structure was solved by direct methods; R = 4.6% for 1010 independend reflections. The crystal structure contains [B2O5] groups, which exhibit point symmetry 2. A comparison with already known groups of this kind is given.



The Madelung part of lattice energy, MAPLE and Effective Coordination Numbers, ECoN, are calculated and discussed.

Über Borate der Alkalimetalle. III. Zur Kenntnis von Na4B2O5

Phase equilibria in the system CdO-ZnO-B2O3 were investigated at 850 °C using quenching and X-ray powder diffraction techniques. The binary phases reported previously were confirmed. The ternary phase diagram was solved and a new phase postulated: 3CdO · 3ZnO · 2B2O3. X-ray powder data are given for this. Solid solution effects were investigated for the primary and binary phases by comparison of patterns; none were detected. These results are compared with those of a previous determination and the differences discussed.

Phase equilibria in the system CdO-ZnO-B2O3 at 850°C

Phase equilibria in the system CdO-B2O3-SiO2 were investigated at 800° C using X-ray powder diffraction techniques. The binary phases reported previously were confirmed, but no ternary phases were found. Solid solution effects were investigated for the primary and binary phases by comparison of patterns; no solid solutions were detected. The relationship of the phase diagram to the composition of photoconductive oxide glasses is discussed and suggestions are made of possible mechanisms responsible for the photoelectric effects.

Phase equilibria in the system CdO-B2O3-GeO2 at 800°C

Polycrystalline samples of undoped, terbium-doped (CdB4O7:Tb3+), and manganese-doped (CdB4O7:Mn2+) cadmium tetraborate have been prepared by solid-state reactions at 850°C. Using differential scanning calorimetry and X-ray diffraction, we have determined the melting point of CdB4O7 (t
 m = 976°C) and shown that this compound melts incongruently. The observed monotonic decrease in the orthorhombic cell parameters of the doped materials indicates the formation of substitutional solid solutions (sp. gr. Pbca). The thermoluminescence intensity of the doped materials has been shown to depend on the nature and concentration of the activators and the irradiation time.

J. Krogh-Moe

Papers

New Data on the System CdO—B2O3