The subsolidus phase relations in the ternary system La2O3–Bi2O3–CuO at 900 °C were investigated by X-ray powder diffraction. A new binary compound, Bi2La4O9, was found, as well as a binary and a ternary solid solution series, Bi1−xLaxO1.5 (0.16≤x≤0.33) and La2−xBixCuO4 (0≤x≤0.11), respectively.

The ternary phase diagram of the system Bi2O3-CdO-GeO2 was investigated in several isothermal sections using predominantly X-ray powder diffraction. The following phases are described with respect to their crystal chemistry, phase relations and powder patterns: Bi2−2xCd2x(O3−x⍽9+x) (solid solution with anti-α-AgI structure), CdGeO3 (complicated polymorphism), Bi12GeO20 (stoichiometric sillenite), Cd-sillenite (solid solution), Bi1.8Cd0.2GeO4.9 (metastable, new phase, new structure type with GeO5 polyhedra), Bi2CdGeO6 (new ternary oxide, new structure type).

The structure of Bi2CdO2[GeO4] was solvedab initioon the basis of laboratory and synchrotron X-ray powder data. The high temperature orthorhombic phase, stable at room temperature, crystallizes inPbcn(60),Z= 8,a= 10.4969(1) Å,b= 10.0944(1) Å,c= 5.60601(3) Å, andV= 594.01(1)Å3with 14 refinable positional parameters. The structure consists of [GeO4] tetrahedra, strongly distorted trigonal [CdO6] prisms and irregular [BiO4+2] polyhedra. At low temperatures, the material undergoes a small distortion to monoclinic symmetry (γ = 90.37° at 20 K).

The binary system Bi2O3–La2O3with La2O3≥ 50 mole% has been investigated at 950–1000°C. The results revealed three compounds: Bi8La10O27, Bi2.4La3.6O9, and Bi2La4O9. Bi2.4La3.6O9has a rhombohedral subcell with hexagonal lattice parametersa= 3.96017(5) Å,c= 9.9691(2) Å, and space groupR3m. It is probably the same phase which was reported previously as Bi2La4O9(Refs. 5 and 6). Bi2La4O9has a monoclinic structure with the subcell lattice parametersa= 6.8290(3) Å,b= 3.9887(1) Å,c= 4.0524(1) Å and β = 125.094(3)° and subcell space groupC2/m. Its average structure has been determined by X-ray powder diffraction and refined by the Rietveld method. The average structure can be described as an oxygen deficient fluorite structure of the δ-Bi2O3type with La and Bi randomly distributed on the cation site. In addition, a superstructure has been observed by TEM.

Crystals of ammonium hydrogen succinate undergo the sec-OQd order phase transition around 170 K, and the space group is P1 with Z=2 at 293 K (Haussi.ihl& Schreuer, 1993).We report the structural change accompaning the phase transition based on the structur~s determined at temperatures from 297 to 20 K.The space group P1 is retained, and hydrogen atoms involved in two 0 -H-••0 hydrogen bonds between hydrogen succinate ions are disordered at all temperatures.Temperature dependency of the structure is remarkable in the 0•••0 lengths of these hydrogen bonds.These lengths decrease with a decrease in temperature from room temperature to the phase-trasition temperature, but increase after the phase transition.It is worthy of note that peak resolution of the difference Fourier maps in regions of these hydrogen bonds becomes lower at 80 and 20 K than at 150 K, suggesting some fluctuations in hydrogen-atom positions.Intensity data were measured on a Hi.iber off-center four-circle diffractometer in 2 q range of 3-78° by using Mo Ka X radiation.Final R values were 0.033 for 2720 reflections at 80 K, and 0.034 for 2819 reflections at 20 K.

The systems PbO–Bi2O3–P2O5/As2O5/V2O5 have been studied with respect to their compounds and solid solutions. A number of new compounds, particularly with high-Bi contents were found. Most of them are structurally closely related to the CaF2 and δ-Bi2O3 structures. Several binary and ternary solid solutions with P/As/V substitutions were investigated.

A procedure is described to determine the limit of detection of DSC instruments by using tiny signals from spontaneous polymorphic transitions of CsCl, K2Cr2O7 and Na2SO4. It is shown how such signals can be found well-resolved in DSC diagrams of powder samples. To distinguish them from the baseline noise they should exhibit a height at least twice that of the baseline width. For the instrument employed the corresponding smallest amount of heat, i.e., the limit of detection, was found to be 0.1 mJ.

A structural family of the summarizing formula M5-pT4+pO14 with p = 0 or p = 1 is described. It comprises three structure types I, II and III and a large number of compounds. The structure types of I (P321) and II (I2/a) are known. For the unknown monoclinic structure of III a partial structure proposal is developed. The basic unit of all structures is a strongly folded tetrahedral vierer single chain with Ge or Ga as predominant tetrahedral ions T. An unusually large variety of cations M is observed with eightfold positions occupied by mono- to trivalent ions (e.g. Na+, Sr2+, Nd3+) and octahedral sites occupied by bi- to pentavalent ions (e.g. Mg2+, Ga3+, Ge4+, Sb5+). 25 new compounds were synthesized, enlarging the total number of known representatives to 80.72 of them belong to structure type I, seven to type II and one to type III. Several solid solution series were investigated.

Using optical measurements on single crystals, the speed of first order transitions (K2Cr207, KNO3, AgNO3) was determined and compared with the strongly smeared DSC signals. Such optical measurements are proposed to select materials which are suitable for the determination of the DSC apparatus function.

Article Structural and chemical varieties of dioptase, Cu6[Si6O18] · 6 H2O I. Thermal properties was published on November 1, 1988 in the journal Zeitschrift für Kristallographie - Crystalline Materials (volume 184, issue 1-4).

A survey of the application of thermal analytical methods in the earth sciences with respect to various materials and temperature ranges is presented. Five papers presented at the ICTA 1985 in Bratislava serve as excellent examples of the diversity of TA investigations in earth sciences. In these papers fields such as organic and inorganic components of soils and coal, properties of uranium minerals and silica transitions are discussed. Typically, the TA studies are combined with other methods such as IR spectroscopy and X-ray diffraction.