Obtaining and properties of CdB4O7 polycrystals, doped with Cr3+ions

Впервые поликристаллические фазы Cd1-xB4O7 : xCr3+ (x = 0,03; 0,05 и 0,07) и исходная матрица CdB4O7 синтезированы высокотемпературными твердофазными реакциями при 850 °С. Методом РФА показано, что твердые растворы кристаллизуются в ромбической сингонии (пр. гр. Pbca). Методом ДСК определена температура плавления (Тпл. = 974 °С) бората Cd1-xB4O7 : 0.03 Cr3+. Построением кривых высвечивания в области 20–400 °С проведены термолюминесцентные исследования. Выявлен оптимальный состав люминофора Cd1-xB4O7 : 0.03 Cr3+ с максимальной интенсивностью свечения. For the first time the polycrystalline phases Cd1-xB4O7 : x Cr3 + (x = 0.03; 0.05 and 0.07) and the initial CdB4O7 matrix were synthesized by high-temperature solid-state reactions at 850°C. The XRD method showed that solid solutions crystallize in rhombic system (sp. gr. Pbca). Using the DSC method, the melting point (Tm.p. = 974°С) of Cd1-xB4O7 : 0.03 Cr3 + borate was determined. Thermoluminescent studies were performed by plotting the emission curves in the range of 20–400°С. The optimal composition of the phosphor Cd1-xB4O7 : 0.03 Cr3 + with a maximum luminescence intensity was revealed.

A study of cordierite ceramics synthesis from serpentine tailing and kaolin tailing

Cordierite ceramics was synthesized using a composition prepared by the mixture of three different materials: waste serpentine mine tailing (WST), waste kaolin mine tailing (WKT) and alumina. The formation of cordierite was achieved with the solid-state sintering reactions at 1350?C for 3 h. The synthesized cordierite ceramics was characterized by X-ray diffractometer (XRD), thermal analysis (TG-DTA), and SEM-EDS (Scanning Electron Microscopy-Energy Dispersive Spectrometer). The XRD analysis results showed the cordierite with typical rhombic system as a major phase, and its compositions consisted of O, Al, Si and Mg by means of SEM-EDS.

Some anomalous optical properties of freshly-prepared mixed crystals of the Seignette salts

The new crystalline compound triphenyl-bismuthine dichloride, described crystallographically by Mr. G. Greenwood (Min. Mag., 1923, vol. 20, p. 123), possesses the remarkable property of exhibiting crossed axial-plane dispersion of the rhombic ‘brookite’ type and circular polarization. For purposes of comparison, the author prepared specimens of the mixed Seiguette salts, which also exhibit crossed axial-plane dispersion together with circular polarization. The Seignette salts, sodium-potassium tartrate and sodium-ammonium tartrato, crystallize each with four molecules of water ill the bisphenoidal class of the rhombic system. They are truly isomorphous and form a continuous series of mixtures. The acute bisectrix for sodium-ammonium tartrate is normal to (001)and for sodium-potassium tartrate normal to (100). For all proportions of mixture containing 5 % and over of sodium-ammonium tartrate, the acute bisectrix is normal to (001).

On Bassetite and Uranospathite, new species hitherto classed as Autunite

The name autunite was originally g!ven to the well-known mineral from Autun, but it would seem that no crystals of this material have been found that would afford measurements oi1 the goniometer. As the result of optical examination Des Cloizeaux (2) concluded that the mineral was biaxial, and he observed further that the angle decreased when the specimen was heated (6); the extinction was apparently straight, and he therefore referred the trysts,Is to the rhombic system ; with the contact goniometer he found mm'=90°48'.