Vibrational spectroscopic characterization of the phosphate mineral kulanite Ba(Fe(2+),Mn(2+),Mg)2(Al,Fe(3+))2(PO4)3(OH)3.
The mineral kulanite BaFe2Al2(PO4)3(OH)3, a barium iron aluminum phosphate, has been studied by using a combination of electron microscopy and vibrational spectroscopy. Scanning electron microscopy with EDX shows the mineral is homogenous with no other phases present. The Raman spectrum is dominated by an intense band at 1022cm(-1) assigned to the PO4(3-)ν1 symmetric stretching mode. Low intensity Raman bands at 1076, 1110, 1146, 1182cm(-1) are attributed to the PO4(3-)ν3 antisymmetric stretching vibrations. The infrared spectrum shows a complex spectral profile with overlapping bands. Multiple phosphate bending vibrations supports the concept of a reduction in symmetry of the phosphate anion. Raman spectrum at 3211, 3513 and 3533cm(-1) are assigned to the stretching vibrations of the OH units. Vibrational spectroscopy enables aspects on the molecular structure of kulanite to be assessed.
Raman spectroscopy of phosphates of the variscite mineral group
Raman spectra of phosphates of the variscite mineral group, namely strengite, variscite, metavariscite and phosphosiderite, were obtained at 298 and 77 K using a thermal stage and complemented with selected infrared data using a diamond attenuated total reflection cell. Multiple phosphate stretching bands are observed. Bands for strengite at 1006, 1012 and 1026 cm-1 at 298 K and at 997, 1006, 1014 and 1027 cm-1 at 77 K are observed. Variscite is characterized by PO stretching vibrations at 1023, 1005 and 938 cm-1 and phosphosiderite by bands at 1009 and 993 cm-1. These minerals are readily identified by their Raman spectrum both in the PO stretching region and in the low-wavenumber region. Multiple bands attributed to the bending modes of PO4 are identified for each of the minerals. A model is proposed involving non-hydrogen-bonded PO4 and strongly hydrogen-bonded PO4 units together with [Al or Fe(OH)2]+ ·(H2PO4)2--type species. Raman spectroscopy shows that at the molecular level multiple species of phosphate anions exist for the variscite phosphate minerals.
Thermal Conductivity of Toluene+Cyclopentane Mixtures: Measurements and Prediction
New measurements of the thermal conductivity of toluene, cyclopentane, and a binary mixture of 60 wt% toluene are presented. The measurements cover the temperature range from 235 to 345 K and from the saturation line up to 20 MPa pressure. The measurements were performed with a transient hot-wire instrument. The uncertainty of the measurements is estimated to be ±0.5%. The present results are employed to examine the predictive power of a theoretically based scheme for the calculation of the transport properties of mixtures.