Mixed phosphates K2MIIIMV(OPO4)2: Heterovalence-substituted analogs of KTiOPO4

A series of heterovalence-substituted analogs of KTiOPO₄ of the general composition K₂M^IIIM^V(OPO₄)₂ (M^III = Cr, Fe, In; M^V = Nb, Ta) were synthesized by crystallization from melts and by solid-phase reactions. Influence of the nature of tri-and pentavalent metals on the conditions of preparation and on the features of phase formation of substituted mixed phosphates was examined. The compounds obtained were characterized by X-ray diffraction analysis and by diffuse reflection spectroscopy.     

NO 3 2− and CO 2 − centers in synthetic hydroxyapatite: Features of the formation under γ- and UV-irradiations

The EPR studies of synthetic hydroxyapatite containing carbonate and nitrate ions exposed to γ-ray and UV irradiations have been performed. It has been found that γ irradiation leads to the formation of both NO₃²⁻ and CO₂⁻ paramagnetic centers, while the UV irradiation induces only NO₃²⁻ centers. To explain this fact, the hypothesis has been proposed, according to which in the hydroxyapatites studied, there coexist complexes consisting of nitrate ions and shallow electron traps that serve as sources of secondary electrons during UV irradiation. The EPR spectroscopy parameters (g and A) of the detected centers have been determined and compared with similar centers in hydroxyapatite with a different impurity composition. The study of the thermal stability of the centers has demonstrated that, in the temperature range 20–300°C, the NO₃²⁻ centers formed by UV irradiation are more stable than the same centers created by γ-ray irradiation.     

Radiation-induced defects in annealed carbonate-containing hydroxyapatite

The effect of preliminary (before irradiation) annealing of synthetic carbonate-containing hydroxyapatite powders on the formation of paramagnetic centers under γ-ray and ultraviolet irradiation has been investigated. Annealing of the samples has been performed in the temperature range from 100 to 700°C. It has been found that electron paramagnetic resonance spectra of radiation-induced defects depend substantially on the annealing temperature. The paramagnetic centers CO ₂ ^? dominate in the samples annealed to 250°C (γ-ray irradiation) and 500°C (ultraviolet irradiation). In the samples annealed above 400°C, other defects, in particular, the O^? and CO ₃ ^3? centers, play a significant role. Annealing at some temperatures leads to an increase in the radiation sensitivity of the material. The observed effects can be associated with the escape of molecular water from the annealed hydroxyapatite samples and with the corresponding transformation of the defect subsystem of the material.     

Synthesis of complex phosphates with a langbeinite structure from melts

Phase formation processes were studied and features of the crystallization of complex phosphates with a langbeinite structure from potassium phosphate melts were established. The compounds obtained were characterized by X-ray phase analysis, IR spectroscopy, diffuse reflection spectroscopy, and ESR spectroscopy.     

Characteristic features of crystallization in alkali metal (Na,K) phosphate vanadate flux systems containing calcium(II) and yttrium(III)

We have studied crystallization behavior in M₂¹O-P₂O₅-V₂O₅-CaO and M₂¹O-P₂O₅-V₂O₅-CaO-YF₃ flux systems (M¹= Na, K) for discrete ratios P/V = 0.04-0.14 and M¹/(P+V) = 0.7, 1.0, 1.2, 1.4, w(CaO) = w(YF3) = 5 wt.%. We established the conditions for the formation of phosphate vanadates based on apatite, whitlockite, NaCaPO₄, KCaY(PO₄)₂, and YPO₄ structural types.     

Magnetic resonance line shape

The long-time asymptote of the magnetization correlation function and its distribution are investigated with slow motion of the spin and molecular subsystem taken into account the most. The influence of molecular drift in the field of the thermal hydrodynamic fluctuations on the magnetic resonance line shape is examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 118–121, May, 1976.     

Determination of indium,chromium, and iron in double alkali phosphate compounds

A procedure is presented for the determination of indium, chromium, and iron in complex phosphate compounds of the type M^IM^IIIP₂O₇, M^I is Li, Na, or K; M^III is Fe, Cr, or In and in solid solutions based on the above phosphates. The procedure is based on X-ray fluorescence spectrometric analysis. It was demonstrated that this method exhibits adequate accuracy of the determination of In, Fe, and Cr and can be recommended for the rapid analysis of samples.     

Theory of rotational Brownian motion

The correlation function for the angular velocity of a Brownian particle suspended in a liquid is analyzed with an account of the viscous aftereffect. The main term in the asymptotic exression for this function is equal to the eddy correlation function for the translational velocity of a liquid found from the Navier-Stokes equations.Translated from Izvestiya VUZ. Fizika, No. 10, pp. 13–17, October, 1969.In conclusion the author thanks Professor I. Z. Fisher for guidance and for constant interest in his study.