Synthesis, growth and optical spectroscopy studies of BaBiBO4 and CaBi2B2O7 crystals

Single-crystalline species of the novel compounds BaBiBO₄ and CaBi₂B₂O₇ with Pna2₁ structure were successfully grown by the top-seed solution growth (TSSG) method and solid-state recrystallization, respectively. X-ray diffraction methods were used to confirm the symmetry of the crystal structure and to determine unit cell parameters. Normal-mode classification and assignment were performed from the results of polarized Raman and IR absorption measurements on the obtained crystals. The high-frequency part of the vibrational spectra of both materials (580–1400 cm^?1) is reminiscent of the normal modes of the isolated [BO₃]^3? group. The expected crystal-field induced changes in these modes from group-theoretical considerations provide important clues for the normal-mode assignment of the high-frequency spectral lines.     

Thermal and thermodynamic data concerning the selenites from group IB in the periodic table

The thermal dehydration of CuSeO₃·2 H₂O, and the thermal dissociation of CuSeO₃ and Ag₂SeO₃ are studied. The mechanism of these processes is suggested. The heats of phase transitions and the specific heats of the corresponding compounds are determined.     

Untersuchung der Phasengleichgewichte in den Systemen Sb2O3?SO3?H2O und Bi2O3?SO3?H2O

Investigation of Phase Equilibria in the Systems Sb₂O₃? SO₃? H₂O and Bi₂O₃? SO₃? H₂O Phase equilibria in the systems Sb₂O₃? SO₃? H₂O and Bi₂O₃? SO₃? H₂O within the concentration range of 1 up to 98.5% H₂SO₄ at 100°C are studied. In the system Sb₂O₃? SO₃? H₂O crystallization fields of five compounds depending on the H₂SO₄ concentration were determined: 5Sb₂O₃ · Sb₂(SO₄)₃ · 3H₂O; 7Sb₂O₃ · 2Sb₂(SO₄)₃; 2Sb₂O₃ · Sb₂(SO₄)₃; Sb₂O₃ · Sb₂(SO₄)₃ and Sb₂(SO₄)₃. The obtained compounds are identified by chemical and derivatographic analysis.     

Löslichkeitsisothermen und thermisches Verhalten der Phasen im System CdSeO4?H2SeO4?H2O bei 100°C

Isotherms of Solubility and Thermal Stability of the Phases in the System CdSeO₄? H₂SeO₄? H₂O at 100°C The isotherms of solubility in the system CdSeO₄? H₂SeO₄? H₂O were studied and constructed at 100°C. Existence fields of CdSeO₄ · H₂O and CdSeO₄ were determined. The compounds are isolated in pure form and their crystallographic characteristics are calculated. The mechanism of thermal dehydration and dissociation is shown.     

Thermodynamic properties of germanium and lead tellurites

The temperature dependence of the molar heat capacities of the tellurites PbTeO₃, Pb₂Te₃O₈ and Ge(TeO₃)₂ are determined. By statistical manipulation of the values obtained, the parameters in the equations for the corresponding compounds showing this dependence are determined using the least-squares method. These equations and the standard molar entropies are used to determine the thermodynamic functions Δ₀ ^T S _m ⁰ , Δ_T ^T H _m ⁰ and (Φ_m ⁰+Δ₀ ^T H _m ⁰/T) for T'=298.15 K.     

Magnetization reversal by electric-field decoupling of magnetic and ferroelectric domain walls in multiferroic-based heterostructures

We demonstrate that the magnetization of a ferromagnet in contact with an antiferromagnetic multiferroic (LuMnO(3)) can be speedily reversed by electric-field pulsing, and the sign of the magnetic exchange bias can switch and recover isothermally. As LuMnO(3) is not ferroelastic, our data conclusively show that this switching is not mediated by strain effects but is a unique electric-field driven decoupling of the ferroelectric and antiferromagnetic domain walls. Their distinct dynamics are essential for the observed magnetic switching.     

Specific heat capacity and thermodynamic properties of CuTeO3 and HgTeO3

Tellurites of CuTeO₃ and HgTeO₃ are synthesized and their specific molar heat capacities are experimentally determined for the first time. The tellurites discussed in the present paper are used for preparation of optical glasses with special properties for optoelectronics, nuclear and power industries. The tellurites synthesized are prepared for chemical analysis, differential thermal analysis and X-ray analysis. The use of the tellurites studied is related to knowing their thermodynamic properties like specific molar heat capacity (C _p,m), enthalpy \( \left( {\Delta_{{{\text {T}}^{\prime}}}^{\text{T}} H_{\text{m}}^{0} } \right), \) entropy \( \left( {\Delta_{{{\text {T}}^{\prime}}}^{\text{T}} S_{\text{m}}^{0} } \right) \) and Gibbs energy \( \left( { - \Delta_{{{\text {T}}^{\prime}}}^{\text{T}} G_{\text{m}}^{0} } \right) \) . The temperature dependences of their molar heat capacities are determined using the least squares method. The thermodynamic properties are calculated: entropy, enthalpy and Gibbs function.