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This paper presents the results of mineralogical and crystal chemical studies of leightonite K2Ca2Cu(SO4)4·2H2O from the Kamchatka Peninsula (Russia), including an investigation of its thermal behavior in a wide temperature range (–180 ≤ T ≤ 325°C). The following methods were used: energy dispersive X-ray spectral analysis, single-crystal and powder X-ray diffraction, and in situ powder X-ray diffraction at negative and high temperatures). The temperature range of the existence of the mineral are established, the main values of the thermal expansion tensor are calculated, and a structural interpretation of thermal expansion is given. The mineral crystallizes in the monoclinic crystal system, space group C2/c, a = 11.734(2), b = 7.596(1), c = 10.176(1) Å, β = 124.85(1), V = 744.4(2) Å3, Z = 2. The crystal structure was refined to R = 0.065. The average empirical formula is K2.31Ca1.99Cu0.88Al0.04S3.97O16·2H2O. Leightonite is stable up to ∼325°C, and above this temperature it decomposes into high-temperature cubic calciolangbeinite K2Ca2(SO4)3 (P213) and chalcocyanite CuSO4 phases. The thermal expansion coefficients are α11 = 8.3(9), α22 = 3.6(4), α33 = –4.7(5) × 10–6°C–1 at –180°C and α11 = 41.6(5), α22 =36.5(5), α33 = –10.6(1) × 10–6°C–1 at 325°C). [ABSTRACT FROM AUTHOR]

The first aqueous silver borate nitrate Ag3B4O6(OH)2(NO3) has a non-centrosymmetric crystal structure (P43212, a = 10.0196(3) Å, c = 9.2594(2) Å). The compound is prepared by soft hydrothermal synthesis inside an evacuated quartz ampoule. The structure of the resulting 1D–5B-borate compound is formed by [B4O6(OH)2]2– chains consisting of two triborate rings with a common (2Δ3□:(‹Δ2□›–‹Δ2□›–)∞ tetrahedron and NO3 triangles with silver atoms between the rings. The relationship between the structures of Ag3B4O6(OH)2(NO3), Tl2B4O6(OH)2·2H2O and the kernite Na2B4O6(OH)2·3H2O (also formed by [B4O6 (OH)2]2– chains) is discussed. [ABSTRACT FROM AUTHOR]

The thermal behavior of aqueous sulfate NaHSO4·H2O and the product of its dehydration α‑NaHS-O4 is studied. The studies are carried out using high temperature X-ray diffraction and complex thermal analysis. Based on the data of three experiments, the temperature, nature, and sequence of phase transformations are established: NaHSO4·H2O(30–50°C) → α-NaHSO4(140–180°C) → Na2S2O7 + Na3H(SO4)2. With increasing temperature increasing in the NaHSO4·H2O structure hinge deformations occur at the level of a chain of NaO3(OH)(H2O)2 polyhedra. The anisotropy of thermal expansion is αmax/αmin = 1.9 for NaHSO-4·H2O and αmax/αmin = 1.3 for NaHSO4. [ABSTRACT FROM AUTHOR]

Thermal expansion of SrBi2B2O7 borate was investigated by in situ powder X-ray diffraction in the temperature range from –175 to 25°C. Compositional deformations of Sr1 – xBaxBi2B2O7 solid solutions were calculated. The band gaps for solid solutions were determined by the absorption spectroscopy. A similarity of thermal and compositional deformations has been established. These deformations were compared with the crystal structure of Sr1 – xBaxBi2B2O7 solid solutions. [ABSTRACT FROM AUTHOR]

This article presents the results of the interpretation and refinement of the crystal structure of an Sr0.5Ba0.5Bi2O(BO3)2 solid solution. The distribution of cations over positions is refined, which shows that Sr is included in the smallest positions M3 and M1, Ba is in positions M1 and M2, and Bi is found in all three large cationic positions. The crystal structure of Sr0.5Ba0.5Bi2O(BO3)2 is compared with the end members of the series of SrBi2O(BO3)2 and BaBi2O(BO3)2 solid solutions. [ABSTRACT FROM AUTHOR]

Crystals of a novel hybrid organo-inorganic borate, K[B5O6(OH)4][B(OH)3]2(H2O)(C10H20O5)2 (1), were obtained from aqueous solutions and characterized by single-crystal X-ray diffraction and IR spectroscopy. 1 is triclinic (a = 10.1567(4), b = 11.9941(6), c = 17.1893(9) Å, α = 75.280(4), β = 79.406(4), γ = 88.531(4)°, V = 1990.270369 Å3, SG P-1; R1 = 0.058). Its structure contains [K(C10H20O5)2]+ groups which behave as "hydrophobic" templates for the inorganic part comprised of anions and neutral B(OH)3 molecules. [ABSTRACT FROM AUTHOR]

In this study, Ba3Lu(BO3)3 borate obtained by solid-phase synthesis is explored by high-temperature X-ray powder diffraction in the temperature range from 25 to 900°C. At room temperature, the compound expands slightly anisotropically (αmax/αmin = 1.2), and with an increase in temperature, the degree of anisotropy increases significantly (αmax/αmin = 6.9 at 900°C). The maximum expansion is observed along the crystallographic axis c (αc = 10.45 × 10–6°C–1 at 25°C and 36.34 × 10–6°C–1 at 900°C), perpendicular to which the boron-oxygen triangles [BO3] are located, and the minimum is in the plane where the triangles are located. [ABSTRACT FROM AUTHOR]

Hydroxylclinohumite Mg5(SiO4)2(OH,F)2 is a common monoclinic orthosilicate of the humite group, which, on the one hand, is a prototype of promising materials, and, on the other hand, is an important source of information about both the transport and the presence of water in the Earth's mantle, and therefore studying its thermal behavior is of particular interest. In this paper, the mineral is studied by powder X-ray diffraction for the first time in a wide temperature range (–180 ≤ T ≤ 1000°C). The temperature limits for the existence of the phase are established, the principal values of the thermal expansion tensor are calculated, and a structural interpretation of thermal expansion is given. [ABSTRACT FROM AUTHOR]