Space Group R3 Research Articles

Naalasite, NaAl(AsO3OH)2⋅H2O, the Al analogue of nafeasite from the Torrecillas mine, Iquique Province, Chile

AbstractThe new mineral naalasite (IMA2023–027), NaAl(AsO3OH)2⋅H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with anhydrite, juansilvaite, magnesiokoritnigite and a lavendulan-like phase. Naalasite occurs in tightly intergrown aggregates and druses of equant crystals. Crystals are light to medium pink and transparent, with vitreous lustre and white streak. The Mohs hardness is ~3½. The density is 3.19(2) g⋅cm–3. Optically, naalasite is uniaxial (+), with ω = 1.630(3) and ɛ = 1.660(3) (white light). The empirical formula (based on 9 O apfu) is Na0.92Al0.61Fe3+0.39As2O9H4.07. Naalasite is trigonal, space group R32, with cell parameters: a = 8.494(4), c = 26.430(13) Å, V = 1651.5(4) Å3 and Z = 9. The structure, refined to R1 = 3.78% for 641 I > 2σI reflections, is based on a loose 3D framework of alternating AsO3OH tetrahedra and AlO6 octahedra. The structure is topologically equivalent to that of nafeasite and can be regarded as its Al analogue, even though nafeasite is monoclinic with space group C2.

LGYSB:Nd─High-Performance Lasing in the Near-Infrared Region.

Three incongruent melting LawNdxGdyYzSc4-w-x-y-z(BO3)4 (LGYSB:Nd) crystals with different Y concentrations (z = 0.15, 0.05, and 0.025) have been grown by the Czochralski method for the first time. The LGYSB:Nd-type crystals exhibit an acentric structure similar to that of the natural mineral huntite CaMg3(CO3)4, with space group R32. The composition of the LGYSB:Nd_3 (z = 0.025) crystal grown from the starting melt composition La0.628Gd0.547Y0.025Nd0.05Sc2.75(BO3)4 was measured by inductively coupled plasma mass spectrometry method, and it was found to be La0.6794Gd0.4105Y0.0178Nd0.0381Sc2.8542(BO3)4. The transversal spatial distribution of the refractive index in the LGYSB:Nd_3 crystal was investigated. Third-order nonlinear optical susceptibility χ(3) of the LGYSB:Nd_3 crystal was determined from third-harmonic generation experiments with ultrashort (fs) laser pulses. The optical transmission spectrum was measured in the range of 200-2000 nm. The absorption cross-section at 808 nm in σ-polarization was determined to be 1.18 × 10-19 cm2 for the LGYSB:Nd_3 crystal. The 10K absorption spectra revealed that the Nd3+ ions occupy only La3+ cationic sites in the LGYSB host matrix. The emission cross-section at 1064 nm in σ-polarization was determined to be σem(σ) = 1.74 × 10-19 cm2 for the LGYSB:Nd_3 crystal. The fluorescence lifetime was found to be τ = 115 μs for all of the LGYSB:Nd crystals. The LGYSB:Nd_3 laser was operated at an emission wavelength of 1062 nm with very high slope efficiencies of ηsa = 0.74 and ηsa = 0.64 in quasi-cw and cw regimes, respectively.

Nonstoichiometry as a hidden aspect of TbAl3(BO3)4 optical properties.

TbAl3(BO3)4 should not be considered as a strictly stoichiometric compound. A variety of Tb1+xAl3-x(BO3)4 (x = -0.1-0.15) single phase compositions with the R32 space group were synthesized in the TbBO3-(Al2O3·B2O3) system. The K2Mo3O10-B2O3-Al2O3 flux was used to grow Tb1+xAl3-x(BO3)4 (x = 0.06 and 0.09) crystals. The orthoborates have typical luminescence in the green range which correlated with the 5D3 → 7F6 electron transition of Tb3+. However, deviating from stoichiometry can result in halving the quantum efficiency of luminescence. The SHG efficiency from 1064 nm radiation for Tb1+xAl3-x(BO3)4 crystals (x = 0.06 and 0.09) was found to be 1.82 and 1.53 times higher than that of KDP, respectively.

Crystal growth and luminescence properties of TbGa3(BO3)4 crystals

TbGa3(BO3)4 crystals were grown using the Bi2Mo3O12: B2O3 : Tb2O3 flux, which decreases contamination of Bi in the resulting crystal. The produced compound crystallizes in the R32 space group with unit cell parameters: a= 9.4512(4) Å, c=7.4532(2) Å. A strong green emission of the luminescence is primarily dominated by the 5D4 to 7F5 transition in Tb3+. Annealing these crystals in a hydrogen atmosphere at 800°C causes a reduction in the luminescence efficiency. On the other hand, annealing in air results in the increment of QY up to the value of 38%.

Synthesis of LiNi1/3Mn1/3Fe1/3O2 as an Intended Cathode Material for Li-Ion Battery

In the present work, we report the synthesis and characterization of LiNi1/3Mn1/3Fe1/3O2 as cathode material for Li-ion batteries. LiNi1/3Mn1/3Fe1/3O2 was synthesized using a very simple and low-cost sol-gel method and subsequent annealing treatment. The Structural, morphological, and electrochemical performance of the synthesized materials is investigated using X-ray diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron microscopy (FE-SEM), Cyclic voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance spectroscopy (EIS), respectively. The XRD results revealed the formation of layer structure with a pure α-NaFeO2 hexagonal phase, space group R3¯m. Moreover, these results show negligible cation mixing, which suggests well order layer structure. Raman spectrum of the synthesized sample shows structural fingerprints at 609 and 503 cm-1, which also confirms the R3¯m space group. Raman results support the XRD results. The non-uniform microsphere-like morphology with an average particle size of around 200-300 nm was revealed using FE-SEM. The electrochemical properties of the synthesized products were evaluated in rechargeable Li-ion half cells using a non-aqueous organic electrolyte (1 M LiPO4). The cyclic voltammetry shows that redox reactions occur at the surface of the electrode, which is attributed to Mn3+/Mn4+ and Fe3+/Fe4+. The EIS of LiNi1/3Mn1/3Fe1/3O2 exhibits a lower charge transfer resistance, which indicates a shorter path to move the ions. Further, the electrochemical performance of the synthesized material will be discussed in detail.

Spectroscopic investigation of K5La(MoO4)4:Sm3+ red phosphor with excellent thermal stability and color purity for white LEDs

In this study, a series of innovative red-emitting Sm3+-doped K5La(MoO4)4 phosphors were synthesized using the solid-state reaction method. The X-ray powder diffraction patterns and Rietveld refinement confirmed the single-phase structure of the synthesized K5La(MoO4)4:Sm3+ samples with trigonal system (space group R3‾m (#166)). The phosphors demonstrated a strong red emission at 644 nm, corresponding to the electric dipole transition 4G5/2 → 6H9/2 of Sm3+ ions. The optimal doping concentration for K5La(1-x) (MoO4)4:xSm3+ was found to be approximately 5 mol%. The temperature-dependent emission of phosphors was examined and found that the luminescence intensity remained at 86 % even at 480 K, showing the exceptional thermal stability of this material. K5La(1-x) (MoO4)4:xSm3+ phosphors displayed remarkable color stability with chromaticity coordinates falling within the red region in 1931 CIE diagram. K5La(MoO4)4:5 mol%Sm3+ exhibited a high color purity of 99.9 % and internal quantum efficiency (IQE) was measured as 66.8 %. Light-emitting diodes (LEDs) were constructed using InGaN chips and the synthesized red phosphors. The chromaticity coordinates of the fabricated w-LED (white light-emitting diode) were (0.330, 0.351), closely resembling the typical white point of the National Television System Committee (NTSC) at (0.333, 0.333). The color rendering index (CRI, Ra) and correlated color temperature (CCT) of w-LED were 87 and 5627 K. These findings strongly suggest the potential use of K5La(MoO4)4:Sm3+ phosphors as red phosphors in LEDs.

K5Eu1-xHox(MoO4)4: Structures and luminescence properties

The palmierite-type matrix with lanthanides is capable of producing customizable multicolored emission, and has characteristics such as long service life and high energy efficiency. This research explored the impact of synthesis method and composition on structural and luminescence properties of K5Eu1-xHox(MoO4)4 with the palmierite-type structure. Two modifications with space group (SG) R3¯m (α- phase) and C2/m (β-phase) were observed and characterized. This study underscores the critical role of co-doping of Eu3+ and Ho3+ cations in manipulating charge transfer and luminescence efficiency in visible and IR region. The existence of 5D0→7F0 transition in the PL spectra indicates stable local environment of Eu3+ cations regardless of synthesis conditions.

Comprehensive comparisons of crystal structure, Hirshfeld surface and thermochemical properties of two succinic acid metal complexes [LiC2H2O2]2(s) and [NaC2H2O2·3H2O]2(s)

In this work, two aqueous and nonaqueous metal complexes of succinic acid were synthesized, namely Li-succinate (CCDC: 2284044) and hexahydrate Na-succinate (CCDC: 2296979). Their crystal structures were determined by single crystal X-ray crystallography. The Li-succinate crystallizes in trigonal space group R3¯ and the hexahydrate Na-succinate in triclinic P1¯. The Hirshfeld surfaces and the corresponding 2D fingerprints of the two complexes were recorded, showing that the nature of the intermolecular interactions between Li-succinate are mainly coordination bonds and that the intermolecular interactions between hexahydrate Na-succinate are mainly intermolecular hydrogen formation. The experimental heat capacities of the two complexes in the low-temperature interval were determined using a precise automatic adiabatic calorimeter, and the polynomial equations for the variation of the heat capacities with the folding transition temperature were obtained by fitting the measured experimental heat capacities using the least squares method, on the basis of which the values of their Sulpine heat capacities at intervals of 5 K in the low temperature interval and the values of their thermodynamic functions with respect to 298.15 K were calculated. The TG/DSC curves also reveal the molecular structure of the title complexes.

Structural stability and polarization analysis of rhombohedral phases of HfO2

Since the experimental observation of a rhombohedral phase of hafnium oxide, there remains controversy over whether this phase belongs to the R3 or R3m space group. Moreover, the origin of polarization in these two rhombohedral phases has not been comparatively elucidated. Here, we present a theoretical study comparing the relative stability and ferroelectricity of the R3 and R3m phases of HfO2, representing two potential forms of heavily Zr-doped ferroelectric thin films of hafnia found recently. We comprehensively investigate their structural stability and polarization response under in-plane compressive strain. A phase transition from R3 to R3m is discovered under biaxial compressive strain. The direction and magnitude of polarization in both phases can be tuned by strain. Through symmetry mode analysis, we elucidate the improper nature of ferroelectricity. These findings may advance understanding of ferroelectricity in hafnia thin films.

A new mineral cuprodobrovolskyite Na4Cu(SO4)3 from the Tolbachik volcano (Kamchatka, Russia) and relationships in the family of natural anhydrous Na–Cu sulfates

AbstractA new mineral cuprodobrovolskyite, ideally Na4Cu(SO4)3, was found in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with petrovite, saranchinaite, euchlorine, krasheninnikovite, langbeinite, calciolangbeinite, anhydrite, sanidine, tenorite and hematite. Cuprodobrovolskyite occurs as coarse hexagonal tabular or equant, typically skeletal crystals up to 1 mm and their clusters or crusts up to 1.5 cm × 2.5 cm in area. The mineral is transparent, light blue or greenish-bluish to almost colourless with vitreous lustre. Cuprodobrovolskyite is optically uniaxial (+) with ω = 1.509(3) and ε = 1.528(3). The empirical formula calculated on the basis of 12 O apfu is (Na3.64K0.09Pb0.03)Σ3.76(Cu0.51Ca0.22Mg0.16Zn0.07Al0.01Mn0.01)Σ0.98S3.04O12. The unit-cell parameters of cuprodobrovolskyite calculated from the powder X-ray diffraction data are: a = 15.702(2), c = 22.017(5) Å, V = 4701.0(2) Å3, space group R3 and Z = 18. The crystal structure was studied using the Rietveld method, Rp = 0.0246, Rwp = 0.0325, R1 = 0.0521 and wR2 = 0.0770. Cuprodobrovolskyite is an isostructural analogue of dobrovolskyite Na4Ca(SO4)3 with Cu prevailing over Ca. One of the main features of cuprodobrovolskyite is Cu2+ in 7-fold coordination. On the basis of relationships with saranchinaite Na2Cu(SO4)2 and petrovite Na12Cu2(SO4)8 in the Arsenatnaya fumarole and the results of heating experiments, cuprodobrovolskyite is considered as the highest-temperature phase among anhydrous Na–Cu sulfate minerals.

Effect of A-site ionic disorder on structure, magnetic and magnetocaloric properties of La0.85-xNdxAg0.15-yKyMnO3 manganites

In this paper, the effect of A-site ionic disorder (σ2) on the structure, magnetic and magnetocaloric properties in La0.85-xNdxAg0.15-yKyMnO3 have been investigated. X-ray diffraction analysis using Rietveld refinement shows that the crystal structure of the perovskite manganites changes from rhombohedral (space group R3 ͞C) to orthorhombic (space group Pnma) structure with the increasing in σ2. Magnetization measurements showed that, upon increasing σ2, ferromagnetic double exchange interaction of the perovskite manganites diminishes, and as a result, Curie temperature (TC) of the samples decrease linearly. The inverse of susceptibility shows a downturn with decreasing temperature before TC indicating the existence of the Griffiths phase for La0.62Nd0.23Ag0·099K0·051MnO3 (σ2 = 0.004). The magnetic phase transitions of all the samples are belongs to second order transition.

Architecture of new {Ca, Eu, Yb}4CuMg complex intermetallics based on polyicosahedral clusters

The crystal structures of R4CuMg (RCa, Eu, Yb) complex intermetallics, solved by single crystal X-ray diffraction, were found to represent a new trigonal prototype (hR144-h7c2ba, space group R3‾m), being the first examples of 4:1:1 rare earth-rich phases not crystallizing as cF96-Gd4RhIn, adopted by more than 200 compounds known so far. The divalent character of the R component, together with Cu atomic size could contribute to explain the observed structural peculiarity.Indeed, the occurrence of fragments typical of compositionally similar compounds, namely Cu-centered trigonal prisms and Mg-centered core-shell polyicosahedral clusters with R at vertices, prompted a search for significant structural relationships. In this work, a description of the rhombohedral R4CuMg crystal structure is proposed as a linear intergrowth along the c-direction of the two types of slabs R9.5CuMg3.5 (parent type: hP28-kh2ca, SG 194) and R13Cu6Mg (parent type: hR60-b6a2, SG 160). The ratio of these slabs in the studied structure is 2:1, corresponding to the simple equation 6×R9.5CuMg3.5+3×R13Cu6Mg = 24×R4CuMg, normalized to the unit cell content.According to the proposed description, symmetry properties of the slabs (depicted by the p3m1 layer group) were used for screening of possible space groups for other potential members of the same/similar intergrowth families.

Li4Ln[PS4]2Cl: Chloride-Containing Lithium Thiophosphates with Lanthanoid Participation (Ln = Pr, Nd and Sm)

The synthesis and structural analysis of three new chloride-containing lithium thiophosphates(V) Li4Ln[PS4]2Cl with trivalent lanthanoids (Ln = Pr, Nd and Sm) are presented and discussed. Single crystals of Li4Sm[PS4]2Cl were obtained and used for crystal structure determination by applying X-ray diffraction. The other compounds were found to crystallize isotypically in the monoclinic space group C2/c. Thus, Li4Sm[PS4]2Cl (a = 2089.31(12) pm, b = 1579.69(9) pm, c = 1309.04(8) pm, β = 109.978(3)°, Z = 12) was used as a representative model to further describe the crystal structure in detail since Li4Pr[PS4]2Cl and Li4Nd[PS4]2Cl were confirmed to be isotypic using powder X-ray diffraction measurements (PXRD). In all cases, a trigonal structure in the space group R3¯ (e.g., a = 1579.67(9) pm, c = 2818.36(16) pm, c/a = 1.784, Z = 18, for Li4Sm[PS4]2Cl) displaying almost identical building units worked initially misleadingly. The structure refinement of Li4Sm[PS4]2Cl revealed bicapped trigonal prisms of sulfur atoms coordinating the two crystallographically distinct (Sm1)3+ and (Sm2)3+ cations, which are further coordinated by four anionic [PS4]3− tetrahedra. The compounds also contain chloride anions residing within channel-like pores made of [PS4]3− units. Eight different sites for Li+ cations were identified with various coordination environments (C.N. = 4–6) with respect to chlorine and sulfur. EDXS measurements supported the stoichiometric formula of Li4Ln[PS4]2Cl, and diffuse reflectance spectroscopy revealed optical band gaps of 2.69 eV, 3.52 eV, and 3.49 eV for Li4Sm[PS4]2Cl, Li4Nd[PS4]2Cl, and Li4Pr[PS4]2Cl, respectively. The activation energy for Li+-cation mobility in Li4Sm[PS4]2Cl was calculated as Ea(Li+) = 0.88 eV using BVEL, which indicates potential as a Li+-cation conductor.

Photoluminescence, structural and antibacterial properties of co-doped β-Ca3(PO4)2-type phosphates Ca8CuRE(PO4)7 (RE = Eu–Er)

Novel Ca8CuRE (PO4)7 where RE3+ = Eu3+, Tb3+, Dy3+, Ho3+ and Er3+ were synthesized by a solid-state method in air. The structures of the samples were characterized by powder X-ray diffraction using Rietveld refinement to determine the occupation of crystal sites. The samples are found to have a centrosymmetric structure with space group R3¯c, as shown by dielectric measurements. These synthesized Ca8CuRE(PO4)7 samples have multifunctional properties. The Cu2+ ions provide antibacterial properties, while the rare earth elements ions exhibit luminescence properties, and the β-Ca3(PO4)2-type host is biocompatible. The photoluminescence properties of RE3+ ions were studied and compared with other simmilar Ca8MRE(PO4)7 phosphates, where M is a divalent metal. The photoluminescence intensity quenching in terms of energy transfer from RE3+ to Cu2+ is disscused. The bioactive properties were studied in relation to antibacterial activity against E. coli and S. aureus. All syntesized Ca8CuRE(PO4)7 samples demonstrate very high and stable inhibition of bacteria growth. The correlation between crystal structure and properties is discussed. By combining multiple approaches to the directional design of such materials, several important properties within a single chemical compound to achieve biovisualization and bioactive properties simultaneously can be combined.

Weak ferromagnetism in a diamagnetically diluted sublattice of Fe3+ ions in solid solutions Y2 −x Fe1 +xTaO7 (x = 0 –0.2) with pyrochlore-like structure

A series of layered solid solutions Y2-xFe1+xTaO7 (x = 0–0.2) was synthesized and a structural transition (space group R3¯ ↔ space group P3121) was observed at x = 0.1. In Y2−xFe1+xTaO7, which belongs to both structural types, geometrically frustrated 2D sublattices of kagome-type are formed, in which Fe3+ ions are coupled by short-range antiferromagnetic interactions, and the transition to the spin glass state is observed at Tg ∼ 4.3 K. A phenomenon of weak ferromagnetism has been detected, the cause of which is probably a small tilt of the Fe3+ spins due to the Dzyaloshinskii–Moriya antisymmetric superexchange.

The morphology and electrochemical properties of LiNi0.8Co0.1Mn0.1O2 cathode material prepared by the assistance of CTAB surfactant

The effect of hexadecyl trimethyl ammonium bromide (CTAB), as a surfactant, on morphology and electrochemical properties of LiNi0.8Co0.1Mn0.1O2 cathode materials was systematically investigated. Ni0.8Co0.1Mn0.1(OH)2 precursors were obtained through co-precipitation method using CTAB as a surfactant, then sintered with lithium salt to synthesize LiNi0.8Co0.1Mn0.1O2 cathode materials. XRD and TEM results show that the materials possess rhombohedral α-NaFeO2 layered structure (space group R3¯m), and Ni/Li mixing degrees reduce and the (003) crystal plane spacing enlarges to some degree upon the assistance of CTAB. SEM images prove that the formation of columnar primary particles of can be promoted by the assistance of CTAB. The discharge capacity for the samples reaches the maximum 186.9 mAh∙g−1 at 0.1C while the content of CTAB increases to 0.2%, and NCM 0.2 sample also shows better high-rate charge/discharge ability and preferable cycling performance. Furthermore, NCM 0.2 sample exhibits lower charge transfer impedance and faster diffusion rate of Li+ than that of the blank.

Study of the Electronic Band Structure and Structural Stability of Al(CN)2 and Si(CN)2 by Density Functional Theory

By substituting the A site in P21/c-A(CN)2 and varying the lattice parameters a, b, c, and the unit-cell angles, along with using crystal graph convolutional neural networks to calculate their cohesive energy, the candidate compounds, Al(CN)2 and Si(CN)2, were selected from the structure with the lowest cohesive energy. The two candidate structures were then optimized using first-principles calculations, and their phonon, electronic, and elastic properties were computed. As a result, two dynamically stable structures were found: Al(CN)2 with a space group of Cmcm and Si(CN)2 with a space group of R3¯m. Their phonon spectra exhibited no imaginary frequencies; thus, their elastic constants satisfied the mechanical stability criteria. Structurally, Si(CN)2 is similar to 6H-SiC and 15R-SiC. Its elastic constants indicated that it is harder than those SiC materials. Al(CN)2 exhibits metallic properties and the indirect wide-bandgap of Si(CN)2 was calculated by the generalized gradient approximation, the local density approximation, and the screened hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE06) is found to be 3.093, 3.048, and 4.589 eV, respectively. According to this wide bandgap, we can conclude that Si(CN)2 has the potential to be used in high-temperature and high-power environments, making it usable in a broad range of applications.

A Surprising Example of Crystal Structure Retention for 3,5-Di-(tert-butyl)-2-hydroxyazobenzene Ligand during the Formation of Ni(II) and Pd(II) Complexes

The structures of 3,5-di-(tert-butyl)-2-hydroxyazobenzene (L) in the free state and in complexes with Ni2+ (I) and Pd2+ (II) cations are studied by X-ray diffraction (XRD). The same space group R3¯с with close unit cell parameters, the same crystal structure motif, and unusual conformations of the cupola-shaped coordination polyhedra of complexes I and II are revealed by XRD for ligand L. In complexes I and II based on this compound as the ligand, the coordinating atoms form trans-planar coordination nodes.

New Halide-Based Sodium-Ion Conductors Na3Y2Cl9 Inversely Designed by Building Block Construction.

Due to the excellent ionic conductivity and compatibility with high-voltage cathodes, halide-based superionic conductors as promising electrolytes have received widespread attention. A series of halide-based conductors, including Na3YCl6, are investigated aiming to find new solid electrolytes for sodium-ion batteries. However, Na3YCl6 with high ionic conductivity is meta-stable in thermostability while the stable phase exhibits poor ionic transport properties. In this work, we find that the coplanar formed anionic group (Y2Cl9)3- is the result of a combination of the structural features of the fast ion phase and stable phase of Na3YCl6 by systematic analysis of crystal structures. Aiming to find fast sodium-ion conductors, the three-step structure construction method using functional (Y2Cl9)3- groups as building blocks is proposed, and three new crystal structures in the composition of Na3Y2Cl9 with the space group of P63, Cc, and R32 are obtained. Na+ transport properties, thermostability, and electrochemical window of these structures with various symmetries are investigated by first-principles calculation methods. The results show that the principle to inverse design crystal structures of halides by basic blocks, e.g., anion groups and mobile cations, is proven to be effective and successful. For P63-Na3Y2Cl9 with outstanding transport properties, the simulation results indicate that its superionic behavior is attributed to the coherent diffusion connecting two directions. The synchronization of the migration pathways along the ab plane and the migration pathways along the c direction promotes the Na ion conductivity in Na3Y2Cl9. Our research will promote the understanding of the transport mechanism in halide-based electrolytes, and the structure construction method based on functional basic building blocks and special stacking modes will accelerate the inverse design of inorganic crystal structures.

Synthesis, structural and spectroscopic investigations of dolomite-type MSn(BO3)2 with M = Mn, Fe, Co and Ni

Abstract Dolomite-type MSn(BO3)2 phases for M = Mn, Fe, Co and Ni have been synthesized using solid-state synthesis carried out in sealed quartz tubes. X-ray powder diffraction data Rietveld refinements confirm the rhombohedral space group R 3 ‾ $R\overline{3}$ for all compositions. The change in unit-cell parameters follows the increasing nature of the radius of the M-cations. Both the MO6 and SnO6 octahedra are found to be quite regular. 119Sn Mössbauer spectroscopy investigations complement the almost undistorted nature of the SnO6 octahedra and the tetra-valent charge of the tin-atoms. Detailed vibrational features are described from the Raman and the FTIR spectral data collected at ambient conditions. The frequency shifts of some selective Raman and IR bands are explained in terms of the change of cationic sizes and the respective M–O bond distances. The UV/Vis diffuse reflectance data are analyzed using the RATD method, leading to direct bandgaps for all the investigated samples. The wide bandgap semiconductors (3 – 4 eV) show increasing transition energies with increasing cation sizes of the high-spin M-cations in the dolomite types.