Measurement of Ambient NH<Subscript>3</Subscript>, NO and NO<Subscript>2</Subscript> at an Urban Area of Kolkata,India

Mixing ratios of ambient NH₃, NO and NO₂ were measured in campaign mode at Kolkata a megacity of Indo-Gangetic plain of India to study the diurnal variation and mixing ratios of NH₃, NO and NO₂ during 24–27 February 2012. The present study has been carried out on campaign based measurement of mixing ratios of NH₃, NO and NO₂ for short period of time at Kolkata represent the indicative values over the region. The average mixing ratios of ambient NH₃, NO and NO₂ were recorded as 43.4 ± 7.0 ppb, 46.0 ± 8.7 ppb and 31.9 ± 5.5 ppb at Kolkata. In the present case, significant diurnal variation of NH₃, NO and NO₂ were recorded at Kolkata during study. Mixing ratio of ambient NH₃ reaches its maxima (78.9 ppb) at night and minimum during daytime. Result reveals that the ambient NH₃ mixing ratio is positively correlated with ambient NO (r ² = 0.395) and NO₂ (r ² = 0.404) mixing ratio and significant negatively correlated with ambient temperature (r ² = –0.669). Surface wind direction and wind speed analysis indicates that the local acitivities (livestock, drainage, agriculture, vehicles etc.,) may be the possible sources of ambient NH₃ at the observational site of Kolkata.     

Measurements of Particulate (PM2.5), BC and Trace Gases Over the Northwestern Himalayan Region of India

Ambient trace gases (NH₃, NO, NO₂ and SO₂) and black carbon (BC) were measured along with particulate matter (PM_2.5) over the northwestern Himalayan region (Palampur, Kullu, Shimla, Solan and Nahan) of Himachal Pradesh (HP), India in a campaign mode during 12–22 March 2013 to evaluate the ambient air quality of the region. The average mixing ratio of ambient NH₃, NO, NO₂ and SO₂ were recorded as 7.1 ± 2.6, 3.1 ± 1.3, 3.9 ± 1.4 and 1.7 ± 0.7 ppb respectively over the northwestern Himalayan region. The average concentration of BC was estimated as 2.2 ± 0.5 µg m^?3 over the region whereas average concentration of PM_2.5 mass was estimated as 41.8 ± 7.9 µg m^?3. The spatial variation of ambient trace gases (NH₃, NO, NO₂ and SO₂), BC and PM_2.5 over the northwestern Himalayan region, India reveals that the region is mainly influenced by local activities, i.e., tourism activities, agricultural activities, biomass burning and vehicular emission. A significant positive linear correlation of NH₃ and NH₄ ⁺ with SO₄ ^2?, NO₃ ^? and Cl^? (NH₄ ⁺ vs. SO₄ ^2? , r ² = 0.652; NH₄ ⁺ vs. NO₃ ^?, r ² = 0.701; and NH₄ ⁺ vs. Cl^?, r ² = 0.627) of the PM_2.5 indicates the possible formation of (NH₄)₂SO₄, NH₄NO₃ and NH₄Cl aerosols over the region.     

Long-Term Measurements of SO 2 Over Delhi,India

Long-term measurements (2011–2018) of ambient sulphur dioxide (SO2) and meteorology were carried out at an urban site of Delhi, India, to study the seasonal and inter-annual variations of SO2 over Delhi. The average mixing ratio of SO2 was estimated as 2.26 ± 0.48 ppb for the entire study period. Mixing ratio of ambient SO2 was estimated as 2.19 ± 0.64 ppb, 2.07 ± 0.89 ppb, 2.49 ± 1.05 ppb and 2.27 ± 0.71 ppb during winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. SO2 mixing ratio was recorded maxima during monsoon (2.49 ± 1.05 ppb) season, whereas minima during pre-monsoon season (2.07 ± 0.89 ppb). The mixing ratio of SO2 showed slightly increase in the trend during observational period. Surface wind speed and wind directions analysis indicates the influence of local sources on the mixing ratio of SO2 at the study site. Backward trajectories and potential source contributing factor (PSCF) analysis also showed the local as well as the regional sources (industrial activities, coal burning and thermal power plants etc.,) influencing the mixing ratio of SO2 over Delhi.     

Study on Ambient Air Quality of Megacity Delhi,India During Odd–Even Strategy

State Government of Delhi had adopted odd–even scheme on vehicles plying in megacity Delhi to understand and improve the air quality of Delhi. To understand the effect of odd–even scheme on the concentration of pollutants, we have analysed the concentrations of chemical constituents [organic carbon, elemental carbon, water soluble inorganic components, trace elements and stable carbon and nitrogen isotopic composition (δ¹³C_TC) and N (δ¹⁵N_TN)] of PM_2.5 and PM₁₀ along with mixing ratios of trace gases (NO _x , CO, SO₂ and NH₃) data collected at an urban site of megacity Delhi during first phase (Phase-I: winter 2016) and second phase (Phase-II: summer 2016). During the Phase-I of the scheme, mass concentrations of PM_2.5 and PM₁₀ were changed by ?13 and ?5%, respectively, whereas, concentrations of PM_2.5 and PM₁₀ were changed by +18 and +16%, respectively during the Phase-II as compared to before the implementation of the scheme. The analysis of chemical constituents of PM_2.5 and PM₁₀ reveals that the odd–even strategy marginally changed the concentrations (markers) of vehicular emission. During both the phases, mixing ratios of trace gases (NO _x , CO, SO₂ and NH₃) were reduced non-significantly during the odd–even scheme as compared to before the implementation of the scheme.     

Atmospheric Fine and Coarse Mode Aerosols at Different Environments of India and the Bay of Bengal During Winter-2014: Implications of a Coordinated Campaign

In this paper, we present mass concentrations of particulate matter [PM_2.5, PM₁₀ size fractions and total suspended particulates (TSP)] measured simultaneously over land stations (Kullu, Patiala, Delhi, Ajmer, Agra, Lucknow, Varanasi, Giridih, Kolkata, Darjeeling, Jorhat, Itanagar, Imphal, Bhubaneswar, and Kadapa), mostly distributed across the Indo-Gangetic plain (IGP) of India as well as in the marine atmosphere over Bay of Bengal (BoB) in the period from 20 January to 3 February, 2014. The main objective of this study was to quantify the continental outflow of particulates (PM_2.5, PM₁₀ and TSP) from IGP and associated regions into the BoB along with low level north-east wind flow during winter monsoon period. The present study provides a glimpse of the aerosol loading over the IGP region. During this campaign, the highest average PM_2.5 (187.8 ± 36.5 µg m^?3, range 125.6–256.2 µg m^?3), PM₁₀ (272.6 ± 102.9 µg m^?3, range 147.6–520.1 µg m^?3) and TSP (325.0 ± 71.5 µg m^?3, range 220.4–536.6 µg m^?3) mass concentrations were recorded at Varanasi, Kolkata and Lucknow over middle and lower IGP regions. The PM_2.5 (average 41.3 ± 11.9 µg m^?3; range 15.0–54.4 µg m^?3), PM₁₀ (average 53.9 ± 18.9 µg m^?3; range 30.1–82.1 µg m^?3) and TSP (average 78.8 ± 29.7 µg m^?3; range 49.1–184.5 µg m^?3) loading over BoB were found to be comparable to land stations and suggests possible continental outflow. Over the continental region, the highest PM_2.5/PM₁₀ ratio was recorded at Delhi (0.87). The PM_2.5/PM₁₀ ratio over BoB (0.77) was found to be quite high and comparable to Varanasi (0.80) and Agra (0.79).     

Synthesis and crystallographic study of Pb-Sr hydroxyapatite solid solutions by high temperature mixing method under hydrothermal conditions

The solid solutions in the system of Pb and Sr hydroxyapatite, Sr_10−xPb_xHAp (x = 0-10), were successfully synthesized by high-temperature mixing method (HTMM) at 160 °C for 12 h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice constants, both a and c, of the solid solutions varied linearly with Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M(2) site in the apatite structure. HTMM gives Sr-Pb HAp solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb₃O₂(OH)₂ in the Pb(NO₃)₂·4H₂O solution before mixing with (NH₄)₂HPO₄ solution at 160 °C, HTMM causes the decrease of crystallization of the samples with high Pb content.     

Study of C<Subscript>2</Subscript>–C<Subscript>5</Subscript> Non-methane Hydrocarbons and Their Ozone Formation Potential at Bhubaneswar,an Eastern Coastal Site in India

A preliminary study has been taken up to evaluate the NHHCs concentration and their effect on atmospheric chemistry at Bhubaneswar for the very first time during winter months when pollution load is prevalent. For this purpose ambient air samples were collected during a period of 3 months (Dec 2013–Feb 2014). The samples were analyzed for C₂–C₅ light non-methane hydrocarbons (NMHCs) using a gas chromatograph with a thermal desorption system. It was observed that level of NMHCs over the measurement site was lower in comparison to other urban locations within India but higher in comparison to Bay of Bengal. Statistical interpretation suggests a non-significant variation of NMHCs concentration between the observation months. Diurnal observations revealed a higher concentration of both n-pentane and i-pentane which was mostly attributed to solvent evaporation. Liquefied petroleum gas usage is believed to be a major contributor to the mixing ratios of propane (1.5 ppbv) and butane (0.027 ppbv) while ethane and ethylene emissions were attributed to traffic volume and vehicular exhausts. The propylene-equivalent and ozone formation potential of NMHCs have also been calculated in order to find out their OH reactivity and contribution to the photochemical ozone formation. Relative humidity was also observed to have a significant correlation with NMHCs concentration. Variation of total non-methane hydrocarbons (TNMHCs) with ozone and CO suggest the role of TNMHC as precursor for ozone formation.     

Doping mechanisms and electrical properties of bismuth tantalate fluorites

Phase-pure bismuth tantalate fluorites were successfully prepared via conventional solid-state method at 900 °C in 24–48 h. The subsolidus solution was proposed with the general formula of Bi_3+x Ta_1?x O_7?x (0 ≤ x ≤ 0.184), wherein the formation mechanism involved a one-to-one replacement of Ta⁵⁺ cation by Bi³⁺ cation within ~4.6 mol% difference. These samples crystallised in a cubic symmetry, space group Fm-3 m with lattice constants, a = b = c in the range 5.4477(± 0.0037)–5.4580(± 0.0039) Å. A slight increment in the unit cell was discernible with increasing Bi₂O₃ content, and this may attribute to the incorporation of relatively larger Bi³⁺ cation in the host structure. The linear correlation between lattice parameter and composition variable showed that the Vegard’s law was obeyed. Both TGA and DTA analyses showed Bi_3+x Ta_1?x O_7?x samples to be thermally stable as neither phase transition nor weight loss was observed within ~28–1000 °C. The AC impedance study of Bi₃TaO₇ samples was performed over the frequency range 5–13 MHz. At intermediate temperatures, ~350–850 °C, Bi_3+x Ta_1?x O_7?x solid solution was a modest oxide ion conductor with conductivity, ~10^?6–10^?3 S cm^?1; the activation energy was in the range 0.98–1.08 eV.     

Effects of BaNb2O6 addition on microstructure and dielectric properties of BaTiO3 ceramics

(1 ? x)BaTiO₃–xBaNb₂O₆ [(1 ? x)BT–xBN] ceramics with x = 0, 0.005, 0.008, 0.01, 0.02, 0.03 were prepared by a conventional solid-state reaction route. The effect of BN addition on phase composition, microstructure and dielectric properties of BT-based ceramics were investigated by X-ray diffraction, scanning electron microscope and impedance spectroscopy. The results showed that a systematic structure change from the ferroelectric tetragonal phase to pseudo-cubic phase was observed near x = 0.01 at room temperature. It resulted in a considerable change of density, grain size and dielectric properties of the samples when BN was introduced. Meanwhile, it also lowered the sintering temperature of the ceramics. The dielectric constant peak and the variation rate of capacitance at Curie temperature are markedly depressed and broaden with increasing BN content. Especially, the ceramics with x = 0.008 and x = 0.01 showed good dielectric properties over the measured temperature range. Optimal dielectric properties of ε = 3,851, tanδ = 0.7 % at room temperature and Δε/ε₂₅ ≤ ±6.8 % (?55 to 125 °C) were obtained for the BT-based ceramics doped with 0.8 mol% BN, which was obviously superior to BaTiO₃ and BaNb₂O₆ ceramic, and it met the requirements of EIA X7R specifications.     

Effect of Ultrafast Thermal Quenching on the Transport and Magnetotransport Properties of Nd0.67Sr0.33MnO3

We report on the results of ultrafast quenching of Nd_1?x Sr _x MnO₃ (x=0.33) from 1200 °C down to ?196 °C in a fraction of a second, at ambient pressure. Transport measurements showed a 27 K shift in the metal-insulator transition (MIT) temperature of the quenched sample compared to the as-grown sample. We found that ultrafast quenching significantly widens the temperature range of the magnetoresistance (MR) from few degrees to over 200 K. These changes are attributed to induced stress and change in grain size, which X-Ray analysis and SEM measurement have confirmed. X-Ray measurements confirms the presence of single phase in both the slowly-cooled and ultrafast-cooled samples.     

Structure and dielectric properties of Nd x Sr1−x TiO3 ceramics for energy storage application

Polycrystalline Nd-doped SrTiO₃ ceramics with the formula Nd _x Sr_1?x TiO₃ (NSTO, x = 0, 0.024, 0.056, 0.104, 0.152, 0.200) were prepared by solid state reaction route. X-ray diffraction (XRD) analysis confirmed the formation of monophasic compounds and indicated the structure to be changed from cubic to tetragonal by increasing Nd doping concentrations. A remarkable decrease in grain size from ~30 μm for un-doped SrTiO₃ ceramics to ~1 μm for Nd-doped SrTiO₃ ceramics with x = 0.024 was observed by scanning electron microscopy. The grain size had a degree of increasing with further increasing Nd doping concentration and reached ~3 μm when the x value was 0.200. The dielectric properties of NSTO ceramics were measured at 1 kHz in ambient temperature. It revealed that the dielectric constant dramatically increases for the reason of Nd doping, leading to a maximum value of 19,800 for as-sintered sample with x = 0.104. The breakdown strength of all Nd-doped SrTiO₃ samples was found to be higher than 10 kV/mm. The relationship between dielectric properties and the microstructure feature, as well as the defect structures correlated with the charge compensation induced by trivalent Nd³⁺ doping, was discussed tentatively.     

Highly sensitive free-base-porphyrin-based thin-film optical waveguide sensor for detection of low concentration NO<Subscript>2</Subscript> gas at ambient temperature

Meso-5,10,15,20-tetrakis-(4-tertbutyl phenyl) porphyrin was synthesized using Adler–Longo method and was served as sensing material. Electronic absorption spectra of the porphyrin chloroform solution and its thin film were studied comparatively. An optical waveguide sensor based on free-base porphyrin was fabricated by spin coating method. Absorption variation of porphyrin film was studied before and after exposure to NO₂, H₂S, SO₂, and volatile organic gases. XRD patterns of porphyrin film before and after exposure to analytes (NO₂, SO₂, and H₂S) were provided, and light source of the OWG testing system was selected. This facile-prepared sensor exhibited high sensitivity and selectivity to NO₂ with fast response time of 3 s and slow recovery time of 10 min or so and was capable of measuring NO₂ down to 10 ppb at ambient temperature. Scanning electron microscopy was employed to characterize film morphology before and after contact with NO₂. Film thickness was measured before (71.3 nm) and after (76.8 nm) exposure to NO₂, and film thickness variation value (5.20 nm) was calculated. The sensing behavior of the studied sensing device was tested through mixture of H₂S, SO₂, and VOC gases with NO₂ and without NO₂ for determination of the selectivity of the device. Film stability was probed by UV–Vis spectra, and response values of sensing element to NO₂ gas were detected after several days of film preparation, and its RSD value was 1.66%.     

Density-controllable growth of SnO2 nanowire junction-bridging across electrode for low-temperature NO2 gas detection

The junction-bridging structure of metal oxide nanowires (NWs) improves gas-sensing properties. In this study, an on-chip growth method was used to fabricate gas sensors, it easily and effectively controls NW junctions. SnO₂ NWs were synthesized by thermal evaporation at 800 °C with tin powder as the source. The density of the NW junctions was controlled by changing the mass of the source material. A source material with large mass yielded high-density NW junctions. With electrode spacing of 20 μm, NW junctions were formed from the source material of larger than 2 mg. Gas sensing results revealed that the junction sensors exhibited a good response to NO₂ gas at a concentration of 1–10 ppm. The sensors exhibited a good response to NO₂ gas at low temperature of up to 100 °C and short response–recovery time (~20 s). The sensors also had good selectivity to NO₂ gas. The response (R _gas /R _air) to 1 ppm NO₂ was as high as 22 at 100 °C, whereas the cross gas responses (R _air /R _gas) to 10 ppm CO, 10 ppm H₂S, 100 ppm C₂H₅OH, and 100 ppm NH₃ were negligible (1.1–1.3).     

Phase transition and piezoelectric properties of (1 − x)K0.5Na0.5NbO3–xLiSbO3 ceramics by hydrothermal powders

KNbO₃, NaNbO₃ and LiSbO₃ powders were synthesized by a hydrothermal route have been used to prepare (1 ? x)K_0.5Na_0.5NbO₃–xLiSbO₃ (KNN–LS; x = 0.00–0.08) ceramics. The effects of LiSbO₃ doping on the structures of KNN–LS ceramics have been systematically investigated by X-ray diffraction (XRD) and Rietveld refined XRD patterns. A gradual phase transition from orthogonal to tetragonal with the increase of LiSbO₃ content is demonstrated. Thereinto, the monoclinic phase is identified for the KNN–LS ceramic with the LiSbO₃ content of x = 0.08. Meanwhile, the XRD pattern reveals that the intensity ratio of (200)/(002) crystal face of the ceramic with x = 0.08 was bigger than one, which is different from the tetragonal phase. The tetragonal phase is revealed in the KNN–LS ceramic in the vicinity of x = 0.07, accompanying with relatively higher piezoelectric and ferroelectric properties. Tetragonal phase is beneficial to improve the piezoelectric properties of the KNN–LS ceramics.     

Kinetics of gas-phase conversion of U<Subscript>3</Subscript>O<Subscript>8</Subscript> into water-soluble compounds in nitrating atmosphere at 25–30°С

The kinetics of the gas-phase conversion of U₃O₈ in NO_x–H₂O (vapor)–air and HNO₃ (vapor)–H₂O (vapor)–air atmospheres was fitted by the Kazeev–Kolmogorov–Erofeev equation. The following parameters n and K were obtained: for experiments in NO_x–H₂O (vapor)–air atmosphere, n = 0.2 ± 0.1 and K = 0.2 ± 0.2 h^–1; for experiments in HNO₃ (vapor)–H₂O (vapor)–air atmosphere, n = 0.3 ± 0.2 and K = 0.03 ± 0.02 h^–1 (confidence probability p = 0.95). For the U₃O₈ conversion in both media, n < 0.5, which suggests the diffusion control of the U₃O₈ conversion under the action of both HNO₃ and NO_x.     

Properties of B-site non-stoichiometric (K0.5Na0.5)(Nb0.9Ta0.1)1+x O3 lead-free piezoelectric ceramics

The non-stoichiometric (K_0.5Na_0.5)(Nb_0.9Ta_0.1)_1+x O₃ (x = 0, ±0.005, ±0.010) [KN(NT)_1+x ] lead-free piezoelectric ceramics were prepared by normal sintering. The samples were characterized by X-ray diffraction and scanning electron microscopy. All the KN(NT)_1+x ceramics possess orthorhombic perovskite structure. The grain growth of the ceramics is inhibited and the relative density is improved with increasing x. 0.5 mol% (NT)⁵⁺ excess KN(NT)_1+x ceramic which sintered at 1,120 °C has the highest piezoelectric performances among with other samples. Meanwhile, the (NT)⁵⁺ excess ceramics have better time stability than the (NT)⁵⁺ deficient ones. These results show that the KN(NT)_1+x ceramic with x = 0.005 is a promising lead-free piezoelectric material.     

Preparation and performance of organic–inorganic halide perovskites

Layered organic–inorganic perovskites have potential application in solar cells because of their unique electrical and optical properties. These materials can also overcome the instability of organic sensitizers and the disorder of metal oxides. A preliminary study on the preparation of organic–inorganic halide perovskites (CH₃NH₃PbI _x Cl_3?x ) was conducted in this paper. The synthesis temperature and thermal stability in air were analyzed by thermogravimetric analysis and differential scanning calorimetry. The structure and morphology of the products were investigated by X-ray diffraction and scanning electron microscopy. UV–visible spectroscopy revealed that the material had good absorption within the range of 350–750 nm and can be used as the active light-absorbing layer of solar cells. Hybrid solar cells of FTO/TiO₂–CH₃NH₃PbI _x Cl_3?x /Spiro-MeOTAD/Ag were found to have a high fill factor of 0.5 but low power conversion efficiency of 0.28 %.     

Influence of calcium and phosphorus release from bioactive glasses on viability and differentiation of dental pulp stem cells

The release of ions that can significantly contribute toward cellular response is an important characteristic of bioactive glasses (BG). Here, ionic extracts of three different compositions of BG powders in 60 mol% SiO₂, x mol% CaO (x = 28, 32 and 36), x mol% P₂O₅ (x = 12, 8 and 4) compositional system were utilized to study their effect on the viability, differentiation and mineralization of dental pulp stem cells (DPSCs) in vitro. ICP was applied to detect the exact ionic concentrations released from different composition of BG. DPSCs treated with conditioned media from the glass with 4 mol% P₂O₅ (BGCM1, media containing 44.01 ± 0.6 mg/L Si, 61.72 ± 0.1 mg/L Ca and 7.57 ± 0.01 mg/L P) were more metabolically active compared to conditioned media from the glass with 8 mol% P₂O₅ (BGCM2, media with 47.36 ± 0.7 mg/L Si, 57.4 ± 0.1 mg/L Ca and 14.54 ± 0.2 mg/L P), at all times tested, but in all cases the process was slower than the control. Cells exposed to media conditioned by the glass with 12 mol% P₂O₅ (BGCM3, 40.46 ± 0.5 mg/L Si, 61. 85 ± 0.3 mg/L Ca and 28.43 ± 0.3 mg/L P) responded differently, such that cells showed to be more metabolically active than control at day 3, but then similar to or lower than control at higher time points. Differentiation of DPSCs toward osteogenic lineage in the presence of BGCM was assessed by Alizarin red staining. Cells treated with high phosphate BGCM3 displayed a higher density of red mineralized nodules than cells treated with BGCM1 and BGCM2 after 21 days of culture in non-osteogenic medium. BGCM3 was therefore chosen for gene expression studies. Osteogenic differentiation of DPSCs in the presence and/or absence of BGCM3 or osteogenic supplements were studied by RT-PCR. Overall, the results demonstrated that, in the absence of osteogenic supplements, BGCM3 group showed a significantly higher mRNA expression levels for alkaline phosphatase at day 7, osteopontin and osteonectin at days 7 and 14, and a high level of collagen I at day 14, compared to negative control group (BM?). Overall, the results obtained from BGCM3 group are beneficial for the design and manufacture of scaffolds or particulates with tailored ion release for a range of bone repair applications.     

Synthesis, characterization, and catalytic activity of nitridated magnesium silicate catalysts

Amorphous and crystalline magnesium silicates (MgSils) were prepared by sol–gel and template-assisted hydrothermal synthesis methods, respectively. The obtained materials were nitridated with NH₃ at 300, 500, and 800 °C for 24 and 48 h generating nitridated MgSil catalysts. The catalysts were characterized by XRD, FTIR, TG–MS, N₂-physisorption, Hammett indicators, and elemental analysis methods. MgSils nitridated at 300 °C were found to be more active for the Knoevenagel condensation reaction, compared to those nitradated at 500 or 800 °C. A larger amount of nitrogen was incorporated in the framework of amorphous MgSil compared to the crystalline MgSil. FTIR analysis indicated the presence of NH _x species, which were known to form upon reaction between NH₃ and M-OH groups. It was also found that the presence of Si–OH and Mg–OH groups along with the basic –NH₂ functional groups is responsible for the enhanced catalytic activity of the low-temperature nitridated catalysts.     

Investigation of earth-alkaline (EA = Mg,Ca, Sr) containing methylammonium tin iodide perovskite systems

Methylammonium tin iodide systems containing earth-alkaline ions (CH₃NH₃Sn_1?x (EA) _x I₃, EA = Ca²⁺, Sr²⁺, Mg²⁺, 0 ≤ x ≤ 0.30) were investigated. The X-ray diffraction patterns detected the formation of tetragonal nearly cubic CH₃NH₃SnI₃ (space group P4mm), SnI₂, and not identified phases. The morphological analysis confirmed the presence of secondary phases with formation of irregularly shaped crystallites. The Sn3d and I3d photoemission spectra revealed the typical position and separation of spin–orbit components for Sn²⁺ in halides. Static thermogravimetric measurements (T = 85 °C) showed a barely measurable weight loss for EA = Mg, a dramatic decrease of the weight loss rate for EA = Ca, and recorded weight losses till t ≈ 1.5 h only for EA = Sr, respectively. The optical spectra displayed absorption edges which increased at increasing the (EA)-content with maximum values for x = 0.050 (λ _on-set = 1754 nm, EA = Mg; λ _on-set = 1692 nm, EA = Ca; and λ _on-set = 1338 nm, EA = Sr, respectively). The Tauc plots revealed a direct semiconducting behavior with band energy gaps depending on the nature and amount of the (EA)-ions. The photoluminescence (PL) spectra showed, for EA = Mg, an increase of the PL-band intensity at increasing the Mg content with a maximum at x = 1.0 and, for EA = Ca, an increase of band intensity at increasing the Ca-content and for EA = Sr, a band intensity maximum at x = 0.025. This was explained by the similar ionic radius between Sn²⁺ and Sr²⁺ ions which can be easily exchanged in the SnI₆ ^2? octahedra.