Ba Substitution Research Articles

Stability studies of [CsxBay][(Al3+,Ti3+)2y+xTi4+8-2y-x]O16 ceramics for radioactive caesium immobilization

[CsxBay][(Al3+,Ti3+)2y+xTi4+8-2y-x]O16 (0.4 ≤ x, y ≤ 0.8) ceramics were synthesized to investigate the substitution effects of Ba2+ for Cs+ on the stability of hollandite-ceramic waste forms. It was found that the substitution of Ba2+ for Cs+ in the (Cs,Ba)-hollandite system does not cause substantial variation in the crystallographic phase and microstructure. The normalized release rates of Cs and Ba at 90 °C in deionized water were < 0.005 g m−2 d−1 after 28 days. These results indicate that hollandite ceramics are an ideal host for permanent radioactive caesium disposal.

The effect of Ba doping on Sr site on structural and superconducting properties of Bi2212 phase

In this research, we investigate the effect of Ba substitution on Sr sites in the Bi-2212 system. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), Raman spectroscopy and AC susceptibility measurements give structural and magnetic properties of the prepared samples. The results reveal the following. X-ray diffraction shows that the Bi-2212 phase is dominant and that the secondary Bi-2201 phase decreases as Ba content increases. Ba doping decreases the cell parameter of the samples. SEM reveals a structure of well-connected grains with a shape of plate. Raman spectroscopy shows the modes of vibration that are present in the superconducting material Bi2Sr(2-x)BaxCaCu2O8+δ. AC susceptibility shows that Ba substitution decreases the critical temperature (Tc).

Mineralogy of Deep-Sea Coral Aragonites as a Function of Aragonite Saturation State

In an ocean with rapidly changing chemistry, studies have assessed coral skeletal health under projected ocean acidification (OA) scenarios by characterizing morphological distortions in skeletal architecture and measuring bulk properties, such as net calcification and dissolution. Few studies offer more detailed information on skeletal mineralogy. Since aragonite crystallography will at least partially govern the material properties of coral skeletons, such as solubility and strength, it is important to understand how it is influenced by environmental stressors. Here, we take a mineralogical approach using micro X-ray diffraction (XRD) and whole pattern Rietveld refinement analysis to track crystallographic shifts in deep-sea coral Lophelia pertusa samples collected along a natural seawater aragonite saturation state gradient (Ωsw= 1.15–1.44) in the Gulf of Mexico. Our results reveal statistically significant linear relationships between rising Ωsw and increasing unit cell volume driven by an anisotropic lengthening along the b-axis. These structural changes are similarly observed in synthetic aragonites precipitated under various saturation states, indicating that these changes are inherent to the crystallography of aragonite. Increased crystallographic disorder via widening of the full width at half maximum of the main (111) XRD peaks trend with increased Ba substitutions for Ca, however, trace substitutions by Ba, Sr, and Mg do not trend with crystal lattice parameters in our samples. Instead, we observe a significant trend of increasing calcite content as a function of both decreasing unit cell parameters as well as decreasing Ωsw. This may make calcite incorporation an important factor to consider in coral crystallography, especially under varying aragonite saturation states (ΩAr). Finally, by defining crystallography-based linear relationships between ΩAr of synthetic aragonite analogs and lattice parameters, we predict internal calcifying fluid saturation state (Ωcf = 11.1–17.3 calculated from b-axis lengths; 15.2–25.2 calculated from unit cell volumes) for L. pertusa, which may allow this species to calcify despite the local seawater conditions. This study will ideally pave the way for future studies to utilize quantitative XRD in exploring the impact of physical and chemical stressors on biominerals.

Simulation of radioactive decay by barium substitution for cesium in sodium aluminum-iron phosphate glass

Simulation of 137Cs radioactive decay to 137Ba by an equiatomic substitution of Cs with Ba in a 30 Na2O, 10 Cs2O, 10 Al2O3, 10 Fe2O3, 40 P2O5 (mol%) glass was studied by X-ray diffraction, scanning electron microscopy, Fourier Transform Infrared spectroscopy, Mossbauer spectroscopy, and measurement of hydrolytic durability. Gradual Ba substitution for Cs yielded minor changes in the structural network but did not offer appreciable effect on phase composition and hydrolytic durability of the glasses.

Yellow phosphors Ba2Mg(PO4)2: Eu2+ fit for white light-emitting diodes prepared with sol-gel precursor route

Yellow/orange-emitting Ba2Mg(PO4)2: Eu2+ phosphors with uniform particle size distribution were successfully prepared by Pechini sol-gel method. The emission spectra of Ba2-xMg(PO4)2: xEu2+ phosphor displayed one broad band centered at about 560 nm which can be assigned to the 4f65d1→4f7 transitions of the Eu2+. Along with the increasing of the Eu2+ doping amount the emission peak intensity increased till the Eu2+ concentration ratio is 4 mol%. In Ba2Mg(PO4)2: Eu2+ phosphors, Eu2+ ion occupy two different lattice sites by substitution for Ba2+ ions. with the increase of the doping concentration of Eu2+ ion, the ability for Eu2+ enter into the first site of Ba2Mg(PO4)2 in the lattice is increasing.

Influence of Ba Substitutions on Microstructure and Magnetic Properties of La–Ca–Co System Permanent Ferrite

La0.6Ca0.4−xBaxO⋅n/2(Fe1−yCoy)2O3(x = 0, 0.05, 0.1, 0.15 and 0.2) permanent ferrite materials were prepared by ceramic technique. The topography and the structure were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD), respectively. The magnetic properties were measured using vibrating sample magnetometer (VSM) and digital magnetometer. Single M-phase and flake-like grains were obtained for samples without Ba substitution(x = 0), and the magnetic properties of the pre-sintering La–Ca–Co ferrite were as follows: Br = 440 mT, Hcb = 296 kA/m, Hcj = 426 kA/m, (BH)max = 36.6 kJ/m3 and Hk/Hcj = 0.83. When Ca was substituted by Ba, pre-sintered powder presents single M-phase structure and close three-dimensional size of grains, resulting in an improved rectangle ratio of sintered magnet. The rectangle ratio of sintered magnet reaches a maximum of 0.93 when x = 0.1. By optimizing process parameters, M-type La–Ca–Ba–Co sintered magnet was prepared with Br = 445 mT, Hcb = 337 kA/m, Hcj = 420 kA/m, (BH)max = 38.6 kJ/m3 and Hk/Hcj = 0.95.

Magnetic and Mössbauer investigations of soft Co2Z-type hexa nanoferrites

Co2Z-type hexa nanoferrites of the series Ba3-XSrXCo2Fe24O41 (where x = 0, 0.5, 1.0, 1.5 and 2.0) are synthesized by sol-gel auto combustion method. The effects of Sr2+ substitution for Ba2+ and optimized synthesis conditions are reported using the structural, magnetic and Mössbauer study. The X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) along with the selected area electron diffraction (SAED) clearly indicate the formation of a single-phased Z-type hexagonal nanoferrites with P63/mmc space group. The hysteresis curves obtained by vibrating sample magnetometer (VSM) at room temperature displayed the typical characteristics of magnetically soft materials indicating the decrease in coercivity with the increase in Sr2+ concentration in synthesized hexa nanoferrites, which are validated by the room temperature Mössbauer spectra with least-squares fit sextets of six distinguishable sites (A: 4fIV, B: 4fIV*, C: 12kVI*, D: 4fVI* + 4eIV, E: 12kVI and F: 2dV + 2aVI + 4fVI + 4eVI). Selection of Sr2+ dopant and sol-gel auto combustion soft chemical route are the leading ways to control the coercivity of Co2Z-type hexa nanoferrites.

Ba(1-x)SrxMg3SiN4:Eu narrowband red phosphor

A new narrowband red phosphor, Ba0.8Sr0.2Mg3SiN4:Eu, suitable for use in LED lighting, has been identified as the optimal composition from the series of Ba(1-x)SrxMg3SiN4:Eu including x = 0, 0.2, 0.5, 0.8, and 1. Experimental X-ray diffraction measurements and structures calculated via density functional theory reveal that Ba(1-x)SrxMg3SiN4:Eu stabilizes in a tetragonal crystal structure, changing to the triclinic structure for Ba >0.8. Narrow band Eu2+ emission is observed in the tetragonal phase, but as a function of Ba substitution onto the Sr site, several properties change in concert: the emission maximum shifts to longer wavelengths, room temperature quantum efficiency improves, Eu2+ decay time increases and thermal stability of emission improves. Concomitant with the structure change to triclinic, the narrow Eu2+ emission band becomes broadened, the bandgap increases, and decay time slows to a typical Eu2+ decay of ∼1 μs. Although significantly moisture-sensitive, the strong absorption of Ba0.8Sr0.2Mg3SiN4:Eu at 450 nm, its emission peak at 635 nm and width of 51 nm FWHM provide efficient color rendering in the red, potentially achieving CRI and R9 values in excess of 95, along with good efficacy, in combination with other phosphors. Excitation intensity droop is comparable to other similar Eu-doped nitrides, but while thermally induced quenching is reduced with Ba substitution, it is still significant. The measured photoluminescence decay for Ba0.8Sr0.2Mg3SiN4:Eu of ∼200 ns is faster than of related Eu-doped nitrides, and together with a Q.E. of only ∼40% suggests the presence of competing non-radiative decay routes, thought to be due to thermal ionization of the Eu2+ excited state to the conduction band. Improved Q.E. for SrMg3SiN4:Eu partially substituted with Ba is likely due to the cation disorder this introduces, suppressing nonradiative processes correlated with lattice vibrations and increasing the population of shallow traps that release electrons on the emission lifetime timescale, consistent with the emission decay time lengthening and Q.E. improvement as a function of Ba content.

Influence of Ba substitution, Fe doping and annealing effect on magnetic and optical properties of Sr0.9Ba0.1Ti1−xFexO3 nanoparticles prepared by the hydrothermal method

Sr0.9Ba0.1Ti1−xFexO3 (x = 0, 0.05, 0.10 and 0.15) nanoparticles were synthesized by the hydrothermal method. Influence of Ba substitution, Fe doping and annealing effect on magnetic and optical properties of these samples was studied. X-ray diffraction (XRD) results indicated a cubic perovskite structure with the increase of lattice parameter and crystallite sizes of all samples owing to the substitution with a larger ionic radius of Ba and Fe ions at Sr and Ti sites in the crystal structure, respectively. Ba substitution could result in a pure phase of annealed samples. Magnetization of as-prepared samples measured at room temperature by vibrating sample magnetometer (VSM) revealed a diamagnetic and paramagnetic behavior of undoped and Fe-doped samples, respectively. Interestingly, annealing could significantly affect the magnetic behavior of all samples i.e. undoped sample showed paramagnetic behavior, whereas all Fe-doped samples exhibited ferromagnetic behavior with the enhancement of saturation magnetization (Ms) from 0.28 to 0.78 emu/g owing to the increase of Fe content. Ferromagnetic behavior was suggested to originate from Fe3+−VO−Fe3+ coupling in the crystal structure due to the promotion of oxygen vacancy (VO) as confirmed by the X-ray photoelectron spectroscopy (XPS) results. Moreover, coercivity (Hc) and remanent magnetization (Mr) also increased from 110–442 Oe to 0.01–0.15 emu/g, respectively. The determined optical band gaps of annealed samples determined by ultraviolet–visible (UV–vis) spectroscopy were found to decrease from 3.3907 to 3.3469 eV with increasing Fe content.

Investigation of dielectric and complex impedance spectroscopic studies of Bi1−xBaxFeO3 (0 ≤ x ≤ 0.30) system

Polycrystalline Bi1−xBaxFeO3 (0 ≤ x ≤ 0.30) samples have been prepared by two stage solid state reaction method. The surface texture of the prepared material exhibited a uniform grain distribution with minor empty space suggesting that the density of the pelletized samples is high and grain size is found to decrease with Ba substitution. An important observation is the stabilization of a dielectric anomaly near the magnetic transition temperature in temperature dependent dielectric studies which is ascribed to the presence of magnetoelectric (ME) coupling. This ME coupling effect has been demonstrated by measuring the effect of varying magnetic fields on the dielectric constant. The dielectric constant increased with increasing applied magnetic field giving a coupling coefficient (er(H) − er(0))/er(0) of 1% at H = 5 kOe at room temperature which demonstrate the importance of these material from application point of view. The dielectric constant is high at low frequencies and is found to decrease at moderate frequencies indicating the Maxwell–Wagner contribution to the dielectric response. The increase in Ba content and temperature resulted in an increase in bulk resistance and exhibits a typical negative temperature coefficient of resistance behavior. A temperature dependent and non-Debye type of relaxation process is revealed by impedance spectroscopic studies. The conductivity spectra revealed the presence of hopping mechanism in the electrical transport process and the activation energies lying in the range from 0.45 to 0.70 eV indicate that the conduction of oxygen vacancies through hopping mechanism.

Hole doping effect on structure, transport and magnetic properties of Dy1-xBaxMnO3 (0 ≤x ≤1)

Structural, electrical and magnetic properties of Dy1-xBaxMnO3 compounds synthesized by the standard solid state reaction route are reported in this paper. For x = 0.0 to 0.5, the compounds have orthorhombic structure and for x = 0.8 and 1.0, the structure changed to hexagonal structure corresponding to 2H. Raman spectra of the materials compliment structural phase transition. Phonon lifetimes estimated from the Raman line width were found to be in the order of pico seconds. X-ray photoelectron spectra of Dy1-xBaxMnO3, revealed the presence of Dy, Ba, Mn and O elements with respective binding energies. Mn ions were found to be in the mixed valent states of Mn (III) and Mn (IV) and their ratio decreased with increasing Ba concentration. Temperature behavior of electrical resistivity of all the compounds showed semiconducting behavior that persisted in the entire temperature range with small polaron hopping conduction mechanism. As Ba content increased, activation energies for hopping of polarons decreased in the orthorhombic phase and increased in the hexagonal phase. Magnetic studies as a function of temperature indicated that ordering temperatures of rare earth (Dy) moments are suppressed with Ba substitution. Random occupation of magnetic Dy3+, Mn3+ and Mn4+ ions in Dy1-xBaxMnO3 system resulted in complex magnetic structures. The reduction in the experimental effective magnetic moments determined from the Curie-Weiss fit parameters followed the magnetic dilution. Isothermal magnetization curves confirmed the presence of multiple interactions between the magnetic ions.

Behavior of lanthanum containing barium stannate nanoparticles synthesized by cetyltriammonium bromide assisted wet chemistry route

In present study, we report dielectric, ferroelectric and pyroelectric behavior of pristine and La3+ containing barium stannate nanoparticles synthesized via wet chemical route involving cetyltriammonium bromide assisted thermal decomposition of binary precursors. The X-ray diffraction patterns of pristine and La3+ (2, 4 and 6 at%) doped BaSnO3 nanoparticles showed the formation of cubic perovskite phase. On substitution of Ba2+ lattice sites by La3+ at the La content of 6 at%, the sample exhibited fourfold increase in conductivity in comparison to pristine BaSnO3. Polarization hysteresis (P-E) curves of La containing barium stannate nanoparticles showed anti-ferroelectric behavior. The pyroelectric coefficient of pristine and La (2, 4 and 6 at%) containing BaSnO3 nanoparticles at 473 K were found to be 7.8, 11.6, 14.1 and 17.2 μCm−2K−1, respectively. Further, the responsivity and detectivity values were higher in comparison to the materials, such as AlN, GaN, CdS and ZnO.

The analysis of mechanical properties of non autoclaved aerated concrete with the substitution of fly ash and bottom ash

Based on PP. No.85 of 1999 on the management of hazardous and toxic (B3), fly ash and bottom ash wastes are categorized into B3 waste because there are heavy metal oxide contents that can pollute the environment. One form of environmental rescue that can be applied is to utilize waste fly ash and bottom ash in the manufacture of concrete. In this research, fly ash and bottom ash waste are used as substitution of cement and fine aggregate to make lightweight concrete. The purpose of this research is to know the mechanical properties of non-autoclaved aerated lightweight concrete (NAAC) with FA and BA substitution to cement and fine aggregate which is expected to improve the quality of concrete. The NAAC lightweight concrete in this study is divided into 4 categories: normal NAAC lightweight concrete, NAAC lightweight NAAC substituted concrete with FA, NAAC lightweight concrete substituted with BA, and NAAC combined light weight from FA and BA with variations of 10%, 20% And 30%. The test specimen used in cylindrical shape, which was tested at the age of 28 days, amounted to 90 pieces and consisted of 10 variations. Each variation amounted to 9 samples. Based on the test results with FA and BA substitutions of 10%, 20%, and 30%, the highest compressive strength was achieved in samples with FA 30% of 12.687 MPa, maximum tensile strength achieved in samples with FA 30% of 1,540 MPa, The highest absorption was achieved in normal NAAC of 5.66%. Based on the weight of the contents of all samples, samples can be categorized in lightweight concrete, since the weight of the contents is less than 1900 kg / m3.

Optimization of fly ash and bottom ash substitution against paving block manufacture according to SNI 03-0691-1996

The waste of coal burning has a very negative impact on the environment if the waste is not managed as well as possible. The remaining waste of coal combustion consists of fly ash and bottom ash. FA and BA can be developed into substitution materials in the process of making paving blocks. The purpose of this study was to determine the quality of paving block in accordance with SK SNI 03-0691-1996 with optimization in the use of FA and BA. This study uses a 351 paving block sample size of 20x10x6 cm. Paving blocks are divided by 4 categories, namely normal paving block, paving block with FA substitution, BA substitution and combination of FA-BA with each variation 0%, 25%, 50%, 75% and 100%. Each variation amounted to 27 samples. Paving block quality measurement is done through 4 tests: absorption, compressive strength, sodium sulphate resistance and Los Angeles tests. The result of the test shows the absorption of normal paving block is 3,229%, paving block with 25% FA is 3,889%, paving block with 50% BA is 5,560% and paving block with 25% FA-BA combination is 5,794%. Compressive strength in normal paving block is 25,50 MPa, paving block with 25% FA is 25,28 MPa, paving block with 25% BA is equal to 27,61 MPa and paving block with 25% FA-BA is 26, 00 MPa. In testing of sodium sulfate resistance, almost all test specimens are eligible except for paving block with 50% FA and 75% FA. In the test of wear resistance, no specimen is eligible according to SK SNI 03-0691-1996. The comparison of the strength of the test specimen can be seen in substitution with 25% BA which reaches maximum strength.

Microwave dielectric properties of barium substituted screen printed CaBi2Nb2O9 ceramic thick films

In the present study, Aurivillius-structured Ba2+ substituted CaBi2Nb2O9 (CBNO) ceramic powder was synthesized by co-precipitation method. The CBNO thick films were delineated by screen printing method on alumina substrates using co-precipitated ceramic powder. The overlay method was adopted to measure the microwave dielectric properties of prepared thick films. Single phase layered perovskite structure of the prepared thick films was confirmed by X-ray Diffraction. The effects of Ba2+ substitution on the surface morphology, bonding, and microwave dielectric properties of thick films were systematically presented. The maximum value of microwave dielectric constant for the CBNO thick films at 11.8GHz is 15.6 for Ba2+=0.8 substitution. The shift in the stretching vibration modes of the Nb-O bond of NbO6 octahedron in the Raman spectra with a substitution of Ba2+ in CBNO was observed. The substitution of Ba2+ on A-site of CBNO improves the microwave dielectric properties of prepared thick films. This work may provide a new approach to enhance the microwave dielectric performance of Aurivillius-structured ceramic thick films.

Cetyltriammonium Bromide Assisted Synthesis of Lanthanum Containing Barium Stannate Nanoparticles for Application in Dye Sensitized Solar Cells

In present work, correlation of structural and optical behavior of pristine and lanthanum containing barium stannate nanoparticles (synthesized via cetyltriammonium bromide (CTAB) assisted facile wet chemical route), and its effect on photovoltaic properties of dye‐sensitized solar cell are reported. Thermo‐gravimetric analysis of the dried compound presumably BaSn(OH)6, leads to the formation of BaSnO3 nanoparticles through three endothermic decomposition processes, via liberation of one mole of water in each step, together with removal of remaining CTAB in initial cycle. The X‐ray diffraction patterns reveal that substitution of Ba2+ lattice sites by La3+ (upto ≈6 at.%), the lattice retains its cubic Pm3m symmetry, however, unit cell contracts. The dye sensitized solar cells are fabricated using pristine and La‐ containing BaSnO3 as photo anode; platinum coated FTO as counter electrode, N719 dye as sensitizer and I−/I3− as electrolyte. These show the highest power conversion efficiency (≈9.2%) at the La content of 6 at.% which is about threefold increase in efficiency in comparison to pristine BaSnO3. The electron transport properties of these DSSC devices are investigated by electro chemical impedance spectroscopy.

The impact of Ba substitution on high-temperature transport in lanthanum-strontium ferrite

Effect of barium content on structural, thermal, and transport properties of oxides La0.49Sr0.5–x Ba x FeO3–δ (х = 0, 0.25, 0.50) was studied with the emphasis on their potential use for electrodes and oxygen transport membranes. Barium substitution for strontium was found to enhance symmetry of crystalline lattice, facilitate the oxygen release on heating, and favor the increasing thermal expansion of La0.49Sr0.5–x Ba x FeO3–δ . Analysis of electrical conductivity depending on the partial oxygen pressure allowed to separate the contributions of oxygen ions, electrons, and holes in high-temperature electrical transport in order to trace barium effect on conductivity components. Electron conductivity of n-type and its activation energy does not reveal sensitivity to barium concentration in oxides. Oxygen ion conductivity is shown to decrease with increasing barium content in La0.49Sr0.5–x Ba x FeO3–δ while respective activation energy increases from 0.70 to 0.79 eV. About four times decrease of p-type electron conductivity at invariable activation energy was detected as a result of the substitution degree increase from x = 0 to x = 0.5. Possible mechanisms of barium influence on properties of oxides are discussed.

Influences of substituting Na+ ions in Eu2+, Mn2+ doped Ba9Y2Si6O24 phosphors

Near-ultraviolet (NUV)-excitable phosphors composed of Ba8.9-(1/2)pNapEu0.1Y2Si6O24 (p=0–0.8) and Ba8.7-qNa0.4Eu0.1MnqY2Si6O24 (q=0–0.4) were prepared via a solid-state reaction in a reducing atmosphere. The X-ray diffraction patterns of the obtained phosphors were examined to index the peak positions. After Na+ substitution for Ba2+ in the Ba8.9Eu0.1Y2Si6O24 host lattice, the clear shift from green to yellow emission was observed. The Gaussian components of Ba8.9-(1/2)pNapEu0.1Y2Si6O24 (p=0, 0.4, and 0.8) phosphors were exploited by using the three different Eu2+ ion sites in the host lattice. The dependence of the luminescent intensity of the Mn2+ co-doped (q=0–0.4) host lattices on the fixed Na+ and Eu2+ contents was also investigated. Co-doping Na+ with Mn2+ and Eu2+ emitters in the host structure enabled efficient energy transfer from Eu2+ to Mn2+. The mechanism underlying this energy transfer was also discussed. The Commission Internationale de I’Eclairage (CIE) coordinates near the yellow and red regions of the obtained phosphors were observed. Each of Ba8.9Eu0.1Y2Si6O24, Ba8.7Na0.4Eu0.1Y2Si6O24, and Ba8.6Na0.4Eu0.1Mn0.1Y2Si6O24 phosphors with a 405nm LED chip was fabricated. The color rendering index (CRI, Ra) at correlated color temperature (CCT) with the CIE coordinates was exhibited for the LEDs. The thermal quenching and activation energy for the Ba8.7Na0.4Eu0.1Y2Si6O24 and Ba8.6Na0.4Eu0.1Mn0.1Y2Si6O24 phosphors were measured.

Ba2Mg(BO3)2:Bi3+ - A new phosphor with ultraviolet light emission

Ultraviolet light emission was observed in a new Ba2Mg(BO3)2:Bi3+ phosphor. Bi3+ substitution for Ba2+ in the lattice was supplemented with K+ to maintain the charge neutrality. The samples of the formula Ba2-2xBixKxMg(BO3)2 [x = 0, 0.001, 0.01, 0.02, and 0.05] synthesized by solid state reaction were characterized using powder X-ray diffraction for their phase formation. Raman and diffuse reflectance UV-Vis spectroscopic techniques were used to obtain information on the vibrational modes and optical properties, respectively. The room temperature photoluminescence measurements revealed an ultraviolet emission at 370 nm when excited using 304 nm wavelength and the Stokes shift is 5868 cm−1.

Effects of alkaline-earth dopants on structural, optical and magnetic properties of Bi2Fe4O9 powders

The pure Bi2Fe4O9 and Bi2 (1−x) A2xFe4O9 (A = Ca, Ba, x = 0.03) powders are synthesized via a modified solid-state reaction method to study the effects of alkaline-earth metal ions doping on crystal structural, optical and magnetic properties. Both X-ray diffraction and Raman spectroscopy data reveal that all the powders are Mullite-type Bi2Fe4O9 orthorhombic single phase without any impurities. Much greater structural distortion in Bi1.94Ba0.06Fe4O9 than that of Bi1.94Ca0.06Fe4O9 is observed. The chemical compositions of Ba2+ and Ca2+ doped powders have been investigated with energy dispersive X-ray spectroscopy (EDS). X-ray photoelectron spectroscopy results indicate that oxygen vacancies could be found in all doped powders. The ratio of Fe2+ in the total Fe ions is almost unchanged by Ca doping and increases a little with Ba substitution. Compared with that of pure Bi2Fe4O9, the band gap values decrease slightly in Bi1.94Ca0.06Fe4O9 but drop dramatically in Bi1.94Ba0.06Fe4O9. A clear and obvious ferromagnetic behavior is found in Bi1.94Ba0.06Fe4O9 at 10 K. However, Bi1.94Ca0.06Fe4O9 shows a weak ferromagnetism with enhanced magnetization and Bi2Fe4O9 exhibits antiferromagnetism with a linear M–H relationship. The varied bandgap and magnetization resulting from the alkaline-earth metal ionic species are discussed in terms of structural distortion due to the ionic radius size effect.