JEOS RP ISSN03 | Page 21

14

J. Eur. Opt. Society-Rapid Publ. 22, 2( 2026)

Figure 1. Characterization of Bi 1-x Mn x O 3 thin films.( a) Full-range XRD patterns show a dominant preferred orientation.( b) A close-up of the primary peak region( 27 °– 30 °) shows a constant shift in the 2h position, indicating a change in the out-of-plane lattice parameter due to the incorporation of varying amounts of Mn.

formation of oxygen vacancies to maintain charge balance, a common phenomenon in such oxide systems. The average crystallite size and lattice strain of the synthesized Bi 2-x Mn x O 3 powders were determined using the Williamson-Hall( W-H) analysis. This method is based on the principle that the broadening of X-ray diffraction( XRD) peaks is caused by two main factors:( 1) the finite size of the crystallites( size broadening), and( 2) lattice distortions due to imperfections such as dislocations, point defects, or dopant-induced strain( strain broadening). The total broadening( b total) isexpressedasalinearcombination:

b total ¼ b size þ b strain; ð1Þ

where b size is related to the crystallite size( D) by the Scherrer equation, and b strain is proportional to the strain( e). This relationship is formulated in the following equation, known as the uniform deformation model( UDM) of the W-H plot:

b hkl cos h ¼ðKk = DÞ þ4e sin h:

Here, b hkl is the full width at half maximum( FWHM in radians) of a specific( hkl) reflection, h is the Bragg angle, K is the Scherrer constant( a shape factor, ~ 0.9), k is the X-ray wavelength, D is the volume-weighted average crystallite size, and e is the effective microstrain.

The influence of manganese doping on the structural parameters of Bi 2-x Mn x O 3, as determined from X-ray diffraction line broadening analysis, is summarized in Table 1. A remarkable reduction in crystallite size by an order of magnitude is observed with the introduction of a small amount of Mn( x = 0.025), decreasing from

~ 1633 nm for the pristine sample( x = 0) to ~ 88 nm. This

suggests that Mn doping effectively inhibits crystallite growth. As the doping level increases further( x = 0.05 to x = 0.1), the crystallite size does not follow a simple trend, fluctuating between 247 nm and 617 nm, which may indicate complex changes in the nucleation and growth dynamics. Concurrently, the microstrain within the crystals shows a general increasing trend with higher Mn content. The lowest strain( 0.00315) is found for x = 0.025, while the highest( 0.0093) is for x = 0.1. This inverse correlation between crystallite size and strain is a common phenomenon in doped materials, where lattice distortions

ð2Þ

Table 1. The calculated crystalline size and strain of Bi 2- xMn x O 3.

induced by the dopant ions lead to increased internal strain, particularly at higher concentrations.

The FESEM images in Figure 2 exhibit how the surface of Bi 2-x Mn x O 3 thin films changes with different amounts of manganese added. When the Mn concentration is low( image a), the surface looks smooth and dense, suggesting that the grains have grown uniformly with very few defects. This type of surface typically results in fewer grain boundaries and greater crystal clarity, which can enhance the electrical and magnetic properties of the material. As the Mn content causing the observed porosity, and instead link the morphological changes to the inhibitory effect of Mn doping on crystal growth and its promotion of agglomerate formation. On the hand of the surface porosity and the grain size, the substitution of smaller Mn ions for Bi ions induces lattice strain, causing the increase in grain size and surface porosity seen at the highest Mn doping level. This strain disrupts crystal development, encouraging grain merging to form larger grains, which lowers the strain energy. The strain also results in internal voids and flaws that manifest as elevated porosity and surface roughness. This explains the morphological changes detected by FE-SEM. These changes in surface texture can affect how well the material conducts electricity and responds magnetically. Overall, the SEM images show how adding Mn changes the film’ s structure, which is important when designing these materials for electronics or spintronics applications.

The connection between a material’ s absorbance and wavelength provides insights into its electronic structure, with spectral peaks indicating electronic transitions that