Effect of lanthanum doping on the structure and optical properties of nanocrystalline vanadium pentoxide films prepared by sol–gel method

Abstract

The structural and optical properties of lanthanum oxide doped nanocrystalline vanadium pentoxide films with the chemical composition xLa2O3-(1-x)V2O5.nH2O (where x = 0.25, 0.50 and 1.0 mol%) prepared by sol–gel method were studied. The XRD analysis also revealed that the (002) line is noticeable in the pure film and gets sharper by the addition of Lanthanum, which indicates a layer of intercalation between the vanadium layers. The average crystallite size decreased with increasing Lanthanum content from 4.45 nm to 3.57 nm. By using double-beam UV–VIS spectrophotometers, the optical properties were studied by measuring the absorption, reflectance and transmittance of the prepared films. Some optical parameters like absorption coefficient α, dispersion energy parameters, refractive index n, optical band gap Eop for various transition mechanisms, real parts and imaginary part of the dielectric constants and effective mass were calculated. The absorption coefficient slightly increases with increasing La content, which can be attributed to the increasing of lattice distortion as a result of crystallite size increasing as indicated in the XRD. The transition mechanism was found to be indirect allowed type with optical band gap Eop increasing relative to the La content. By assuming hydrogen like model, the carrier’s contents N were deduced. The absorption spectrum behavior in visible and UV region suggests a promising solution for solar cells and optical-electronic applications.

The Impact of TiO 2 - Doped V 2 O 5 Films on the Structural, Linear and Nonlinear Optical Behavior for Optoelectronic Applications

“…The reason for this drop is that bigger Titanium ions Ti 4+ (ionic radius ~ 68 pm) have replaced part of the vanadium ions V 5+ (ionic radius ~ 54 pm) in the layered structure, causing strain and stress due to compression [27]. The wide 2θ = 6.5 ~ 6.7 peak widths suggest a fine or noncrystalline structure, and all of the peaks show an intense c-axis orientation, which is consistent with previously reported studies and earlier research [5,28]. The identified peaks were discovered to be valid in accordance with the JCPDS card code number 00-040-1296, which represents vanadium pentoxide xerogel with an orthorhombic crystal structure [29].…”

“…The wide 2θ = 6.5 ~ 6.7 peak widths suggest a fine or noncrystalline structure, and all of the peaks show an intense c-axis orientation, which is consistent with previously reported studies and earlier research [5,28]. The identified peaks were discovered to be valid in accordance with the JCPDS card code number 00-040-1296, which represents vanadium pentoxide xerogel with an orthorhombic crystal structure [29]. Debye-Scherer's equation 𝑫 = 𝒌𝝀 𝜷 𝒄𝒐𝒔 𝜽 was accustomed get the average crystallite size (D) [30].…”

“…Additionally, the reflectance drops with the addition of TiO2 % between 520 and 1000 nm. There is overlapping behavior in the infrared spectrum between 900 and 1000 nm, which is associated with the nanocrystallinity of V2O5 [29]. Employing the absorption information the coefficient of absorption (α) for the produced samples was calculated following the equation that follows [31,32].…”

“…With its orthorhombic layered structure, crystalline V2O5 exhibits several favorable characteristics, including a 𝐸 𝑔 𝐷𝑖𝑟𝑒𝑐𝑡 , exceptional individual energy, and thermal permanence suitable for multidisciplinary purposes [4]. Because of these features, scientists have been able to investigate the potential uses of V2O5, including optoelectronic devices [5], and catalysts [6]. Different varieties of solid-state light indicators, including p-n junction class [7], metal-semiconductormetal type [8], and photoconductors, became employed for optoelectronic applications.…”

“…The most popular technique for creating doped optical materials is thes ol-gel process, which entails turning a colloidal solution (called "Sol") into a "gel" that has combined liquid and solid phases. Compared to the majority of chemical solid-state processes, this technology has a number of advantages, such as lower in-process temperatures, fewer contaminants, and better uniformity with homogeneous nanometer-sized particle dispersion [5,17,18]. Sol-gel technologies make it easy to create films employing a variety of methods, which makes them perfect for studying optical characteristics.…”