Sol-gel auto combustion synthesis of metal oxide materials for energy harvesting and photocatalytic applications.

Abstract

This study explored the properties of different types of oxide materials synthesized using a sol-gel auto-combustion technique. The study investigated n-type materials such as Sr1-xLaxTiO3 (SLTO) and SrTi1-xNbxO3 (STNO), and p-type materials such as Ca3-xAgxCo4O9 (CACO). The materials were characterized for their structural, optical, photocatalytic, and thermoelectric properties using various techniques such as XRD, SEM, SEM-EDS, UV-Vis, etc.

First, the study investigated the effect of La3+ substitution in Sr2+ on the structural and photocatalytic properties of SLTO powder. The results showed an increase in lattice parameters, unit cell density, and specific surface area with higher La doping content, while the crystallite and particle size decreased. The photocatalytic activity of SLTO increased with increasing La content and reached a maximum at x = 0.07, with the proposed mechanism highlighting the role of oxygen vacancies in the structure. The study also found that SLTO bulk ceramics produced using spark plasma sintering (SPS), exhibited promising thermoelectric properties, with the highest values of electrical conductivity, negative Seebeck coefficient, and dimensionless figure of merit (ZT) at x = 0.01 at 800 K.

Second, the study investigated the effect of Nb doping on STNO powder properties. The results showed that Nb doping increased the number of lattice parameters and unit cell density, and decreased the particle size. The photocatalytic activity of STNO increased with increasing Nb content, peaking at x = 0.05. The study suggests that Nb doping can enhance the photocatalytic performance of STNO.

Lastly, the study successfully synthesized the high-density CACO bulk by using sol-gel auto combustion, followed by SPS technique. The thermoelectric properties of CACO bulk samples were investigated. The addition of Ag resulted in porosity and non-uniform chemical distributions. All samples exhibited a positive Seebeck coefficient and decreasing thermal conductivity with increasing temperature. The maximum ZT value of 0.18 at 950 K for x = 0 suggests the potential of CACO-based materials as thermoelectric materials.

Overall, the study findings suggest that the synthesized oxide materials by sol-gel auto combustion technique, have promising potential for use in energy harvesting and conversion and could be useful in various photocatalytic applications.

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