Influence of Strontium Doping on the Electrical Resistivity and Microhardness of Gel Grown Lanthanum Tartrate Crystals

This study investigates the impact of strontium doping on the electrical resistivity and microhardness of gel-grown lanthanum tartrate crystals with stoichiometric compositions of (La)₁₋ₓ(Sr)ₓC₄H₄O6.nH₂O, where x = 0, 0.10, and 0.15. Detailed resistivity measurements reveal a clear trend of decreasing resistivity with increasing strontium concentration. The experimental data conform well to Mott’s variable range hopping (VRH) model, indicating that strontium incorporation into the lanthanum tartrate matrix reduces the gap parameters from 190.95 meV to 175.505 meV. This reduction suggests enhanced electrical conductivity, attributed to an increase in carrier density and modified hopping parameters. Specifically, calculations based on the VRH model indicate changes in carrier density, hopping energy, and hopping distances for the polycrystalline spherulitic crystals across all compositions. Additionally, the microhardness of these crystals was evaluated using the Vickers hardness test under varying loads from 0.049 N to 2.9 N. Analysis using Hays and Kendall’s law enabled the determination of load-independent Vickers microhardness values for each composition. The results demonstrate that strontium doping not only affects the electrical properties but also enhances the mechanical robustness of lanthanum tartrate crystals, making them more suitable for practical applications requiring both electrical conductivity and mechanical strength. This comprehensive study underscores the potential of strontium-doped lanthanum tartrate crystals in advanced material applications.