Synthesis and Characterization of Potassium Titanyl Phosphate (KTiOPO4) Nanocrystals: The Impact of Hydrothermal and Co-Precipitation Methods with Oxalic Acid Capping Agent

Potassium titanyl phosphate (KTiOPO4), commonly known as KTP, is renowned for its applications in quantum and optical technologies. This study focused on the synthesis of KTP nanocrystals using hydrothermal and co-precipitation methods, employing oxalic acid as a capping agent. X-ray powder diffraction (XRD) analysis confirmed the successful synthesis of orthorhombic KTP crystals. Fourier Transform Infrared (FT-IR) spectroscopy further validated the bond structures within KTP, with characteristic bands corresponding to its crystal structure observed consistently across all spectra. Quantitative analysis revealed that the hydrothermal method produced KTP nanoparticles with an average grain size of approximately 35 nm, whereas the co-precipitation method yielded smaller nanoparticles with an average grain size of 22 nm. Notably, the introduction of oxalic acid as a capping agent in the hydrothermal method reduced the grain size by 15% to about 30 nm, while in the co-precipitation method, it unexpectedly increased the grain size by 20%, resulting in nanoparticles with an average grain size of 26 nm. Additionally, the strain within the crystal lattice was found to be higher in co-precipitated samples (approximately 0.8%) compared to those synthesized via the hydrothermal method (approximately 0.5%). These findings underscore the significant influence of synthesis methods and capping agents on the size, morphology, and structural integrity of KTP nanoparticles. The hydrothermal approach demonstrated efficacy in producing larger nanoparticles, whereas the presence of oxalic acid as a coating agent played a pivotal role in controlling grain size and enhancing structural stability. Such insights are crucial for optimizing the synthesis of KTP nanoparticles tailored for various applications in optical devices, photonics, and quantum technologies.