<p>The present research work investigates the synthesis of Dy³⁺-doped, Tb³⁺-doped, and Dy³⁺/Tb³⁺-co-doped Sr₂ZnSi₂O₇ (SZSi) phosphors using a high-temperature solid-state technique. X-ray diffraction (XRD) analysis showed that the crystal structure of the synthesized SZSi samples matched the Joint Committee on Powder Diffraction Standards (JCPDS) card no. 00-039-0235. Using diffuse reflectance spectroscopy (DRS), the bandgap of co-doped SZSi:Dy³⁺/Tb³⁺ phosphor was determined to be 3.09&#xa0;eV. Emission spectra from photoluminescence (PL) spectroscopy showed that SZSi:Dy³⁺, SZSi:Tb³⁺, and SZSi:Dy³⁺/Tb³⁺ phosphors were efficiently excited by near-ultraviolet light. As the concentration of Tb³⁺ ions increased, their PL intensity also increased, causing the PL emission intensity of Dy³⁺ ions to drop, representing the energy transfer from Dy³⁺ to Tb³⁺ ions in the host lattice. The correlated colour temperature (CCT) value for the SZSi:Dy³⁺/Tb³⁺ (<i>x</i> = 1.5, <i>y </i>= 2&#xa0;mol.%) phosphor was 3091&#xa0;K, whereas the CIE colour coordinates were (0.31793, 0.30735), representing warm white light luminescence. Additionally, with activation energy of 0.236&#xa0;eV, the synthesized phosphor demonstrated outstanding thermal stability, maintaining 88% of its emission intensity at 150°C. These results demonstrate the potential of the synthesized phosphors as solid-state warm white-light-emitting diode (LED) lighting sources.</p>