Supplement Number 1

Calculation and experimental methods, dielectric constant and loss along c-axis (Table S1) and a-axis (Table S2) respectively, conductance activation energy (Table S3), CIE coordinates, color purity, dominant wavelength and CCT at varied temperature (Table S4) and at varied pressure (Table S5) respectively, comparison of XRD pattern refinement results at ambient condition (Fig. S1), temperature-dependence of XRD patterns and unit cell parameters (Fig. S2), temperature-dependence of Raman spectra (Fig. S3), pressure-dependence of IED/IMD (Fig. S4), high-pressure XRD refinement (Fig. S5), pressure-dependence of XRD patterns (Fig. S6) and pressure-dependence of Raman spectra of (La1-xSmx)2Ti2O7 crystals (Fig. S7).