Unusual emission generated from Ca2Mg0.5AlSi1.5O7:Eu2+ and its potential for UV-LEDs and non-contact optical thermometry

Highlights: • The Ca₂Mg_0.5AlSi_1.5O₇:Eu²⁺ ions were successfully obtained via the sol gel method. • The emission of Eu²⁺ ions covers whole visible spectral range (390–725 nm). • The samples indicated intense green emission with CIE of (0.28, 0.44). • The quantum efficiency of the dopant ions emission was measured to be 40%. • Highest S_r value of studied material reaches 1.62%K⁻¹ at 350 K. -- Abstract: Ca₂Mg_0.5AlSi_1.5O₇ samples doped with europium ions were successfully obtained via a sol gel method. The reduction of Eu³⁺ to Eu²⁺ ions was provided by the vacuum atmosphere. The samples exhibited regular and intense green emission, and also abnormal violet-blue emission. Both of them were related with the 5d → 4f transition of Eu²⁺ located in the calcium sites. However, the violet-blue emission of Eu²⁺ is related with the presence of oxygen defects. The luminescence properties, decay times, and thermal stability were studied in detail and showed that the samples indicated the intense green emission with CIE of (0.27, 0.38) and a quantum efficiency of 40%. It was demonstrated that the intensity ratio of green to violet-blue emission bands can be used in the non-contact optical thermometry field because of high relative sensitivity 1.62%K⁻¹ at 350 K. Based on excitation, the emission and thermal quenching measurements of the size of the energy band gap (E_g = 7.42 eV) and the location of the 4f and 5d energy levels of Ln²⁺ and Ln³⁺ ions in Ca₂Mg_0.5AlSi_1.5O₇ were determined.