Tweaking the structure and symmetry of Y2B2O7:Eu3+ by B-site engineering for efficient and thermally stable phosphor: Y2Zr2O7 versus Y2Ge2O7

There is an urgent need for synthesizing red emitting phosphor with high photoluminescence quantum yield (PLQY) and good thermal stability for high performing phosphor converted light emitting diodes (pc-LEDs) which are in demand to mitigate carbon emission. Here we have achieved the same through symmetry alteration and structural modification strategy which leads to high PLQY and improved thermal stability. In this work we have synthesized highly symmetric cubic fluorite Y2Zr2O7:Eu3+pyrochlore and replacing the B-site Zr4+by Ge4+ to lower the symmetry and induce structural change to tetragonal Y2Ge2O7:Eu3+ by organic solvent free solid state reactions. Among the three composition Y2Ge2O7: Eu is exhibiting higher emission intensity, higher asymmetry ratio and enhanced PLQY (32.3 %) by virtue of lower symmetry of tetragonal phase. On the other hand, higher thermal stability was achieved for Y2Zr2O7: Eu (97 % at 450 K) endowed by higher structural integrity and stability of pyrochlore phase.