Synthesis and luminescence properties of a broad-band red phosphor Ca3Si2O7:Eu2+ for warm white light-emitting diodes

► Pure Ca3Si2O7:Eu2+ phosphor was successfully synthesized by adding H3BO3 . ► Effects of H3BO3 on phase formation and emission intensity were presented. ► Luminescence properties in conjunction with Ca3Si2O7 structure were studied. ► Energy transfer mechanism of Eu2+ and its critical distance were proposed.