Deep reddish-orange emitting Sr3Gd(PO4)3: Sm3+ phosphors via modified citrate-gel combustion method

•SGPSmx phosphors are prepared by modified citrate-gel combustion method.•Crystallized into BCC phase with average crystallite size of 55–58 nm.•The d-d interaction energy transfer among Sm3+ ions cause luminescence quenching.•SGPSm1.0 phosphor emits deep reddish-orange emission at 403 nm excitation.•SGPSm1.0 phosphor has highest potentiality to replace commercial red phosphors.