Conversion of blue emitting thermally stable Ca3Bi(PO4)3 host as a color tunable phosphor via energy transfer for luminescent devices

Eulytite type crystalline structure of Eu3+ activated Ca3Bi(PO4)3 phosphors have been synthesized via solid-state reaction method in an ambient atmosphere. The diffraction pattern of the synthesized phosphor confirmed the formation of pure and single-phase crystalline with a cubic structure of Ca3Bi(PO4)3 microparticles. The SEM image of Ca3Bi(PO4)3 illustrates the growth of heterogeneous microstructures with some agglomeration. The Ca3Bi(PO4)3 host shows the broad emission peak at 434 nm (blue region) under the excitation wavelength of 326 nm ascribing to 3P1→1S0 electronic transition of Bi3+ ions. The Eu3+ activated Ca3Bi(PO4)3 phosphors exhibited intense red emission band centered at λem = 612 nm (5D0 →7F2) at excitation wavelengths of 393 & 465 nm and perceived that the optimized Eu3+ ion concentration is 8.0 mol%. The host blue emission intensity diminished with increasing Eu3+ concentration, whereas the intensity enhanced for the characteristic peaks of Eu3+ ions located in 550–725 nm range under the host excitation wavelength (λex = 326 nm). This suggests that part of host emission energy was transferred to the activator when the host was doped with Eu3+ activator ions. The CIE color coordinates for the Ca3Bi(PO4)3 host lie in the blue region, which has been modulated towards the red region with increasing Eu3+ ions concentration. However, the CIE coordinate values for Eu3+ doped Ca3Bi(PO4)3 phosphor fall in the red region at λex = 393 & 465 nm with high color purity. The average decay time of the optimized phosphor was in the range of milliseconds. The PL intensity persists up to 75.45% at 200 °C that of at ambient temperature, assuring the excellent thermal stability of phosphor. The combination of the above revealed results recommends that Ca3Bi(PO4)3: Eu3+ phosphor can be a probable contestant in near-UV/blue excited luminescent devices.