Energy transfer from Mn4+ to Mn5+ and near infrared emission with wide excitation band in Ca14Zn6Ga10O35:Mn phosphors

Ca14Zn6Ga10-xO35:xMn(CZG:xMn) phosphors were synthesized by high temperature solid state reaction. High doping concentration as 30 mol% for Mn ions can be realized in the compounds due to the existence of the multiple valance of Mn ions. Both red emission from Mn4+ and near infrared (NIR) emission from Mn5+ were observed from CZG:xMn phosphors. The energy transfer from Mn4+ ions to Mn5+ ions was detected, which makes it possible for CZG:xMn phosphors to emit 1152 nm light under the excitation of the whole visible light region, especially under the commercial blue chips (450 nm). This means the CZG: xMn phosphors can be used in the manufacture of NIR sources with small size, simple structure and low cost. Because CZG:xMn can be excited by 600 ~ 700 nm and emits 1152 nm, the phosphors show the application in the real-time biochemical detection because of the excellent penetration capacity of biological tissue for 600 ~ 700 nm and 1152 nm light. With the aid of low-temperature PL spectra, it was found that two zero phonon lines and multiple vibration bands are responsible for the five compact emission band from 650 ~ 750 nm of Mn4+ ions. The results are helpful to comprehend the mechanism of the emission of Mn ions in CZG:xMn and promote the phosphors application.