Mn4+/Tm3+ co-doped Ca14Zn6Al10O35 near infrared phosphor is prepared with a sol-gel method and intense 1.85 mu m emission of Tm3+ sensitized by Mn4+ is observed for the first time. The intense and broad excitation band of Mn4+ (250-550 nm) and efficient Mn4+ -> Tm3+ energy transfer make the 1.85 mu m emission very convenient to be obtained by pumping with light in a wide-wavelength region, especially with commercial GaN LEDs. The mechanisms for the Mn4+ -> Tm3+ and Tm3+-Tm3+ interaction have been discussed based on the Mn4+ and Tm3+ concentration dependent steady-state and transient spectral properties. It is found that both the Mn4+ -> Tm3+ sensitization and the Tm3+-Tm3+ inter-action are helpful to the improvement of the near infrared luminescence, resulting in the 1.85 mu m emission for the Mn4+/Tm3+ co-doped phosphor 24 times of enhancement under excitation of 455 nm light as compared with that for the Mn4+ absent sample. (c) 2015 Published by Elsevier B.V.