High pyroelectric performance and good thermal stability of pyroelectric materials are desirable for the application of infrared thermal detectors. In this work, enhanced pyroelectric properties were achieved in a new ternary (1-x)(0.98(Bi0.5Na0.5)(Ti0.995Mn0.005)O-3-0.02BiAlO(3))-xNaNbO(3) (BNT-BA-xNN) lead-free ceramics. The effect of NN addition on the microstructure, phase transition, ferroelectric, and pyroelectric properties of BNT-BA-xNN ceramics were investigated. It was found that the average grain size decreased as x increased to 0.03, whereas increased with further NN addition. The pyroelectric coefficient p at room temperature (RT) was significantly increased from 3.87x10(-8)Ccm(-2)K(-1) at x=0 to 8.45x10(-8)Ccm(-2)K(-1) at x=0.03. The figures of merit (FOMs), F-i, F-v and F-d, were also enhanced with addition of NN. Because of high p (7.48x10(-8)Ccm(-2)K(-1)) as well as relatively low dielectric permittivity (similar to 370) and low dielectric loss (similar to 0.011), the optimal FOMs at RT were obtained at x=0.02 with F-i=2.66x10(-10)m/V, F-v=8.07x10(-2)m(2)/C, and F-d=4.22x10(-5)Pa(-1/2), which are superior to other reported lead-free ceramics. Furthermore, the compositions with x0.03 exhibited excellent temperature stability in a wide temperature range from 20 to 80 degrees C because of high depolarization temperature (110 degrees C). Those results unveil the potential of BNT-BA-xNN ceramics for infrared detector applications.