Effect of annealing temperature on the sol-gel derived Pb(Zr_0.3Ti_0.7)O₃ thin films for pyroelectric application

Lead zirconate titanate thin films by a sol-gel method are deposited on platinum coated silicon wafer for pyroelectric application. Annealing temperature is varied between 560 and 700 °C in order to optimize the detectivity figure of merit F_d = p/[c(ε_rε₀ tan δ)^1/2] (where p is pyroelectric coefficient, c is volume specific heat, ε_r is the relative dielectric constant, ε₀ is dielectric constant of free space and tan δ is the dielectric loss tangent). Only perovskite crystalline structure are observed in all the films annealed in this temperature range. It is found that higher annealing temperature is beneficial for better pyroelectric property. The measured pyroelectric coefficient is increased from 220 μC m^-2 K^-1 at 560 °C annealing temperature to 300 μC m^-2 K^-1 at 700 °C annealing temperature. But dielectric constant is also found to increase with annealing temperature from 310 at 560 °C to 560 at 700 °C, which impairs the value of detectivity figure of merit. Another important parameter is dielectric loss tangent, which is found to decrease with annealing temperature from 0.025 at 560 °C to 0.011 at 700 °C. The calculated detectivity figure of merit increases with increasing annealing temperature from 560 to 640 °C and decreases with further increasing annealing temperature. The optimized annealing temperature is determined to be 640 °C, and the detectivity figure of merit is 16.6 × 10^-6 Pa^-1/2.