Solar selective coating having higher thermal stability useful for harnessing solar energy and a process for the preparation thereof

The disclosure provides an improved solar selective multilayer coating having higher thermal stability and a process therefor. According to the disclosure, a tandem stack of three layers of TiAlN, TiAlON and Si3N4 is deposited on metal and non-metal substrates using a planar reactive magnetron sputtering process. The first two layers function as the absorber and the third antireflection layer further enhances the coating's absorptance. The solar selective coatings were annealed in air and vacuum to test the thermal stability at different temperatures and durations. The coatings deposited on copper substrates are stable in air up to a temperature of 625° C. and exhibit higher solar selectivity and these coatings also show no change in the absorptance and the emittance values even after vacuum annealing at 600° C. for 3 hours. The solar selective coatings exhibit high hardness, high oxidation resistance, chemical inertness and stable microstructure.