Rayleigh wave hydrogen sensors based on 128∘YX-LiNbO_(3) substrates with WO_(3) sensing layers operating at room temperature are studied.The experimental results indicate that the WO_(3) layers obtained by a sol-gel method have much higher sensitivities because the sensing layers produced by the sol-gel method have small grains and high roughness and porosity.It is also confirmed that in the sol-gel method,keeping WO_(3) solutions at low temperature and/or decreasing the viscosity of the solutions can decrease the grain sizes and increase the hydrogen-absorbability of the sensing layer.Under the optimized preparation conditions,the high sensitivity of the hydrogen sensors at room temperature is obtained,in which 1%hydrogen in natural air induces the frequency shift of 72 kHz at the operating frequency of 124.2 MHz.
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