Quantum-confinement effects on the optical and dielectric properties for mesocrystals of BaTiO3 and SrBi2Ta2O9

We present optical and dielectric quantum-confinement effects for mesocryst als smaller than 30 Angstrom of BaTiO3 and SrBi2Ta2O9 in uniform mesopores of the MCM-41 molecular sieve. For BaTiO3 mesocrystals we observed a bluesh ift in optical absorption edge from 3.0(2) to 3.3(5) eV, and a decrease in dielectric constant maximum temperature from 130 to 55 degrees C. For SrBi2 Ta2O9 mesocrystals we also observed an increase in the optical absorption e dge from 2.7(0) to 4.1(8) eV, and a decrease in the dielectric constant max imum temperature from 320 to 180 degrees C. The observed optical and dielec tric quantum-confinement effects generally agree with the recognized conseq uence of reduced size. (C) 2000 American Institute of Physics. [S0021-8979( 00)08601-1].