Response to "Comment on `Quantum-confinement effects on the optical and dielectric properties for mesocrystals of BaTiO3 and SrBi2Ta2O9\u27"

In this reply, the authors show that the argument by Scott regarding the band gap of bulk SrBi2Ta2O9 (SBT) is not based on concrete evidence. The authors will also show additional data from a Raman study of a powdered SBT sample to prove that the surface of the specimen was not covered by Bi2O3

Response to "Comment on `Quantum-confinement effects on the optical and dielectric properties for mesocrystals of BaTiO3 and SrBi2Ta2O9

In this reply, the authors show that the argument by Scott regarding the band gap of bulk SrBi2Ta2O9 (SBT) is not based on concrete evidence. The authors will also show additional data from a Raman study of a powdered SBT sample to prove that the surface of the specimen was not covered by Bi2O3

Large frequency dependence of lowered maximum dielectric constant temperature of LiTaO3 nanocrystals dispersed in mesoporous silicate

A large frequency dependence of the maximum dielectric constant temperature was observed for LiTaO3 nanocrystals (the diameter 20 Å) dispersed in mesoporous silicate. At the applied field frequency of 100 kHz, the maximum temperatures in the real and imaginary parts were 365 and 345 °C, respectively. The maximum temperature in the real part is apparently lower than the paraelectric–ferroelectric transition temperature (645 °C) of bulk LiTaO3. The maximum temperature in the imaginary part rose from 285 to 420 °C with increasing frequency from 10 to 1000 kHz. Since the bulk LiTaO3 shows no relaxor behavior, such superparaelectric behavior is obviously a consequence of nanominiaturization of LiTaO3 crystal and insignificant cooperative interactions between the nanoparticles

Large frequency dependence of lowered maximum dielectric constant temperature of LiTaO3 nanocrystals dispersed in mesoporous silicate

A large frequency dependence of the maximum dielectric constant temperature was observed for LiTaO3 nanocrystals (the diameter 20 Å) dispersed in mesoporous silicate. At the applied field frequency of 100 kHz, the maximum temperatures in the real and imaginary parts were 365 and 345 °C, respectively. The maximum temperature in the real part is apparently lower than the paraelectric–ferroelectric transition temperature (645 °C) of bulk LiTaO3. The maximum temperature in the imaginary part rose from 285 to 420 °C with increasing frequency from 10 to 1000 kHz. Since the bulk LiTaO3 shows no relaxor behavior, such superparaelectric behavior is obviously a consequence of nanominiaturization of LiTaO3 crystal and insignificant cooperative interactions between the nanoparticles

Frequency-dependent bifurcation point between field-cooled and zero-field-cooled dielectric constant of LiTaO3 nanoparticles embedded in amorphous SiO2

Splitting between the field-cooled dielectric constant and the zero-field-cooled dielectric constant was observed for a diluted system of LiTaO3 nanoparticles (diameter 30 Å) embedded in amorphous SiO2. At the applied field frequency of 100 kHz, the real part of the field-cooled dielectric constant diverged from that of the zero-field-cooled one at 380 °C. The bifurcation point of the history-dependent dielectric constant rose from 310 to 540 °C upon increasing the field frequency from 10 to 1000 kHz. Bulk LiTaO3 powders showed no splitting in the history-dependent dielectric constant and the maximum at 645 °C in the real part of the dielectric constant, despite the variation of frequency. Both the splitting of the history-dependent dielectric constant and the frequency dependence of the bifurcation point suggest that the LiTaO3 nanoparticles with a single-domain structure were in the superparaelectric state as a consequence of insignificant cooperative interactions among the nanoparticles in the diluted system. The energy barrier of 0.9 eV separating two (+p and –p) polarization states corroborated the potential of the LiTaO3 nanoparticle for ultrahigh-density recording media applications

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

We present optical and dielectric quantum-confinement effects for mesocrystals smaller than 30 Angstrom of BaTiO3 and SrBi2Ta2O9 in uniform mesopores of the MCM-41 molecular sieve. For BaTiO3 mesocrystals we observed a blueshift 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 SrBi2Ta2O9 mesocrystals we also observed an increase in the optical absorption edge from 2.7(0) to 4.1(8) eV, and a decrease in the dielectric constant maximum temperature from 320 to 180 degrees C. The observed optical and dielectric quantum-confinement effects generally agree with the recognized consequence of reduced size. (C) 2000 American Institute of Physics

Response to "Comment on `Quantum-confinement effects on the optical and dielectric properties for mesocrystals of BaTiO3 and SrBi2Ta2O9'"

In this reply, the authors show that the argument by Scott regarding the band gap of bulk SrBi2Ta2O9 (SBT) is not based on concrete evidence. The authors will also show additional data from a Raman study of a powdered SBT sample to prove that the surface of the specimen was not covered by Bi2O3

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

We present optical and dielectric quantum-confinement effects for mesocrystals smaller than 30 Angstrom of BaTiO3 and SrBi2Ta2O9 in uniform mesopores of the MCM-41 molecular sieve. For BaTiO3 mesocrystals we observed a blueshift 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 SrBi2Ta2O9 mesocrystals we also observed an increase in the optical absorption edge from 2.7(0) to 4.1(8) eV, and a decrease in the dielectric constant maximum temperature from 320 to 180 degrees C. The observed optical and dielectric quantum-confinement effects generally agree with the recognized consequence of reduced size. (C) 2000 American Institute of Physics