Polymer nanocrystal composites were fabricated by embedding polyvinylidene fluoride (PVDF) with K0.5Na0.5NbO3 (KNN) nanocrystallites of different volume fraction using the hot-pressing technique.For comparison,PVDF-KN...Polymer nanocrystal composites were fabricated by embedding polyvinylidene fluoride (PVDF) with K0.5Na0.5NbO3 (KNN) nanocrystallites of different volume fraction using the hot-pressing technique.For comparison,PVDF-KNN microcrystal composites of the same compositions were also fabricated which facilitated the studies of the crystallite size (wide range) effect on the dielectric and piezoelectric properties.The structural,morphological,dielectric,and piezoelectric properties of these nano and micro crystal composites were investigated.The incorporation of KNN fillers in PVDF at both nanometer and micron scales above 10 vol％ resulted in the formation of polar β-form of PVDF.The room temperature dielectric constant as high as 3273 at 100 Hz was obtained for the PVDF comprising 40 vol％ KNN nanocrystallites due to dipole-dipole interactions (as the presence of β-PVDF is prominent),whereas it was only 236 for the PVDF containing the same amount (40 vol％) of micron-sized crystallites of KNN at the same frequency.Various theoretical models were employed to predict the dielectric constants of the PVDF-KNN nano and micro crystal composites.The PVDF comprising 70 vol％ micron-sized crystallites of KNN exhibited a d33 value of 35 pC/N,while the nanocrystal composites of PVDF-KNN did not exhibit any piezoelectric response perhaps due to the unrelieved internal stress within each grain,besides the fact that they have less domain walls.展开更多
CaCu_(3)Ti_(4)O_(12)(CCTO)ceramics which has perovskite structure gained considerable attention due to its giant permittivity.But it has high tan(0.1 at 1 kHz)at room temperature,which needs to be minimized to the le...CaCu_(3)Ti_(4)O_(12)(CCTO)ceramics which has perovskite structure gained considerable attention due to its giant permittivity.But it has high tan(0.1 at 1 kHz)at room temperature,which needs to be minimized to the level of practical applications.Hence,TeO_(2) which is a good glass former has been deliberately added to CCTO nanoceramic(derived from the oxalate precursor route)to explore the possibility of reducing the dielectric loss while maintaining the high permittivity.The structural,morphological and dielectric properties of the pure CCTO and TeO_(2) added ceramics were studied using X-ray diffraction,Scanning Electron Microscope along with Energy Dispersive X-ray Analysis(EDX),spectroscopy and Impedance analyzer.For the 2.0 wt.%TeO_(2) added ceramics,there is a remarkable difference in the microstructural features as compared to that of pure CCTO ceramics.This sample exhibited permittivity values as high as 7387 at 10 KHz and low dielectric loss value of 0.037 at 10 kHz,which can be exploited for the high frequency capacitors application.展开更多
The glasses in the system(100-x)TeO_(2)-xCaCu_(3)Ti_(4)O_(12),(x=0.25 mol.%to 3 mol.%)were fabricated.The color varied from olive green to brown as the CaCu_(3)Ti_(4)O_(12)(CCTO)content increased in TeO_(2) matrix.The...The glasses in the system(100-x)TeO_(2)-xCaCu_(3)Ti_(4)O_(12),(x=0.25 mol.%to 3 mol.%)were fabricated.The color varied from olive green to brown as the CaCu_(3)Ti_(4)O_(12)(CCTO)content increased in TeO_(2) matrix.The X-ray powder diffraction and differential scanning calorimetric analyses that were carried out on the as-quenched samples confirmed their amorphous and glassy nature respectively.The dielectric constant and loss in the 100Hz1MHz frequency range were monitored as a function of temperature(50-400℃).The dielectric constant(ε′_(τ))and the loss(D)increased as the CCTO content increased in TeO_(2) at all the frequencies and temperatures under investigation.Further,the ε′_(τ) and D were found to be frequency-independent in the 50-200℃ temperature range.The value obtained for the loss at 1MHz was 0.0019 which was typical of low loss materials,and exhibited near constant loss(NCL)in the 100Hz-1MHz frequency range.The electrical relaxation was rationalized using the electric modulus formalism.These glasses may be of considerable interest as substrates for high frequency circuit elements in conventional semiconductor industries owing to their high thermal stability.展开更多
文摘Polymer nanocrystal composites were fabricated by embedding polyvinylidene fluoride (PVDF) with K0.5Na0.5NbO3 (KNN) nanocrystallites of different volume fraction using the hot-pressing technique.For comparison,PVDF-KNN microcrystal composites of the same compositions were also fabricated which facilitated the studies of the crystallite size (wide range) effect on the dielectric and piezoelectric properties.The structural,morphological,dielectric,and piezoelectric properties of these nano and micro crystal composites were investigated.The incorporation of KNN fillers in PVDF at both nanometer and micron scales above 10 vol％ resulted in the formation of polar β-form of PVDF.The room temperature dielectric constant as high as 3273 at 100 Hz was obtained for the PVDF comprising 40 vol％ KNN nanocrystallites due to dipole-dipole interactions (as the presence of β-PVDF is prominent),whereas it was only 236 for the PVDF containing the same amount (40 vol％) of micron-sized crystallites of KNN at the same frequency.Various theoretical models were employed to predict the dielectric constants of the PVDF-KNN nano and micro crystal composites.The PVDF comprising 70 vol％ micron-sized crystallites of KNN exhibited a d33 value of 35 pC/N,while the nanocrystal composites of PVDF-KNN did not exhibit any piezoelectric response perhaps due to the unrelieved internal stress within each grain,besides the fact that they have less domain walls.
基金The management of Central Power Research Institute is acknowledged for the financial support(CPRI Project No.R-DMD-01/1415).
文摘CaCu_(3)Ti_(4)O_(12)(CCTO)ceramics which has perovskite structure gained considerable attention due to its giant permittivity.But it has high tan(0.1 at 1 kHz)at room temperature,which needs to be minimized to the level of practical applications.Hence,TeO_(2) which is a good glass former has been deliberately added to CCTO nanoceramic(derived from the oxalate precursor route)to explore the possibility of reducing the dielectric loss while maintaining the high permittivity.The structural,morphological and dielectric properties of the pure CCTO and TeO_(2) added ceramics were studied using X-ray diffraction,Scanning Electron Microscope along with Energy Dispersive X-ray Analysis(EDX),spectroscopy and Impedance analyzer.For the 2.0 wt.%TeO_(2) added ceramics,there is a remarkable difference in the microstructural features as compared to that of pure CCTO ceramics.This sample exhibited permittivity values as high as 7387 at 10 KHz and low dielectric loss value of 0.037 at 10 kHz,which can be exploited for the high frequency capacitors application.
基金The management of Central Power Research Institute is acknowledged for the financial support(CPRI Project No.R-DMD-01/1415).
文摘The glasses in the system(100-x)TeO_(2)-xCaCu_(3)Ti_(4)O_(12),(x=0.25 mol.%to 3 mol.%)were fabricated.The color varied from olive green to brown as the CaCu_(3)Ti_(4)O_(12)(CCTO)content increased in TeO_(2) matrix.The X-ray powder diffraction and differential scanning calorimetric analyses that were carried out on the as-quenched samples confirmed their amorphous and glassy nature respectively.The dielectric constant and loss in the 100Hz1MHz frequency range were monitored as a function of temperature(50-400℃).The dielectric constant(ε′_(τ))and the loss(D)increased as the CCTO content increased in TeO_(2) at all the frequencies and temperatures under investigation.Further,the ε′_(τ) and D were found to be frequency-independent in the 50-200℃ temperature range.The value obtained for the loss at 1MHz was 0.0019 which was typical of low loss materials,and exhibited near constant loss(NCL)in the 100Hz-1MHz frequency range.The electrical relaxation was rationalized using the electric modulus formalism.These glasses may be of considerable interest as substrates for high frequency circuit elements in conventional semiconductor industries owing to their high thermal stability.
