Min-Chul Chae

Preparation and dielectric properties of Pb[(Mg1/3Ta2/3), (Zn1/3Nb2/3)]O3 relaxor ceramics

Abstract Powders of Pb(Mg1/3Ta2/3)O3-Pb(Zn1/3Nb2/3)O3 ceramic system were prepared by a B-site precursor method. Perovskite phase contents and lattice parameters of the system are reported. Weak-field radio-frequency dielectric constants and losses of sintered samples were investigated as functions of composition, temperature, and frequency. Dielectric relaxation and diffuse phase transition behaviors were characterized. Microstructures were examined and correlated with dielectric characteristics.

Stabilization of perovskite phase and enhancement in dielectric properties by substitution of Pb(Mg1/3Nb2/3)O3 to Pb(Zn1/3Ta2/3)O3

Abstract Stabilization of a perovskite structure in the Pb(Zn1/3Ta2/3)O3-Pb(Mg1/3Nb2/3)O3 system was attempted. System powders were prepared by reacting PbO and pre-synthesized B-site precursor compositions. Perovskite phase developments were studied as functions of substituent amounts and heat-treatment stages. Formation tendencies of perovskite/pyrochlore structures were discussed in terms of electronegativity difference and tolerance factor. Dielectric properties of the system ceramics were investigated, with further analyses on diffuseness characteristics in the dielectric constant spectra.

Preparation of Pb(Mg1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3 ceramics by the B-site precursor method and dielectric characteristics

Powders in the Pb(Mg1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3 system, with a high perovskite yield, were prepared by a B-site precursor method. PbO was added to pre-reacted B-site components of Mg1-xZnxNb2O6 solid solution, which was further calcined to form a perovskite structure. Perovskite phase contents and lattice parameters were obtained from X-ray analyses. Weak-field low-frequency dielectric constants and losses of sintered pellets were measured as functions of composition, temperature and frequency. Dielectric relaxation behaviours were investigated in terms of diffuseness coefficients. Microstructures were observed to correlate with other characteristics.

Perovskite formation by B-site precursor method and dielectric characteristics of Pb[Mg1/3(Ta,Nb)2/3]O3 ceramic system

Abstract Phase-pure perovskite powders of Pb(Mg1/3Ta2/3)O3-Pb(Mg1/3Nb2/3)O3(PMT-PMN) system were prepared through a B-site precursor route. Maximum dielectric constants and Curie temperatures (@1kHz) of PMT and PMN were 8,700 and 20,000 at -85° and -5°C, respectively. Both PMT and PMN showed relaxor behaviours. Diffuse characters of dielectric constant spectra in the paraelectric region were thoroughly explored.

Effect of Zn substitution on dielectric responses of 0.2PMT·0.8PMN ceramics

Abstract Phase developments and lattice parameters of a perovskite structure as well as dielectric responses in a Pb[(Mg 1/3 Ta 2/3 ) 0.2 (Mg 1/3 Nb 2/3 ) 0.8 ]O 3 system with Zn substitution for Mg are reported. Perovskite developments were investigated by X-ray diffractometry, from which phase yields and lattice parameters with compositional change were determined. Weak-field dielectric constant values of the entire system ceramics were measured under low-frequency conditions. Phase transition modes reflected in the dielectric constant spectra were further analyzed closely to explore diffuseness characteristics.

Dielectric properties of ceramics (z=0.4,0.6)

In an attempt to stabilize a perovskite structure in PbZn13Ta23O3, Mg (40 and 60 at.%) and Nb (full composition range) were simultaneously substituted for Zn and Ta, respectively. B-site precursor compositions were synthesized separately, followed by PbO addition, in order to promote perovskite formation, whose content has been determined by X-ray diffraction. Low-frequency dielectric responses of the ceramic system were investigated under weak-field conditions. Effects of substituent concentration on the perovskite formation and dielectric properties are discussed.

Preparation of Mg-modified Pb[Zn1/3(Ta0.4Nb0.6)2/3]O3 ceramics and dielectric characteristics

Mg (full composition range) and Nb (60 at %) were simultaneously substituted into Pb(Zn1/3Ta2/3)O3, in an attempt to stabilize the perovskite structure. System powders were prepared using a B-site precursor method in order to enhance perovskite formation. The developed structures were examined by X-ray diffraction, from which perovskite phase yields as well as lattice parameters of the pyrochlore and perovskite were determined. Low-frequency dielectric responses of the ceramics were investigated. Phase transition modes (reflected in the dielectric constant spectra) were further analyzed in terms of diffuseness parameters.

Phase development and dielectric characteristics of the Pb(Mg1/3Ta2/3)O3-modified Pb[(Zn1/3Ta2/3),(Mg1/3Nb2/3)]O3 system

Abstract The effects of Pb(Mg 1/3 Ta 2/3 )O 3 substitution to a multiple-octahedral system Pb[(Zn 1/3 Ta 2/3 ),(Mg 1/3 Nb 2/3 )]O 3 on perovskite phase development and dielectric characteristics are reported. Selected composition powders of the modified system were prepared using a B-site precursor method. Development of the B-site precursor and perovskite phases were investigated by X-ray diffraction. Low-frequency weak-field dielectric properties of sintered pellets were examined. Phase transition modes reflected in the dielectric constant spectra were further analyzed in terms of diffuseness parameters.

Perovskite formation and dielectric properties of Pb[(Mg1/3Ta2/3)0.8(Zn1/3Ta2/3)0.2]O3 ceramics with Nb substitution for Ta

Abstract Powders of a Pb[(Mg 1/3 Ta 2/3 ) 0.8 (Zn 1/3 Ta 2/3 ) 0.2 ]O 3 system with Nb substitution for Ta were prepared using a B-site precursor method. Phase formation yields as well as lattice parameters of the perovskite structure in the system compositions were determined by X-ray diffraction. Dielectric responses of the ceramics were monitored at weak-field low-frequency conditions. The dielectric constant spectra were further analyzed for diffuseness characteristics of the phase transition mode. Microstructures of the sintered specimens were also examined.

Phase developments in Pb[(Mg,Zn)1/3(Ta0.8Nb0.2)2/3]O3 and dielectric properties

Abstract Pb[Zn 1/3 (Ta 0.8 Nb 0.2 ) 2/3 ]O 3 ceramics with Mg substituted for Zn were prepared and characterized. Phases developed in powders of this system (prepared via a B-site precursor route) were examined by X-ray diffractometry, from which perovskite formation yields were determined. Weak-field dielectric responses of ceramics in this system were studied as functions of the composition and measurement frequency.