Ren Bo Yang

Ferroelectric and Piezoelectric Properties of (1-x)BaTi0.8Zr0.2O3-xBa0.7Ca0.3TiO3 Ceramics Prepared by Sol-Gel Technique

The(1-x)BaTi0.8Zr0.2O3-xBa0.7Ca0.3TiO3 ceramics have been prepared by sol-gel technique, where x is from 0.2 to 0.6. It reveals that the dense ceramics can be obtained when the sintered temperature is above 1250°C. It is lower than that of solid state reaction ceramics. In particular, when x=0.3, at which is near the MPB composition, the ferroelectric and piezoelectric properties are more excellent than the others. The maximum dielectric constant is above 9000, which can be observed in the butterfly shape curves of dielectric constant as a function of electric field. The maximum piezoelectric coefficient d33 can reach 400 pm/V, and it is obtained from the piezoelectric response loops.

Enchancement of Mechanical Properties in BaTiO3 Ferroelectric Thin Films

Surface structure and mechanical properties of BaTiO3 thin films prepared by sol-gel process were investigated by XP-2 profiler and nano-indention. The results indicated that the thickness of thin films got thicker with sintering temperature and the thickness-increasing rate differ from different solvent. The hardness and elastic modulus were enhanced due to the presence of residual stress which was compression and probably induced by fabrication method. The maximum hardness is 9.98GPa when the Young’s modulus is 127.41GPa with ethanol as solvent sintered at 1000oC.

Ferroelectric and Dielectric Properties of La2O3-Doped BaTiO3 Ceramics

The different concentration La2O3-doped BaTiO3 ceramics were prepared by sol-gel method. The ferroelectric and dielectric properties of the ceramics are characterized by TF analyzer 2000. With the increased amount of La2O3-doped, the dielectric constant increase gradually, when the sintering temperature is 1250 °C, the dielectric constant has reached 4648 for La2O3 with 0.4％-doped. With the temperature increased the dielectric constant of La-BaTiO3 increase gradually, when the sintering temperature is 1290 °C, the dielectric constant has reached 7066 for La2O3 with 0.4％-doped.

Preparation and Ferroelectric Properties of Sol-Gel Derived (Ba0.95Ca0.05)TiO3 Ceramics

Ba0.95Ca0.05)TiO3 (BCT) ferroelectric ceramics were prepared from powders synthesized using a sol–gel process. Structural evolution of the BCT dry gels are investigated by thermal gravimetric analysis differential scanning calorimetry. It is found that BCT crystallites can be formed before 800°C. Well-sintered samples are synthesized at 1320°C for 2h. The crystal structure of the BCT ceramics is studied by XRD and ferroelectric properties of the ceramics are characterized by TF analyzer 2000. The Curie temperature Tc of the BCT ceramics is at about 130°C. The maximum dielectric constant (εr) reaches about 13678 at 130°C and hysteresis loops are measured with the temperature range from 25°C to 150°C.

Electrical Properties of La2O3-Doped BaTiO3 Ceramics

Hysteresis loop and dielectric properties of lead-free BaTiO3-La2O3 piezoelectric ceramics and BaTiO3 ceramic compared with pure BaTiO3 has been systematically studied. The amount of La2O3 addition ranged from 0.3~0.5mol% by controlling the sintering temperature. Dielectric properties of BaTiO3-La2O3 were promoted after the addition of La2O3, the maximum value of dielectric constant reached 8,624, recently. The role of La2O3 on the solid-state sintering of BaTiO3 is discussed on the basis of the solid-solution defect model.

Preparation and Ferroelectric Properties of (Ba0.7Ca0.3)TiO3 Ceramics

(Ba0.7Ca0.3)TiO3 (BCT) powders and ceramics have been prepared by sol-gel technique. Structural evolution of the BCT dry gels are investigated by thermal gravimetric analysis–differential scanning calorimetry. It is found that BCT crystallites can be formed before 800 . Well-sintered samples are synthesized at 1260 for 2h. The crystal structure of the BCT powders is studied by XRD and ferroelectric properties of the ceramics are characterized by TF analyzer 2000. The Curie temperature Tc of the BCT ceramics is at about 125 . The maximum dielectric constant (εr) reaches about 4851 at 125 and hysteresis loops are measured with the temperature range from 25 to 150 .

Preparation and Characterization of (Ba0.88Ca0.12)(Zr0.12Ti0.88)O3 Powders and Ceramics Produced by Sol-Gel Process

The (Ba0.88Ca0.12)( Zr0.12Ti0.88)O3 powders and piezoelectric ceramics were prepared by sol-gel process. The reaction process was analyzed with the help of thermo gravimetric and differential scanning calorimetry. X-ray diffraction characterized results showed that the structure of the (Ba0.88Ca0.12)( Zr0.12Ti0.88)O3 powders was perovskite structure and the particle size was approximately 37nm. Piezoelectric measurements revealed that Curie temperature and the maximum piezoelectric coefficient d33 is 95°C and 215pm/V, respectively.

Structure and Dielectric Tunability of Ba (Ti1-yZry)O3 Ferroelectric Ceramics

Barium zirconate titanate Ba(Ti1-yZry)O3 (BZT, y = 0.02, 0.07, 0.09, 0.12, 0.15) ceramics have been prepared by sol–gel process. All the BZTx ceramics exhibited perovskite phase detected by X-ray diffraction, and the diffraction peaks shift to lower angle with increasing the content of Zr. Dielectric susceptibilities are up to 15500, and tunability up to 74.9% under electric field 6.8 kV/cm at 100 Hz.