Zhang Shuren

Permittivity and its temperature dependence in hexagonal structure BN dominated by the local electric field

This paper presents an analysis of the local electric field in hexagonal boron nitride (h-BN) by introducing a modified parameter. Based on the determination of the modified parameter of h-BN, the revised Lorenz equation is developed. Then the permittivity at high temperature and in the microwave frequency is investigated. In addition, this equation is derived for evaluating the temperature coefficient of the permittivity of h-BN. The analyses show that the permittivity increases with increasing temperature, which is mainly attributed to the positive temperature coefficient of the ionic polarizability.

Effect of Mn2+ doping on the temperature coefficient of capacitance of TiO2/SiO2-doped BaTiO3 ceramics

The effect of Mn2+ on the temperature coefficient of capacitance (TCC) of TiO2/SiO2-doped BaTiO3 ceramics has been investigated. The experiment has shown that the high temperature peak of TCC exhibited a continuous enhancement when Mn2+ concentration increased and X8R specification was gradually met. The secondary phase Ba2TiSi2O8 was found in all samples. SEM and XRD analyses have proved that Mn2+ could depress the crystallization of TiO2/SiO2 in BaTiO3 ceramics. The microstrain study through MAUD analysis depicted that the high temperature peak of TCC was dependent on the microstrain of samples to a certain extent. The Mn2+ could be a useful dopant for ameliorating the TCC of TiO2/SiO2-doped BaTiO3 ceramics.

PRECURSOR-MONOMER METHOD OF SOL-GEL FOR FABRICATION PT/PZT/PT FERROELECTRIC FILMS

ABSTRACT Lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (PZT) thin films was successfully deposited on Pt(111)/Ti/SiO2/Si(100) substrates by a new modified sol-gel technique: precursor-monomer method. In this process three separated Pb2 +, Zr4 +, Ti4 + precursor-monomers and metal chelating agents were mixed together to prepare PZT sol-solution (precursor). The precursor-monomer method has several advantages over conventional sol-gel methods, including easy change the atomic ratio of Pb2 +/Zr4 +/Ti4 + and doping metallic ions, rapid PZT precursor synthesis, low processing temperature, without dry condition and distillation, long storage period, simplicity and low cost, etc. The paper investigated the effects of hydrolysis degree on the stability of PZT precursor, and it was found that the sample with 12.5% (v/v) adding water had the longest storage time. The inference of lead titanate (PbTiO3, PT) seeding layers on the microstructures, surface morphologies and ferroelectric properties of PZT films has also been systematically examined. We found that PZT films with PT/PZT/PT structure had lower perovskite phase crystallization temperature, larger grain size, better microstructure and ferroelectric properties as compared with no PT seeding layers films.