Amounts Of MnCO3 Research Articles

Synthesis and luminescence properties of red‐emitting AlN:Mn2+ spherical phosphors

AbstractIn this study, we successfully prepared red‐emitting AlN:Mn2+ spherical phosphors by using nitrogen pressure–assisted carbothermal reduction–nitridation method. The optimum preparation parameters were explored by changing nitrogen pressure, CaF2 content, reaction temperature, and the amount of MnCO3. It was confirmed that uniform spherical shape, large particle size, less impurity content, and suitable Mn2+ concentrations could effectively enhance the luminous intensity of AlN:Mn2+ phosphors. The structural compositions of the AlN:Mn2+ phosphors were characterized by X‐ray diffraction and X‐ray photoelectron spectroscopy, indicating that Mn2+ ions were successfully doped into AlN lattice by substitution of Al3+ ions, thus providing the red‐emitting luminescence centers. Based on the experimental results, we further proposed the underlying growth mechanism of spherical AlN phosphors. It was suggested that an adequate amount of liquid Ca‐aluminates was essential to achieve uniform spherical morphology and high fluorescence efficiency.

Effect of MnCO<sub>3</sub> Doping on Microstructure and Electrical Properties of PSZT Ceramics

The effect of manganese doping on microstructure, piezoelectric and electromechanical properties of Pb0.94Sr0.06(Zr0.52Ti0.48)O3 (PSZT) ceramics has studied. The PSZT ceramics doped MnCO3 concentration in the region of 0-1.0 mol% were prepared by a solid-state reaction and conventional sintering process. Phase identification showed the formation of single phase perovskite structure in all compositions. Microstructure and fracture behavior were observed by scanning electron microscopy (SEM). The fracture behavior demonstrated the change of fracture type from trangranular to mix of trans-and inter-granular type with increasing the amount of MnCO3. Dielectric constant (K), d33 and kp were increased when higher amount of MnCO3 was doped. In addition, the mechanical quality factor (Qm) was highest at 0.1 mol% MnCO3 doping in PSZT ceramics.

Effect of Mn, Si on Varistor-Dielectric Characteristics of Nb-doped SrTiO<sub>3</sub> Ceramics

The varistor-dielectric characteristics of SrTiO3 ceramics with various amounts of MnCO3 and SiO2 additives was studied. The experimental results show that , with the increase of added amounts of MnCO3, the resistivity (ρ), nonlinear coefficient (α) and varistor voltage (V10mA) increase firstly and then decrease while the dielectric constant (ε) and dielectric loss (tgδ) decrease firstly and then increase. The best added amount of SiO2 is 0.4wt% because the electrical properties of SrTiO3 ceramics drop when x(SiO2)>0.4wt%.The SrTiO3 based ceramic, with the doping of 0.5mol%Nb2O5+0.5mol%MnCO3+0.4wt%SiO2, the better microstructure and electrical properties can be obtained.

Dielectric Properties of (Bi<sub>1/2</sub>Na<sub>1/2</sub>)TiO<sub>3</sub>-SrTiO<sub>3</sub> Ferroelectric Ceramics

Ferroelectric properties of (Bi1/2Na1/2) TiO3-SrTiO3 were studied. The dielectric properties were measured at 1KHz. It was found that the dielectric constants are improved with the increase of additive amount of BNT. If the amount continues increasing, the properties become worse, the optimum dielectric constant of the samples can reach 4300. When the proportion of (Bi1/2Na1/2)TiO3: SrTiO3 is 65:35, with the increase of additive amount of MnCO3, the Curie temperature descends obviously. The dielectric constant increased at beginning and dropped sharply when the amount of MnCO3 exceeds 1.1wt%.

Influences of MnCO<sub>3</sub> Doping on Processing Parameters and Dielectric Properties of ZnNb<sub>2</sub>O<sub>6</sub> Microwave Ceramics

MnCO3 was added into ZnNb2O6 ceramics to obtain excellent microwave dielectric properties. The samples were prepared by conventional solid-state reaction method. The effects of the amount of MnCO3 on sintering temperatures, ceramic densities and contraction were systematically investigated. The crystalline structure of ceramic body was analyzed by XRD. The ceramic microstructure was observed by SEM. The dielectric properties of ZnNb2O6 ceramics were measured by a vector network analyzer at microwave frequency, which showed: er = 22.65, Q×f = 36700 GHz (loaded value) and tf = -40 ppm/°C.

Preparation of a modified (Pb,Ca)TiO3 piezoelectric ceramics with binary complex elements substitution in B-site

Preparation of a modified (Pb,Ca)TiO3 with (Zn1/2W1.2) (Ni1/2Nb1/2) substitution in B-site had been studied. Adding suitable amounts of MnCO3 in this modified PbTiO3 piezoelectric ceramics, the material performances could be improved further. Optimized fabricating procession had also been investigated. Study showed that the modified (Pb,Ca)TiO3 piezoelectric ceramics had large anisotropy high mechanical quality factor and curie temperature lower dielectric constant and loss. The microstructure of the ceramics and a kind of micro-domain had been observed by XRD and TEM.