Iranian Journal of Crystallography and Mineralogy
Year:2002 | Volume:10 | Issue:2|Papers Count:8

In this research, the decrease of sintering temperature of piezoelectric ceramic PZT, P(Zr0.53Ti0.47)O3 was investigated by adding different percent of NiO impurity to the initial materials and then calcined at l000°C. X-ray diffraction results from different samples proved the formation of two phases including tetragonal and rembohedral structure. In addition, formation of a new cubic phase of NiO between grains was approved. Then samples were sintered at 1100°C and electrical and piezoelectrical experiments were done on them. Microstructure of samples was investigated by SEM. The results of SEM showed that samples with 10 percent impurity have maximum size of grain and porosity.  

In this paper, ferroelectric thin films, described by an ising model in a transverse field, have been studied under the mean-field approximation. We discuss a thin film composed of N-layer film of simple cubic symmetry with nearest-neighbor exchange in which the exchange strength and transverse field are assumed to be different from the bulk values in Ns surface layers, and we derive and illustrate expression for specific heat and susceptibility. In such films, the Curie temperature can shift to either lower or higher temperature compared with the corresponding bulk value. If the surface exchange strength is strong enough, there is still a phase transition to ferroelectricity even when the transverse field is larger than the bulk critical value. The bulk peak of the specific heat becomes a discontinuity at the film curie temperature. There is a rounded peak at the bulk curie temperature if the surface exchange strength is higher than the critical value. The film susceptibility still diverges at the film Curie temperature, as does the bulk susceptibility, but its magnitude is reduced. Also there is a rounded peak at the bulk Curie temperature when the surface exchange strength exceeds the critical value. The bulk related character of the specific heat and susceptibility is less pronounced and the surface - related character is more pronounced when the film thickness is small, or the surface – layer number is large.    

Abstract: The phase formation and solid solution system of Lithium Iron (II) Phosphate and Lithium Manganese (II)Phosphate using solid state reaction have been studied. The observed phases were identified by X-ray powder diffraction and electrochemical measurements. The synthesized phases show X-ray diffraction spectra typical of orthorhombic symmetry, space group Pmnb and are closely related to that of the olivine system. A relation between the amount of δ in the system Lix (Fe1-δ-Mn δ) PO4 and the diffraction lines 2θ (hk1) has been found. The electrochemical and chemical analyses of the charge - discharge reaction mechanism of the orthorhombic type Lix (Fe1-δ-Mn δ)PO4 , 0< x<l, showed that this compounds can be used as cathode material for lithium rechargeable batteries.  

Zeolites are hydrated crystalline aluminosilicates of alkali and alkaline earth cations. Their three dimensional framework consist of [SiO4]- and [AlO4]- tetrahedra. Beside their low price and abundance, three main properties of zeolites i.e: adsorption, ion exchange and catalytical properties promote their versatile industrial applications. In Iran, lack of a systematic and comprehensive research on the characterization of natural zeolites causes these valuable minerals to be relatively unknown. The aim of this research is to characterize some of the Iranian natural zeolites by means of thermal analysis methods including thermogravimetry (TG), and derivative thermogravimetry (DTG). In some cases, X-ray diffractometry and chemical analysis were used as complementary methods.  

Existence and frequency of clay minerals is useful for reconstruction of paleoenvironment, because each mineral is formed and stabilized in special condition. The objective of this study was to identify clay minerals and their genesis in two paleosols from Isfahan and Charmahal-Bakhtiari. Through field observations and physico-chemical analysis, some horizons in these soils were selected for mineralogical studies. Soil and parent material samples were analyzed by XRD after necessary pretreatments. A few of samples were studied by scanning electron microscope and infrared spectrometer. The results indicate that mineralogical composition in surface horizon of Sepahanshahr profile is similar to parent material, whereas in the underlying paleohorizons palygorskite predominates. Lack of palygorskite in parent material on one hand and elongated shape of this mineral accompanied by calcite and gypsum in the paleohorizons on the other hand show that, it has formed pedogenicaly. In the soil surface of Emam_Gheis soil, the composition of clay minerals is also similar to parent material, but chlorite has been converted to vermiculite and subsequently to smectite, due to relatively high precipitation in this area. Presence of high amount of smectite in buried paleosol of Emam- Gheis probably indicates moister regime in the past.  

Intrusion of the Kalaybar nepheline syenite into the Cretaceous pelitic and calcareous sediments has produced a thermal aureole up to 1km thick. Six mineralogical zones are developed in the pelitic rocks with minerals such as cordierite, K feldspar, sillimanite and corundum. Chemically suitable rocks are partially melted in response to the heat from the pluton. Five mineralogical zones are developed in the calc-silicate rocks with minerals such as tremolite, diopside, garnet, scapolite, wollastonie and vesuvianite. A petrogenetic grid was used for pelitic rocks to put constraints on pressure of metamorphism. Intersection of the reaction curves on the grid indicates a pressure of ca. 3 kbar for the contact metamorphism in the Kalaybar aureole. Calculation of the positions of the reaction curves for the calc-silicate rocks assuming unit activity for all phases, and plotting them on T-XCO2 diagrams shows that the XCO2 is about 0.2 and it is almost independent of pressure. Calculation of the position of the reaction curves assuming dilution of the phases due to solid-solution gives the similar results indicating that the actual composition of the fluid had a XCO2 about 0.2 during peak metamorphic condition. The temperature was 700-750°C for sillimanite zone in pelites and 600-700°C for wollastonite-vesuvianite zone in the calc-silicates.  

The reaction between LH2, [pyda.H2] [pydc], (pyda = 2, 6 - pyridinediamine and pydc. H2 = 2, 6 - pyridinedicarboxylic acid), ligand with palladium (II) chloride leads to the formation of  [pyda.H]2 [PdCI4]. The crystal structure of the compound was determined by X-ray diffraction. The crystal system is triclinic with space group Pī and one molecule per unit cell. The unit cell dimensions are a = 6.900(3) Ǻ, b = 7.898(3) Ǻ, c = 8.025 (3) Ǻ, with α = 103.302(14) °, β = 104.068(14)° and γ= 92.415(12)°.The final R value is 0.0602 for 1988 reflections. The  resumably of the formation [pyda.H][Pd(pydc)(pydc.H)], [Pd(pydc.H)2] and [pyda.H]CI species, was studied by IR, ESI/MS, 1H NMR, 13C NMR spectroscopy, and elemental analysis.