碘化铅钙钛矿太阳能电池综合实验教学研究

以碘化铅钙钛矿太阳能电池制作和光电性能评价为教学内容,进行太阳能电池综合实验课程建设。实验利用多种成膜方法制备氧化锌薄膜、钙钛矿薄膜、空穴传输层薄膜和金电极,最终组装成太阳能电池器件并研究碘化铅浓度对器件光电性能的影响。该综合实验项目将材料制备、材料物理性能、器件评价等理论知识串成知识链并以实验的形式体现。通过该综合实验的训练,构建学生的知识网络,并进一步提高学生的实践能力和思考解决问题的能力。     

无铅钙钛矿的探索性研究

首先对钙钛矿的性质及应用进行了概述,并且对钙钛矿电池的原理和钙钛矿薄膜的制备进行了简要介绍.详细分析了国内外近年对无铅钙钛矿的研究进展,着重分析了使用锡元素和铋元素替代铅元素作为太阳能电池,也简单介绍了诸如二价过渡金属、ⅡA族元素、四价阳离子替代铅元素的研究进展,并对这些替代的元素进行分析,指出优点和不足.最后提出锡元...     

Seeding of Perovskite Lead Magnesium Niobate Crystallization from Pb-Mg-Nb-EDTA Gels

The addition of BaTiO₃ seed particles (50 nm in diameter) to a Pb-Mg-Nb-EDTA solution (where EDTA represents ethylenediamine tetraacetic acid) reduces the formation temperature from 700°C to 600°C during combustion synthesis, because of epitaxial effects. The lower perovskite formation temperature eliminates the formation of pyrochlore at the surface of the precursor bed and allows for the direct crystallization of ∼98% perovskite lead magnesium niobate (PMN) during combustion synthesis. Increasing the nucleation density of the seed particles in the seeded precursor decreases the precursor volume that is associated with each perovskite nucleus and, thus, reduces the PMN particle size from 1 µm to 0.2 µm. The influence of BaTiO₃ seeding is discussed in terms of the thermodynamics of perovskite formation, the influence of BaTiO₃ seed concentration, and epitaxial nucleation.     

碘化铅单晶体生长工艺分析

在坩埚下降法生长PbI2单晶体的过程中,如何解决晶体中的富碘问题是一个研究关键.本文采用坩埚下降法生长出了三种不同颜色的富碘PbI2单晶体.实验中发现:通过合理的选择坩埚在温场中的生长位置,可最大限度的减轻晶体富碘现象,分析了相关工艺,得出了最优工艺方案.结果表明:在适当的工艺条件下,坩埚下降法设备简单,易于操作,是生长PbI2单晶体的优良方法.     

Formation of Lead Magnesium Niobate Perovskite from Niobate Precursors Having Varying Magnesium Content

Formation of lead magnesium niobate (PMN) perovskite phase using a columbite type of precursor together with the addition of excess MgO has been investigated. When MgO and Nb₂O₅ are reacted with 1:1 stoichiometry, a minor amount (}2%) of Mg₄Nb₂O₉ is formed along with the columbite-type phase which in turn could lead to the formation of a minor amount of "free Nb₂O₅" in the precursor. This may be the reason for the formation of small amounts of pyrochlore phase during the synthesis of PMN perovskite from the stoichiometric 1:1 precursor. However, it has been found that the perovskite phase can easily be stabilized by the addition of a large excess of MgO in the precursor, although this leads to additional Mg-Nb-O phase Mg₄Nb₂O₉, besides the columbite-type phase MgNb₂O₆. It has been shown that, after this precursor reacts with PbO to form the PMN perovskite, the excess Mg present in the Mg-rich niobate precursor separates out as MgO, as evidenced by X-ray diffraction, which can be removed by leaching with dilute nitric acid, thus forming pure PMN.     

Synthesis of Lead Titanate: Thermodynamic Modeling and Experimental Verification

A comprehensive thermodynamic model has been developed to determine the reaction conditions favoring hydro-thermal synthesis of lead titanate (PbTiO₃). The model combines standard-state thermodynamic data for solid and aqueous species and an excess Gibbs energy model to account for the nonideality of the solution. The method has been used to generate phase stability diagrams that indicate the ranges of pH and reagent concentrations for which various species predominate in the system at a given temperature and pressure. Also, yield diagrams have been constructed that indicate the concentration, pH, and temperature conditions for which different yields of crystalline PbTiO₃ can be obtained. The stability and yield diagrams have been used to predict the optimum synthesis conditions (e.g., reagent concentrations, pH, and temperature). Subsequently, these predictions have been experimentally verified. As a result, phase-pure perovskite PbTiO₃ has been obtained at temperatures ranging from 413 to 433 K using lead acetate or lead nitrate and commercial TiO₂ powder. Also, PbTiO₃ has been synthesized at lower temperatures (353 T 363 K) by using lead acetate and hydrous (reactive) TiO₂ and calcining the obtained amorphous product.     

Thermodynamic and Kinetic Analyses of the Hydrogenation of Coal from the Mamytskoe Deposit

The kinetic and thermodynamic parameters (the equilibrium degree of reaction, the rates of forward and reverse reactions, the equilibrium constant, the activation energies of forward and reverse reactions, the Gibbs free energy, and the heat effect and entropy of the process) of the hydrogenation of coal from the Mamytskoe deposit of (Republic Kazakhstan) at 380–440°C were calculated with the use of equilibrium kinetic analysis (EKA). It was established that the rate of forward reaction increased whereas the rate of reverse reaction decreased with temperature. The application of the kinetic–thermodynamic model obtained to the hydrogenation of coal from the Mamytskoe deposit facilitated the understanding of the chemical conversion of the organic matter of coal.     

热爆发活化能研究

通过分析影响含能材料热爆发参数的一些因素,指出了热爆发活化能用于全面评价热感度的重要意义.提出了可以通过热爆发活化能把5s爆发点试验与撞击感度试验相关联,并获得特性落高能的对数与热爆发活化能线性相关的线性经验式.     

分布活化能模型计算噻吩在NaY上的脱附活化能

采用程序升温脱附（TPD）技术测定了噻吩在NaY上以不同升温速率升温时的TPD谱图。采用活化能分布模型和一阶微分方法解析了噻吩在NaY上的非等温热重曲线。结果表明,NaY表面对噻吩是均匀的,脱附活化能大约为54 kJ/mol;较低的升温速率有助于提高对TPD曲线的分辨率。     

Dielectric Properties of Complex Perovskite Lead Scandium Tantalate under dc Bias

The weak-field dielectric properties of ordered, disordered, and lead-deficient disordered Pb(Sc_0.5Ta_0.5)O₃ (PST) ceramics (PST-O, PST-D, and PST-DV, respectively) were investigated under various dc-bias conditions. The dc-bias field influences the paraelectric-to-ferroelectric transition in PST-O and the relaxor-to-normal-ferroelectric transition in disordered PST-D. Phase diagrams, with respect to dc bias and temperature, were proposed for ordered and disordered PST materials. A field-induced ferroelectric state that originated from the residual non-ordered regions in PST-O was revealed by analyzing the Curie-Weiss behavior of the materials under bias. It is shown that, in PST-DV, a dc bias cannot induce an abrupt ferroelectric-to-relaxor transition. A dielectric anomaly observed at low temperatures in all three types of PST materials is attributed to a poling process.     

分离过程的能耗分析与选择

在对不同条件下分离过程能耗理论分析的基础上,得到影响分离过程能耗的主要因素,同时对决定分离过程选择的因素进行全面的分析,从而最终确定最佳分离过程。     

Crystallization of Lead Niobate Glass by Mechanical Activation

Mechanical activation-triggered crystallization in PbNb₂O₆-based glass was dependent on the initial presence of nuclei. The crystallization cannot be initiated by mechanical activation in a highly amorphous glass composition quenched from 1350°C where PbNb₂O₆ nuclei did not exist. The steady growth of nanocrystallites of PbNb₂O₆ was observed with an increasing degree of mechanical activation in the glass quenched from 1300°C, where a density of PbNb₂O₆ nuclei existed before mechanical activation. The inability to nucleate in the highly amorphous oxide glass by mechanical activation is consistent with the much higher structural stability as compared with that of metallic glasses, such as Fe-Si-B. The mechanical activation-grown PbNb₂O₆ nanocrystals were 10–15 nm in size as observed using HRTEM and their crystallinities were further improved by thermal aging at an elevated temperature in the range of 550° to 650°C.     

Lead Oxide Coatings on Sol–Gel-Derived Lead Lanthanum Zirconium Titanate Thin Layers for Enhanced Crystallization into the Perovskite Structure

An improved method is described for the sol–gel preparation of PLZT thin layers in the perovskite structure. The method uses a PbO cover coat. Details are reported for the sol-gel processing route and heat-treatment conditions. Through use of this method it is possible to prepare singlephase perovskite material with improved properties. The deleterious effect of additional phases—which are not present when a PbO cover coat is used—is attributed to Pb loss from the surface during thermal processing. Examples are given for PLZT thin layers integrated on Si with and without a PbO cover coat. The dielectric and ferroelectric properties were always found to be superior for coated structures.     

牛粪生物炭的活化及其吸附铅的研究

以Na OH活化牛粪生物炭,分析了活化对牛粪生物炭理化性质的影响,并以生物炭吸附溶液中Pb2+(以0.01 mol/L为背景电解质)。结果表明活化处理能提高生物炭对Pb2+的吸附效果,吸附容量达到192.2 mg/g,相比未活化牛粪生物炭(50.4 mg/g)提高了约4倍。     

Reaction Kinetics of Perovskite Phase Formation in Lead Zinc Magnesium Niobate Ceramics

The reaction kinetics of perovskite Pb[(Zn,Mg)_1/3Nb_2/3]O₃─SrTiO₃ (PZMN–ST) phase formation vary with the phase condition of the starting materials. Basically, the reaction is controlled by a diffusion process with either a fixed number of nuclei or a constant nucleation rate. When the Pb₃Nb₂O₈ (P₃N₂) phase is used as the starting material, the reaction belongs to the former. The P₃N₂ phase acts as a nucleation center and fixes the number of nuclei for perovskite phase formation. If PbO and Nb₂O₅ instead of P₃N₂ are used as starting materials, the nucleation center will be the pyrochlore phase Pb₂Nb₂O₇ or P₃N₂ and is continuously created by the reaction of residual PbO with the formed pyrochlore Pb₃Nb₄O₁₃ phase. In the final stage of PZMN formation, the reaction is mainly through diffusion of ZnO into PMN or Zn-containing PMN. The importance of the pyrochlore phase to perovskite PZMN phase formation is consequently asserted.     

Hydrothermal Precipitation of Lead Zirconate Titanate Solid Solutions: Thermodynamic Modeling and Experimental Synthesis

A previously developed thermodynamic model of hydro-thermal synthesis of ceramic powders has been extended to include cases when solid solutions are formed. The model has been applied to the synthesis of a series of lead titanate zirconate solid solutions PbZr _x Ti_{1– x} O₃ (PZT, 0.46 < x ≤ 0.75). It predicts the optimum conditions (i.e., reagent, concentration, pH, and temperature) for the precipitation of phase-pure homogeneous PZT, provided that the reactants are well mixed. The predictions have been experimentally corroborated using coprecipitated hydrous oxide Zr _x Ti_{1– x} C₂ n H₂O (0.46 < x ≤ 0.75), as a precursor for Ti and Zr and water-soluble lead acetate or nitrate salts as a source for Pb. When mixtures of hydrous oxides ZrO₂· n H₂O and TiO₂· n H₂O were employed as Ti and Zr precursors, independent PbTiO₃ and PbZrO₃ precipitates rather than the PZT solid solutions formed. These results can be rationalized on the basis of reaction kinetics where thermodynamic modeling includes or excludes the possibility of solid-solution formation.     

Nanoarchitectonics of Nanoporous Carbon Materials from Natural Resource for Supercapacitor Application

Nanoarchitectonics of nanoporous carbon materials (NCMs) derived from natural resource; Areca Catechu Nut (ACN) with enhanced electrochemical supercapacitance properties is reported. ACN powder is chemically activated in a tubular furnace at 400?°C and the effect of activating agent sodium hydroxide (NaOH), zinc chloride (ZnCl₂) and phosphoric acid (H₃PO₄) on the textural properties, surface functional groups and electrochemical supercapacitance properties was thoroughly examined. We found that ACN derived NCMs are amorphous in nature comprising of macropores, micropores and hierarchical micro- and mesopore architecture depending on the activating agent. Surface area and pore volume are found in the range 25–1985 m² g^?1 and 0.12–3.42 cm³ g^?1, respectively giving the best textural properties for H₃PO₄ activated NCM. Nevertheless, despite the different chemical activating agent used, all the prepared NCMs showed similar oxygen-containing surface functional groups (carboxyl, carboxylate, carbonyl and phenolic groups). The H₃PO₄ activated NCM showed excellent supercapacitance properties giving a high specific capacitance of ca. 342 F g^?1 at a scan rate of 5 mV s^?1 together with the high cyclic stability sustaining capacitance retention of about 97% after 5000 charging/discharging cycles. Electrochemical supercapacitance properties have demonstrated that the ACN derived novel nanoporous carbon material would be a potential material in energy storage application.     

Gibbs Energy of Formation of Lead Zirconate

The Gibbs energy of formation of zirconia-saturated lead zirconate was determined by emf measurements on the solid state cells
and
at 800 to 1400 K. The results obtained differ significantly from those reported in the literature based on vapor-pressure measurements, using Knudsen effusion and transportation techniques and assuming that the vapor phase consisted entirely of monomeric PbO molecules. A reanalysis of the data obtained in the earlier vapor-pressure studies, using mass-spectrometric measurements on polymeric PbO species in the gas phase, gives Gibbs energies of formation of lead zirconate which are in better agreement with those obtained in this study. Recent electrochemical measurements using CaO-ZrO₂ and PbF₂ solid electrolytes are in good agreement with the present study. The results obtained in this study are also consistent with the phase diagram which shows decomposition of the zirconate to tetragonal zirconia and a liquid phase rich in PbO at 1843 K.     

Energy of Activation and Water Structure

Instances of temperature-dependent apparent energies of activation E_A, observed for hydrolysis reactions, are briefly reviewed, as are recent calculations according to which the presence of a reactant in two forms which are in mobile equilibrium may lead to a temperature-dependent E_A. These calculations are extended to a consideration of the temperature-dependence of the specific heat of activation, and to the possibility of more than two forms being in equilibrium. It is shown in some detail how the equilibrium between broken and intact hydrogen bonds in water may be responsible for observed effects.