Crystal Engineering最新文献_第6页

‘A’ cation control of perovskite properties 钙钛矿性质的“A”阳离子控制

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00054-0

J.P. Attfield

{"title":"‘A’ cation control of perovskite properties","authors":"J.P. Attfield","doi":"10.1016/S1463-0184(02)00054-0","DOIUrl":"10.1016/S1463-0184(02)00054-0","url":null,"abstract":"<div>The materials properties of many ABO3 perovskites result primarily from the B cations, but are tuned by the cation(s) at the A sites. Notable examples are ferroelectric titanates, magnetoresistive manganites, and layered A2BO4 type superconducting cuprates. The A cation control of these properties can be described through a simple ionic approach by considering the sizes and charges of the A cations. The size control is approximated well by the mean A cation radius, equivalent to the traditional perovskite tolerance factor, and the size variance which describes the mismatch in ionic radii. Studies in recent years have shown that the latter term is extremely significant; ferroelectric, ferromagnetic, superconducting and structural transition temperatures all vary linearly with the size variance. A variance vs. size plot defines the ‘chemical window’ which enables property variations to be displayed usefully. The variance control of phase separation phenomena in manganite perovskites has also been demonstrated. In contrast, the A cation charge variance is shown to be unimportant in manganites and cuprates.</div>","PeriodicalId":10766,"journal":{"name":"Crystal Engineering","volume":"5 3","pages":"Pages 427-438"},"PeriodicalIF":0.0,"publicationDate":"2002-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1463-0184(02)00054-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77774910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 60

Nucleation and crystallization of CaCO3 in applied magnetic fields 外加磁场作用下碳酸钙的成核与结晶

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00035-7

S. Kobe , G. Dražić , A.C. Cefalas , E. Sarantopoulou , J. Stražišar

{"title":"Nucleation and crystallization of CaCO3 in applied magnetic fields","authors":"S. Kobe , G. Dražić , A.C. Cefalas , E. Sarantopoulou , J. Stražišar","doi":"10.1016/S1463-0184(02)00035-7","DOIUrl":"10.1016/S1463-0184(02)00035-7","url":null,"abstract":"<div>The formation of calcium carbonate is not only a common ionic reaction that takes place in natural processes, but also creates a problem known as scaling, which is present in our every day life and in various industrial processes and technologies. In spite of the simplicity of the reaction there is considerable variability in the properties of the solid product, such as: crystal form, particle size distribution, electro-kinetics potential, etc. The influence of the magnetic field on calcium carbonate precipitation has been known for a long time but despite a lot of effort, which has been made to explain this effect, researchers still disagree on the mechanism(s) responsible for it. The focus of our research work was to follow systematically the influence of the magnetic field on the crystal form of calcium carbonate precipitated from low concentration water solutions. By changing the strength of the field and the flow rate of the water through the system the calcite/aragonite/vaterite ratio varied. The crystal form and the particle-size distribution of the precipitated calcium carbonate were determined by using X-ray analyses and TEM. The theoretical part of the work was to study the mechanism of the influence of the magnetic field on the nucleation and further crystallization of calcium carbonate. Starting from ab initio calculations the fundamental physics knowledge was used to propose a mechanism for a better understanding of the phenomena.</div>","PeriodicalId":10766,"journal":{"name":"Crystal Engineering","volume":"5 3","pages":"Pages 243-253"},"PeriodicalIF":0.0,"publicationDate":"2002-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1463-0184(02)00035-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80838617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 75

Crystal field splitting of highly excited electronic states of the 4fn–1 5d electronic configuration of trivalent rare earth ions in wide band gap crystals 宽禁带晶体中三价稀土离子4fn - 15d电子构型高激发态的晶体场分裂

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00030-8

A.C. Cefalas , S. Kobe , Z. Kollia , E. Sarantopoulou

{"title":"Crystal field splitting of highly excited electronic states of the 4fn–1 5d electronic configuration of trivalent rare earth ions in wide band gap crystals","authors":"A.C. Cefalas , S. Kobe , Z. Kollia , E. Sarantopoulou","doi":"10.1016/S1463-0184(02)00030-8","DOIUrl":"10.1016/S1463-0184(02)00030-8","url":null,"abstract":"<div>The energy position and the spacing of the levels of the 4fn–15d electronic configuration of the trivalent rare earth ion dopands in wide band gap fluoride crystal, depend on the symmetry and the type of the host matrix. Crystal field splitting of the 4f25d electronic configuration of the Nd3+ ions in SrF2 crystals have been observed in the VUV region of the spectrum. The absorption bands were due to the interconfigurational 4f3→4f25d dipole allowed transitions between the ground state with 4f3 electronic configuration of the Nd3+ ions and the Stark components of the 4f25d electronic configuration. The VUV spectra can be interpreted by applying the crystal field model, and taking into consideration both that lanthanide contraction of the 4fn–15d electronic configuration of the rare earth ions is taking place, and that the contribution of the positively charged ions in the total electric field, is effectively decreased with increasing numbers of the electrons in the 4fn electronic configuration due to effective charge shielding.</div>","PeriodicalId":10766,"journal":{"name":"Crystal Engineering","volume":"5 3","pages":"Pages 203-208"},"PeriodicalIF":0.0,"publicationDate":"2002-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1463-0184(02)00030-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79559235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Rapid thermal annealing procedure for densification of sol-gel indium tin oxide thin films 溶胶-凝胶氧化铟锡薄膜致密化的快速热退火方法

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00028-X

K Daoudi , C.S Sandu , V.S Teodorescu , C Ghica , B Canut , M.G Blanchin , J.A Roger , M Oueslati , B Bessaïs

引用次数: 23

Effect of high temperature - pressure on SOI structure 高温高压对SOI结构的影响

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00024-2

A Misiuk , L Bryja , J Bak-Misiuk , J Ratajczak , I.V Antonova , V.P Popov

引用次数: 3

Yttrium oxide thin films: chemistry- stoichiometry-strain and microstructure 氧化钇薄膜:化学-化学计量-应变和微观结构

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00026-6

F Paumier , R.J Gaboriaud , A.R Kaul

引用次数: 20

Synthesis and characterisation of Ga-doped hexagonal BaTiO3 掺ga六方BaTiO3的合成与表征

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00055-2

A. Feteira , G.M. Keith , M.J. Rampling , C.A. Kirk , I.M. Reaney , K. Sarma , N. Mc. Alford , D.C. Sinclair

引用次数: 17

Influence of thermal treatment on the structure of Ti–Al films 热处理对Ti-Al薄膜结构的影响

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00036-9

S.E Romankov, S Suleeva, T.V Volkova, E Ermakov

{"title":"Influence of thermal treatment on the structure of Ti–Al films","authors":"S.E Romankov, S Suleeva, T.V Volkova, E Ermakov","doi":"10.1016/S1463-0184(02)00036-9","DOIUrl":"10.1016/S1463-0184(02)00036-9","url":null,"abstract":"<div>Titanium aluminides based on TiAl and Ti3Al are potential materials for high temperature aerospace application. Their low density, high temperature creep resistance and strength, high oxidation resistance, make them excellent potential engine materials. It is reasonable to develop processing strategies for protective and high temperature coatings based on them. On magnetron sputtering the Ti–48% Al alloy films, the composition of which corresponds to the target’s one, have been obtained. When annealed, the aluminium atoms have been discovered to diffuse into the substrate. The redistribution and the leveling of the films’ compositions in the volume take place. After annealing the film contains a higher titanium concentration. On sputtering the formation of the Ti3Al-based metastable phase in the films has been observed. This phase is the main one in the films and has a different morphology on different substrates. It is stable and doesn’t decompose at annealing. During annealing the new intermediate metastable phases, which are stable only within a definite temperature and concentration range, have developed. The structure, kinetics of phase transformation and evolution of the film microstructures depend on the structure and morphology of the substrate.</div>","PeriodicalId":10766,"journal":{"name":"Crystal Engineering","volume":"5 3","pages":"Pages 255-263"},"PeriodicalIF":0.0,"publicationDate":"2002-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1463-0184(02)00036-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85233711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Chemical self-diffusion in undoped ZnS and in undoped CdSe 未掺杂ZnS和未掺杂CdSe的化学自扩散

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00023-0

K. Lott, T. Nirk, O. Volobujeva

{"title":"Chemical self-diffusion in undoped ZnS and in undoped CdSe","authors":"K. Lott, T. Nirk, O. Volobujeva","doi":"10.1016/S1463-0184(02)00023-0","DOIUrl":"10.1016/S1463-0184(02)00023-0","url":null,"abstract":"<div>Chemical self-diffusion coefficients D(Δ) as a function of temperature T and metal (Zn or Cd) vapor pressure pZn or pCd has been studied in undoped ZnS and in undoped CdSe single crystals at high temperature. In the temperature range from 750 to 850 °C, D(Δ) in undoped ZnS can be described as D(Δ)=4.5×10−3 exp(−0.69 eV/kT) and in the temperature range from 1050 to 1150 °C, D(Δ) can be described as D(Δ)=1.2×10−4 exp(−0.43 eV/kT). The ZnS phase transition region is characterized by confused values of D(Δ) because of change due to mixture of phases. D(Δ) in ZnS and in CdSe is about three orders of magnitude faster than self-diffusion in these crystals in the same conditions. It was shown that the doubly ionized interstitial metal atoms are the dominanting diffusible defects in ZnS and in CdSe at high metal vapor pressure. D(Δ) is found to be almost independent on metal vapor pressure for undoped ZnS and for undoped CdSe at high pZn or pCd. In the temperature range from 565 to 700 °C, D(Δ) for CdSe can be expressed as D(Δ)=1.6×10−2 exp(−0.41 eV/kT).</div>","PeriodicalId":10766,"journal":{"name":"Crystal Engineering","volume":"5 3","pages":"Pages 147-153"},"PeriodicalIF":0.0,"publicationDate":"2002-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1463-0184(02)00023-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80571218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Phase formation and phase transition of Ln1–xCaxCoO3–δ (Ln= La, Er) applied for bifunctional air electrodes Ln1-xCaxCoO3 -δ (Ln= La, Er)在双功能空气电极中的相形成与相变

Crystal Engineering Pub Date : 2002-09-01 DOI: 10.1016/S1463-0184(02)00056-4

A. Weidenkaff , S.G. Ebbinghaus , T. Lippert , M.J. Montenegro , C. Soltmann , R. Wessicken

引用次数: 14