Difference Between Stoichiometric And Nonstoichiometric Pdf
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- Non-stoichiometry and dielectric properties
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- Non-stoichiometric compound
- What is the difference between stoichiometric and nonstoichiometric compounds?
Non-stoichiometric compounds are chemical compounds , almost always solid inorganic compounds , having elemental composition whose proportions cannot be represented by a ratio of small natural numbers ; most often, in such materials, some small percentage of atoms are missing or too many atoms are packed into an otherwise perfect lattice work.
Non-stoichiometry and dielectric properties
Functional oxide materials can show a plethora of emergent complex phenomena beyond their traditional role as dielectrics, including memristive effects, catalytic activity, energy conversion, and multiferroicity. Of further interest, nano-engineered oxides offer the possibility of realizing hitherto Of further interest, nano-engineered oxides offer the possibility of realizing hitherto unobserved phenomena due to their unique responsiveness to external stimuli, multiple order-parameter couplings, and increased volume-to-surface ratio.
Consequently, oxide-based materials are becoming increasingly more important for a variety of applications including transparent electronics, optoelectronics, magnetoelectronics, photonics, spintronics, thermoelectrics, piezoelectrics, power harvesting, hydrogen production and storage, and catalysis for energy and environmental concerns.
And yet, controlled synthesis and thorough microscopic understanding of these materials remain a challenge. Stoichiometry changes are ubiquitous in oxides and can considerably affect their structural, magnetic, chemisorption and catalytic, as well as transport properties. Non-stoichiometry is indeed a pivotal facet of the functioning of oxide materials. For instance, in transition metal oxide-based heterogeneous catalysis, the presence of oxygen vacancies is sometimes necessary for any activity.
Oxygen vacancies can also significantly distort the equilibrium arrangement of atoms and modify the super-exchange interactions between neighboring magnetic ions, thus inducing spin-order transformations.
Furthermore, extrinsic vacancies enable ionic conductivity in perovskite-based solid solutions to be used in electrochemical applications, such as solid oxide fuel and electrolytic cells. In addition, the defect dynamics are strongly influenced by local electric fields, domain boundaries, surface chemical potentials, and mechanical strain.
Engineering of chemical defects in oxide compounds, therefore, emerges as a likely avenue for the design of new materials with tailored functionality. Likewise, an improved and more systematic understanding of how non-stoichiometry affects functionality will provide increasingly accurate ways of rationalizing the intriguing phenomena observed in oxide materials.
This Research Topic seeks to bring together experimental and theoretical researchers from diverse fields - such as information storage, catalysis, and energy conversion - to discuss the role of non-stoichiometry in the functional properties of oxide materials.
Keywords : Catalysis, oxide-based materials, surfaces, theory and experiments, ionic defects. Important Note : All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.
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Find out more on how to host your own Frontiers Research Topic or contribute to one as an author. Overview Articles Authors Impact. About this Research Topic Functional oxide materials can show a plethora of emergent complex phenomena beyond their traditional role as dielectrics, including memristive effects, catalytic activity, energy conversion, and multiferroicity.
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The metastable dehydration product converts to AH upon storage at the driest conditions or to HyA if exposed to moisture. HyB is a stoichiometric tetrahydrate. The loss of the water molecules causes HyB to collapse to an amorphous phase. Depending on the conditions, temperature, and a w , each of the three hydrates becomes the thermodynamically most stable form. This study demonstrates the importance of applying complementary analytical techniques and appropriate approaches for understanding the stability ranges and transition behavior between the solid forms of compounds with multiple hydrates.
The thermodynamic redox properties of ceria and ceria zirconia solid solutions are analysed with a new methodology for modelling such systems based on the statistical mechanics of lattice configurations. A dilute species model of defect clusters , obeying the law of mass action, was sufficient to describe the system over the whole range of conditions, leading to a simple analytical equation of state for the system. This offers new physical insight into the redox properties of ceria based materials, and the theoretical methods developed should also be of great interest for other materials which exhibit continuous oxygen non-stoichiometry similar to ceria, such as perovskite oxides. If you are not the author of this article and you wish to reproduce material from it in a third party non-RSC publication you must formally request permission using Copyright Clearance Center. Go to our Instructions for using Copyright Clearance Center page for details.
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What is the difference between stoichiometric and nonstoichiometric compounds?
This chapter gives a general overview of synthesis and recent development of nickel oxide as a nonstoichiometric compound. We establish the synthesis chemistry of nickel oxide as a nonstoichiometric material, and hence successively introduce definitions and classifications of nonstoichiometric compounds as well as their point defects. The samples of nonstoichiometric nickel oxide are synthesized by thermal decomposition method.
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