摘要:
Disclosed is a method for preparing heteroepitaxial thin films which are free of island structures which have a bad influence on the photoelectric properties and interfacial reactivity of the thin films. These heteroepitaxial thin films are deposited on grooved or curved surfaces of substrates. The use of grooved substrates relieves the coherent elastic strain from the thin films, thereby inhibiting the surface roughening and the island structure formation in the heteroepitaxial thin films. The method can be applied to all of the thin films that show island structures, including GaAs/Si and SiGe/Si typically used in semiconductor devices and various electronic parts, enabling the thin films to be flatly deposited at a significant thickness on various substrates without additionally processing.
摘要:
A method for making a BaTiO3-based dielectric having a high dielectric constant and a low dielectric loss wherein, a BaTiO3-based body is subjected to a pre-heat treatment in a hydrogen (H2) atmosphere or a reducing atmosphere containing mixed gas of hydrogen and nitrogen in a ratio of hydrogen:nitrogen=5 to 100%:0 to 95% prior to a sintering process in the manufacture of dielectrics, in order to obtain a reduced average grain size of BaTiO3. By virtue of the reducing average grain size of BaTiO3, a BaTiO3-based dielectric having a high dielectric constant and a low dielectric loss is obtained. This method provides an advantage in that it is possible to make a BaTiO3-based dielectric having a very small average grain size while having a high relative density in accordance with a simple heat treatment conducted for pure BaTiO3 or even for BaTiO3 added with an additive in a reducing atmosphere at a temperature less than a liquid phase forming temperature, prior to a sintering process for sintering the BaTiO3.
摘要:
Provided are lithium transition metal phosphates where the cation anti-site defects between lithium and transition metals in a lithium transition metal phosphate with a cation well-ordered olivine structure are arranged only in a 1D crystal direction, and a method of preparing the same. The method comprises adding any one selected from the group consisting of an alkali element and an element that has a valence of 5+ or any combination thereof to a solid salt comprising lithium, transition metals, and phosphorus as a starting material to produce a first intermediate material; subjecting the first intermediate to a first heat treatment at a temperature of approximately 250° C. to approximately 400° C. to produce a second amorphous material; and cooling the second intermediate material to room temperature, followed by a second heat treatment at a temperature of approximately 400° C. to approximately 800° C. to produce a final material in which the cation-distribution defect is locally clustered and the distribution has a 1D-oriented arrangement parallel to any one axis direction in the crystal.
摘要:
A process for preparing a nanoparticle powder of a lithium transition metal phosphate includes mixing lithium, a transition metal and a phosphorus-containing salt as starting materials, adding an additive to the starting materials in an amount of greater than 0 at % and less than 10 at % to obtain a mixed raw material powder, subjecting the mixed powder to a first heat treatment at a temperature of 250° C. to 400° C. under a gas atmosphere for 2 to 10 hours; and subjecting the first heat-treated product to a second heat treatment at a temperature of 400° C. to 700° C. for 2 to 24 hours to uniformly form crystalline nuclei so as to induce growth of nanocrystalline particles. The additive may be any one element selected from the group consisting of sodium (Na), potassium (K), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd) and erbium (Er).
摘要:
Provided is a process for preparing a nanoparticle powder of lithium transition metal phosphate, involving synthesis of lithium transition metal phosphate (LiMPO4) (M=Fe, Mn, Co, Ni, Ti, Cu or any combination thereof) into a nanoparticle powder having a particle size of less than 100 nm to thereby significantly reduce a diffusion distance of lithium ions within particles, which consequently results in full exploitation of a capacity of an electrode material corresponding up to a theoretical capacity thereof and formation of nanoparticles having a high electrical conductivity within a short period of time, and which is also capable of achieving efficient industrial-scale production of a desired compound via a heat treatment at a low temperature of less than 600° C. for a short period of time of less than 4 hours while overcoming a shortcoming of a low electrical conductivity, using solid raw materials. The process comprises mixing lithium, a transition metal and a phosphorus-containing salt as starting materials, with addition of any one element selected from the group consisting of sodium (Na), potassium (K), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd) and erbium (Er) in an amount of less than 10 at % to thereby inhibit nucleation in a first heat treatment, subjecting the reactants to first heat treatment at a temperature of 250° C. to 400° C. for 2 to 10 hours, and subjecting the first heat-treated materials to a second heat treatment at a temperature of 400° C. to 700° C. for 2 to 24 hours to uniformly form crystalline nuclei to induce growth of nanocrystalline particles.