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A Study Of The Solid Regions In The System Zr-Te, Frances Dolores Jenkins
A Study Of The Solid Regions In The System Zr-Te, Frances Dolores Jenkins
Doctoral Dissertations
"Relative intensity measurements of X-ray powder diffraction lines were made of compositions in the region ZrTe₀.₅ to ZrTe₂.₀, fired between 600º and 817ºC in evacuated sealed tubes. The experimental relative intensities of samples between ZrTe and ZrTe₂ were compared with values calculated for several theoretical models with different Zr vacancy ordering schemes and Te vacancy concentrations. The most probable structural model for compositions in the range ZrTe to ZrTe₁.₅ is one in which the number of Zr vacancies located at z = 0 ranges from 0% to 30%, with the concentration of Te vacancies ranging from 0 to 35%. A …
Synthesis And Properties Of Cadmium Manganese Ferrites, B. W. Jong
Synthesis And Properties Of Cadmium Manganese Ferrites, B. W. Jong
Doctoral Dissertations
"The formation sequence of (Cd,Mn,Fe) (Mn,Fe)₂O₄ from the individual oxides,x CdO + (1-x) MnCO₃ + α-Fe₂O₃,was found by X-Ray diffraction. Cd(Mn,Fe)₂O₄ was formed completely from CdO·Fe₂O₃ and CdO·Fe₂O₄ at 900°C and reacted with MnFe₂O₄ for 0 < x < 0.5 and with α-Fe₂O₃ for 0.5 < x < 1.0 to form a single phase of (Cd,Mn,Fe) (Mn,Fe)₂O₄ at 1150°C. This is the first time that the details involved in the formation sequence of CdMn-ferrite have been shown. A mixture of 0.5 CdO + 0.5 MnCO₃ + α-Fe₂O₃ was calcined at 900°C for 2 hrs forming Cd(Mn,Fe)₂O₄ with no Cd present in the other phases. Sintering was accomplished at 1150°C for 30 minutes forming a single phase of Cd₀.₅Mn₀.₅Fe₂O₄ with a bulk sintered density of 98-99% of the X-Ray density. The rate of changing density followed the relationship, p = K ln t + c, at temperatures between 1050°C and 1300°C. Magnetic properties of CdₓMn₁₋ₓFe₂O₄ were affected by composition x. A relationship, B = gx + h, was found between maximum magnetic flux density B and composition x at room temperature for 0 <̲ x <̲ 0.3. This was rationalized by a modification of Néel's theory. The maximum magnetic flux density decreased with increasing cadmium concentration for 0.3 < x <̲ 0.5. This decrease was attributed to the changing direction of the magnetic moment in the octahedral site sub-lattice according to the superexchange theory. No magnetic properties were observed due to the formation of a compensated antiferromagnetic phase for 0.5 < x <̲ 1.0. Maximum magnetic flux density increased with bulk density, while the coercive force decreased with the grain growth and the initial permeability increased with the bulk density and grain size. A stator core used for a-c electric motor application was formed by pre-sintering at 900⁰C for 2 hrs. Slots were then sawed with a tungsten carbide blade and final sintering was accomplished at 1150⁰C for 1 hr"--Abstract, pages iii-iv.