ISSN:
1572-8943
Keywords:
MnZn ferrite
;
TG
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Expressions for calculating the cation vacancy contents of MnZn ferrites from thermogravimetric curves are presented together with some experimental data. In a single-phase MnZn ferrite synthesized by conventional ceramic procedures, the O2 evolution accompanying ferrite formation follows the formal equation. Mn2+ σα Znσβ Fe3+ 2σ(1–γ) [V ]σ/4(1–2γ) O4 =σ'/σ Mn2+ σ(α–2ϕ) Znσβ Fe2+ 2σθ Mn3+ 2σϕ Fe3+ 2σ(1–γ–θ) [V ]σ/4(1–2γ–3ϕ) O4 +σ'φ/2O2 (g) where α and β denote the MnO and ZnO mole fractions in the primary mixture γ=α+β, θ and ϕ depend on the quantities of Fe2+ and Mn3+ formed, respectively, φ=θ–ϕ and σ'/σ is a function of the former parameters. Even though the relative amounts of Fe2+ /Fe3+ and Mn2+ /Mn3+ remain uncertain, the vacancy content [V ] of the ferrite can be determined because it depends on φ alone, which is related to the change in mass of the sample as the synthesis takes place through the equation φ=(1.5–γ) µβ /µO2 (1–m f /m i ) Here, m i and m f are the masses of the sample before and after O2 evolution, µB is the formula mass of the ferrite and µO2 is the O2 molar mass. Practically vacancy-free single-phase MnZn ferrite samples were obtained by sintering in air at 1250°C and cooling in pure N2 .
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1010138712125
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