Akiyama, Toshihiko

Bando, Yoshichika

Takada, Toshio

Kyoto University Research Information Repository

Title Substitution of Manganese Ions for Iron Ions in DicalciumFerriteAuthor(s)Bando, Yoshichika; Takada, Toshio; Akiyama, ToshihikoCitationBulletin of the Institute for Chemical Research, KyotoUniversity (1972), 49(5): 342-348Issue Date1972-01-31URL http://hdl.handle.net/2433/76383RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityBull. Inst Chem. Res., Kyoto Univ., Vol. 49, No. 5, 1971       Substitution of Manganese Ions for Iron Ions                  in Dicalcium Ferrite         Yoshichika BANDO*, Toshio TAKADA*and Toshihiko  AKIYAMA**                                Received October 8, 1971      Substitution of manganese ions in 2CaO•Fe203 was studied by x-ray diffraction analysis, magnetic  and Mossbauer effect measurements. The maximum amount of manganese ions in 2CaO•Mnx Fez_ x03 was determined to be about 0.5 in x by x-ray diffraction and microstructure analyses. Neel  temperature of 2CaO•Mn0Fez_x03 (O<_x<0.5) decreased with increase of x. Lattice parameters  of 2CaO•MnxFe2_x03 varied depending on the temperature, from which it was quenched, over the  range 500° to 800°C. This phenomenon was explained on the basis of difference in the ion distri- bution in crystal lattice determined by Mossbauer effect measurement.                            INTRODUCTION   Dicalcium ferrite 2CaO•FesO3 has the orthorhombic structure, belonging to the space group Pcmn2„16, with lattice parameters: a=5.64A, b=14.68A, c=5.39A." The iron ions occupy two different sites in the crystal lattice of 2CaO•Fe2O3. One site has a tetrahedron environment, while the other an octahedron environment. It was reported that the trivalent ions, such as A13+, Ga3+ and Sc3+, were substituted for iron ions on the two lattice sites to a certain degree and the distribution of substituent ions on the two lattice sites were determined by means of the Mossbauer effect.2'    In the course of an investigation on the phase equilibria in calcium oxide-man-ganese zinc ferrite" it was found that divalent zinc ions could not replace the iron ions in 2CaO•Fe2O3 and the iron ions in 2CaO•(Mn2O3)1is(Fe2O3)si6 were replaced by zinc ions when zinc ions were less than manganese ions. For this phenomenon an expla-nation was given as follows. Since the electrical neutrality in 2CaO•Fe2O3 is main-tained, the divalent zinc ions can not replace the trivalent iron ions. When the manganese and zinc ions are substituted for the iron ions in 2CaO•Fe2O3, the condition for the electrical neutrality requires the presence of Mn" in the resulting compound where the zinc ions are divalent and the iron ions trivalent.    A clear explanation has not yet been made concerning the replacement, the valency state and the distribution of manganese ions in 2CaO•MnxFe2_xO3. The purpose of the present investigation is to elucidate these problems.    irK*A j, mfijA : Laboratory of Solid State Chemistry, Institute for Chemical Research, Kyoto University, Uji, Kyoto. ** : Department of Materials Science, Himeji Institute of Technology, Shosha, Himeji-shi. (342)               Substitution of Manganese Ions for Iron  Ions in Dicalcivan Ferrite                      EXPERIMENTALS AND RESULTS 1. Preparation of Sample.     Commercial chemicals of highest purity were used as starting materials. CaCO3, MnCO3 and a-FeOOII were mixed in stainless steel mills with a methanol medium and dried. The mixtures were compacted and calcined at 1000°C for 1 hr. The calcined compacts were then crushed in an agate mortar. The powder was pressed at 1 ton per sq. cm, heated at 1400°C for 25 hr and further at 1000°C for 1 hr and then quenched to room temperature in air. The sintered specimens thus obtained were ground to fine powder for x-ray analysis, magnetic and Mossbauer effect measure-ment. 2. X-ray Analysis     X-ray examinations were made using a Nippondenshi diffractometer with an iron target. Qualitative identification was made by scanning from 10 to 85 degrees two theta. X-ray patterns of 2CaO•MnxFe2_x03(x<0.5) were closely resemble to that of 2CaO•Fe203, showing these specimens to be a single phase. However, dif-fraction peaks of CaMnO3 phase containing iron ions were observed for the specimens with the compositions of x>0.7. The lattice parameters of the series of 2CaO•Mn3 5.6 S. 5.58 - •a 5.56-  5.54- • —5 .52-                  0 c15.0o------------0 b• 14.9-•b                                            •            14.8- •        a) • .`_ 14.7-         5.44 -            5.4 - 5.40-            5.38- 5.36 -            0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 x               Fig. 1. Variation of latticeconstants with x in 2CaO•MnxFe2_xO3. ( 343 )                           Y. BANDO, T. TAKADA and  T. AKIYAMA Fe2O3_x were calculated using the (200), (080) and (202) diffractions for the specimens which were annealed at 1000°C for 3 hr and quenched to room temper-ature in air. The results are shown in Fig. 1. It can be seen that the manganese substitution for iron ion in 2CaO•FezO3 leads to contraction of lattice parameter a and c and expansion of b. A change in slope is found at x=0.5. It can be considered that the maximum amount of manganese ions which enter the 2CaO•Fe3O3 lattice structure is nearly equal to x=0.5. 3. Microscopic Examination    Polished sections of the sintered specimens were examined with an Olympus PEM microscope after etched with an aqueous solution of 250/ HC1. Microstructures of the specimens are shown in Fig. 2. In the specimens x<0.5 only a single phase pre-cipitated whereas in those x>0.5 a second phase co-precipitated. The latter phase seems to be CaMnO3 considering from the x-ray data. 4. Magnetic Measurement     Magnetic susceptibility was measured with a Shimazu torsion magnetometer in the range from room temperature to 873°K. The dicalcium ferrite and the substi-            0, ... -it. 4 • -.., ...„t, . .,,:...._, Aillk Alp    .• 41),. ,. . lik,...0 •. • ,.                                               . - I* ''*4         -,~        • i 2O1`^-4    (a)(b)  '? t V4,*~          1^_1 '#.                   „.4„,                                ,... ., ,   ...„ . : ..v ..,:- . • . ,. I* tt ,I, ',±. 4 (c)(d)              Fig. 2. Microstructures of 2Ca0•Mn,Fez_x03 quenched from 1300°C.                 (a) x=0, (b) x=0.4, (c) x=0.55, (d) x=0.6( 344 )             Substitution of Manganese Ions for Iron Ions in Dicalcium Ferrite   '18 _0(10-6  e.m.u./g) •  =17-•                         •      •.4--716 - •                      (a) a• ' v15_•S.  ~ 14— •  (n1 3 -12-•   c11 - ° ° °O o 00°'•. •ag o   10_ 00°°°   9- 1 1 1 I I I I      300 400 500 600 700 800 900              Temperature (°K )  -'' 20-(x10-6e.m.u./g ) _19-(b)    18-   a17 -®'••• •.•••. U• I^1• • (n+6•        —0 °pO °°°° o o ° °•°•°.O     150 0 0 O---...o •O                                                                          o. °. U14 _  c13-  ~12-  11 - 1 I1 1 1I 1      300 400 500 600 700 800 900              Temperature (°K )                 Fig. 3. Temperature dependence of magnetic susceptibilities.                       (a) 2CaO•Fe203, (b) 2CaO•Mno.3Fej.703 tuted compounds were antiferromagnetic and had a spontaneous magnetic moment below Neel temperature when the specimens were cooled down from above Neel temperature in magnetic field (Fig. 3.) As shown in Table 1, Neel temperature ( 345 )                           Y. BANDO, T.  TAKADA and T. AKIYAMA                      Table 1. Neel Temperatures for 2Ca0•MnxFez_x03 Neel temperature                                            (°K)0730       0.1628       0.2593       0.3539 decreased with increase of an amount of manganese ions in the solid solution. This phenomenon can be considered to be caused by the replacement of the iron ions in the crystal lattice of 2CaO•Fe2O3 with the manganese ions. 5. Variation of Lattice Parameters of Mn Substituted Dicalcium Ferrite    with Heat Treatment.    The powders of 2CaO•Mno.3Fe1.7O3 were heated previously at 1000°C for 1 hr, slowly cooled to desired temperatures above 500°C, kept at the temperatures for 1 5.57- 5.56- -cc 5.55-a 554-           14.a0- u 14.85-            a, 14.80-             ra        J             5.41-                                  c              5.40-               5.39-             500 600 700 800 900 1000               Annealing Temperature (CC)      Fig. 4. Variation of lattice constants of 2CaO•Mn0.3Fe1.703 with annealing temperature. ( 346 )           Substitution of Manganese Ions for Iron Ions in Dicalcium Ferrite Counts (  x105  ) 2.75'                                                                                                                                                                                     • 2.70• .••                                                                       • (a)•                                                                                                                                                                                       •                                                                                                                                                                                                               • 2.65 1B 1A 2A2B 3A3B 4A 4B 5A 5B 6A6B 1 1 I i I 1 1 1 I. . I                                                                       • 480••••'.'c:'14,, •••::%:•;:; . 4.75 }:• • 4.70 •                                                                                                                                                                                                          • 4.65• • (b) 4.L.• •                                                                                                                                                          • 4.55•                                               • 3.75 • 3.70(c) 3.65   -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 Velocity (mm/sec )          Fig. 5. Mossbauer spectra of (a) 2CaO•Fe2O3i (b) 2CaO•Mno,3Fej.703             quenched from 1200°C and (c) 2CaO•Nno,3Fei•703 annealed at 500°C             for 20 hr. ( 347 )                           Y. BANDO, T. TAKADA and T. AKIYAMA to 25 hr in air to obtain equilibrium state, and quenched in water. Variation of lattice parameters of the specimens with annealing temperature is shown in Fig. 4. When the annealing temperature was above 800°C, there was little variation in lattice parameters. In the range lower than 800°C, however, the lattice parameters a and b decreased and c increased with decreasing annealing temperature. The similar feature was observed for the other specimens having a different amount of manganese ions.    The variation of lattice parameters is considered to be caused by the alternation of the valency state and the ion distribution of the manganese ions. This was con-firmed by the follwoing  Mossbauer effect measurement. 6. Mossbauer Effect Measurement Mossbauer effect measurements at liquid nitrogen temperature were carried out using an apparatus consisting of Erlon's driving unit and Nothern Scientific Co's 1000 channel pulse height analyzer. Calibration of the velocity scale was made using pure Fe and a-Fe203 as standard absorbers. Figure 5(a) shows the MOssbauer spectra of 2Ca0•Fe203. The spectrum consists of two six line spectra of equal intensity (the larger internal field corresponding to the octahedral sites). The two spectra are well-separated and the magnetic splitting is different. The spectrum of 2CaO•Mno.3Fei.703 heated at 1200°C is shown in Fig. 5(b). This figure indicates a similar splitting to that presented in Fig. 5(a). However, the intensities of two spectra representing the two sites are very different and the intensity ratio is 0.7. Therefore, it is clear that all of the manganese ions locate at the octahedral sites. Figure 5(c) shows the spectrum of the specimens annealed at 500°C for 24 hr. The spectrum consists of two six line spectra of equal intensity. In this case, manganese ions locate equally at octahedral and tetrahedral sites. This fact shows that the variation of lattice constants with the quenching temperature is mainly caused by that of ion distribution. This variation would lead the crystal toward a more ordered and more stable form at higher temper-ature.    It may be necessary to consider change of valency of manganese ions with heat treatment. However, the valency of manganese ions could not be directly confirmed by means of chemical analysis and chemical shift measurement of fluorescent x-ray. The details of the valency state will be published elsewhere in the near future.                        ACKNOWLEDGMENTS    The authors wish to thank Drs. T. Shinjo and M. Takano for Mossbauer effect measurements and helpful discussions.                             REFERENCES (1) E. F. Bertaut, P. Blum, and A. Sagnieres, Acta Crys., 12, 149 (1959). (2) R. W. Grant, H. Wiedersich, S. Geller, U. Gonser, and G. P. Espinosa, J. Appi. Phys., 38, 1455     (1967). (3) Y. Bando, T. Kato, Y. Ikeda, and T. Takada, Bull. Inst. Chem. Res., Kyoto Univ., 46, 289 (1968). ( 348 )

Substitution of Manganese Ions for Iron Ions in Dicalcium Ferrite

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Substitution of Manganese Ions for Iron Ions in Dicalcium Ferrite

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