Шілде–тамыз–қыркүйек 30 қыркүйек 2014 ж. 1996 жылдан бастап шығады Жылына 4 рет шығады
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- Бұл бет үшін навигация:
- The experimental values of the heat capacity of compounds LaM II 3 Fe 5 O 12
- Equations of the temperature dependence of the specific heats of ferrites LaM II 3 Fe 5 O
- Thermodynamic functions LaM II 3 Fe 5 O 12 (M
- ), Ф хх ( Т ), Н 0 ( Т ) – Н 0
- Термодинамические исследования ферритов состава LaM II 3 Fe 5 O
- Construction of phase diagram in systems Na
5 O 12 (M II — Mg, Ca, Sr) New ferrites LaM II 3
5 O 12 (M II — Mg, Ca, Sr) were obtained by high-temperature synthesis on ceramic tech- nology. By powder X-ray diffraction established that compounds crystallize in the tetragonal singonia, the pa- rameters of its crystal lattices are determined. The heat capacity of ferrites has been defined by dynamic calo- rimetric method at 298.15–673 K and detected the presence of phase transitions of type II. The equations de- scribing the dependence in the range 298.15–673 K are derived taking into account the phase transitions. Key words: heat capacity, temperature dependence of the heat capacity, phase transitions, ferrites, perovskite.
Oxides of variable valence metals with the perovskite structure are a class of materials that exhibit a number of interesting and important effects for practical applications: metal-insulator transitions, magnetic ordering of different nature (ferromagnetism and antiferromagnetism), superconductivity. Therefore, they are of interest among scientists around the world, carrying out the theoretical researches aimed to understanding the nature of these physical effects, and applied studies in the field of technology of perovskite oxides. It is possible to create variety of devices based on them due to the electronic properties of oxides. This direction of study has been called oxide electronics [1]. The aim of this work is calorimetric study of ferrites’ heat capacity LaM II 3
5 O 12 (M II — Mg, Ca, Sr) in the range of temperature 298.15–673 K. New ferrites synthesized by solid-phase reaction at high temperature at presence of oxides La 2 O
, Fe 2 O 3 , magnesium carbonate, calcium and strontium. There were established by the method of radiography that ferrites crystallize in the dimetric system with the next lattice parameters: LaMg II 3
5 O 12 ; a = 11,105 Å; с = 17,1 Å; V o = 2109,3 Å 3 ; 263,66 Å 3 ; 8;
roentgen = 4,3 g/cm 3 ; picn
= 4,45 ± 0,09 g/cm 3 , LaCa II 3 Fe 5 O 12 ; a = 11,005 Å; с = 16,91 Å; 2047,89 Å 3 ; 255,99 Å 3 ; 8; roentgen = 4,74 g/cm 3 ; picn
= 4,82 ± 0,04 g/cm 3 , LaSr II 3 Fe 5 O 12 ; a = 11,1 Å; с = 16,98 Å; 2076,57 Å 3 ; 259,57 Å 3 ; 8;
roentgen = 5,58 g/cm 3 ; picn
= 5,61 ± 0,07 g/cm 3 . Experimental part Isobaric heat capacity of ferrites was investigated in the temperature range 298.15–673 K on ITS-400 calorimeter. Duration of the measurements over the all temperature range with the processing of the experi- mental data was not more than 2.5 hours. Maximum permissible error of the instrument on passport data was ±10.0 %. Calibration of the device was carried out by determining the thermal conductivity of К
heat meter [2, 3]. Several experiments carried out with a copper pattern and an empty ampoule for this purpose. Lag time to achieve the desired temperature was recorded using microvoltampermeter F136 and digital stopwatch with a step of 25 K. The heat capacities of samples were also measured at 25 K. At each temperature five parallel experiments were carried out, the results were averaged due to method [4], then were calculated ran- dom components of error (Δ) for C p(sp)
(specific) and С p (mol) of the specific heats values. By method of powder radiography there were established that compounds crystallize in the dimetric system, the parameters of their crystal lattices are determined. By method of dynamic calorimeter at 298.15– 673 K the heat capacity of ferrites has been defined, wherein the presence of phase transitions of type II re- vealed. The equations describing the dependence at 298.15–673 K temperature were derived taking into ac- count the phase transitions. There are results of the calorimetric studies in Table 1 below.
E.S.Musstafin, R.Z.Kasenov et al. 22
Вестник Карагандинского университета T a b l e 1 The experimental values of the heat capacity of compounds LaM II 3 Fe 5 O 12 (M II — Mg, Ca, Sr) T , K
C p C p
T , K
C p C p
LaMg 3 Fe 5 O 12 298 0,73±0,01 495,69±4,88 498 0,60±0,03 411,09±21,60 323 0,94±0,06 645,37±38,26 523 0,58±0,04 396,44±25,64 348 0,87±0,05 594,43±36,85 548 0,51±0,03 350,16±17,72 373 0,79±0,05 539,65±34,37 573 0,42±0,02 288,60±14,71 398 0,69±0,14 471,78±96,09 598 0,35±0,02 242,05±14,09 423 0,61±0,04 419,21±24,19 623 0,34±0,03 234,12±17,80 448 0,54±0,03 368,02±21,88 648 0,35±0,02 240,96±14,51 473 0,55±0,03 376,73±20,75 673 0,40±0,03 271,60±17,38 LaCa
3 Fe 5 O 12
298 0,39±0,30 285,62±218,95 498 0,56±0,06 407,69±45,08 323 0,87±0,05 636,52±34,21 523 0,60±0,04 439,24±30,84 348 0,82±0,13 596,31±94,01 548 0,70±0,05 510,10±38,83 373 0,73±0,30 534,79±220,48 573 0,53±0,05 387,46±34,97 398 0,66±0,03 479,87±21,46 598 0,37±0,03 270,55±21,97 423 0,57±0,03 416,94±25,18 623 0,28±0,05 207,94±35,37 448 0,53±0,65 385,18±473,80 648 0,24±0,30 178,86±220,92 473 0,49±0,04 359,00±30,53 673 0,22±0,02 158,54±12,55 LaSr 3
5 O 12 298 0,70±0,00 610,86±3,04 498 0,51±0,02 444,51±17,17 323 0,88±0,05 769,09±47,92 523 0,47±0,02 409,61±18,10 348 0,83±0,05 724,18±45,57 548 0,42±0,12 370,43±103,96 373 0,70±0,04 613,67±31,84 573 0,38±0,02 330,44±13,55 398 0,61±0,03 535,80±22,22 598 0,35±0,02 304,52±13,18 423 0,55±0,04 480,56±33,48 623 0,35±0,02 304,89±17,56 448 0,49±0,03 426,17±25,00 648 0,37±0,16 322,95±143,05 473 0,43±0,03 375,97±24,30 673 0,40±0,18 350,93±159,62
The equation of temperatures dependence of the heat capacity is derived (Table 2). The dependence heat capacity on temperature is depicted taking into account the experimental data on C p °(T) (Fig. 1–3). T a b l e 2 Equations of the temperature dependence of the specific heats of ferrites LaM II 3 Fe 5 O 12 (M II — Mg, Ca, Sr) Compounds Coefficients of the equation
0 p = a +
+
c
–2 , J/(mol·К) T , K
a b c 10
–5
LaMg 3 Fe 5 O 12
–1500,24 6,45 64,0877 298,15–323,0 1059,98 –1,70 140,6381 323,0–448,0 –4617,36 7,34 3407,81 448,0–498,0 7062,98 –8,89 –5517,27 498,0–573,0 –6783,18 7,49 9136,514 573,0–673,0 LaCa
3 Fe 5 O 12
–3262,26 12,70 –212,122 298,15–323,0 718,25 –1,00 250,4178 323,0–473,0 –933,34 2,46 291,1446 473,0–548,0 –7580,43 7,67 11675,89 548,0–673,0 LaSr
3 Fe 5 O 12
17089,38 –33,06 –5886,57 298,15–348 46,12 –0,13 876,2147 348,0–473 20615,07 –26,82 –16894,6 473,0–523,0 –4252,29 5,01 5590,562 523,0–673,0
Серия «Химия». № 3(75)/2014 Figure 1. Dependence of the he LaCa 3
5 O 12 on tempera Figure 3. Depe Data from Table 1 shows that t racy of the calorimeter. It is found o the heat capacity C p °~ƒ(T). This fac transitions may be caused by cation advent of the Curie and Neel [5], etc It is known that in compounds anomaly connected with the Schottk Since the possibilities of calori ied ferrites directly from the experim increments [6]. Also coefficients o ble 2):
Ф Thermod
eat capacity ature
Figure 2. Dependence of LaMg
3 Fe 5 O 12 on t endence of the heat capacity LaSr 3 Fe
O 12 on temperatu the error of measurement of the heat capacity fit w out that a number of ferrites has a sharp jumps in ct occurs probably due to the presence of phase t nic redistributions, changes of the coefficients of c. containing paramagnetic transition metal ions, o ky effect. imeter IT-400 do not allow to calculate the stand mental data on C p °(T), it was estimated using th f the temperature dependence of the heat capac H 0 (T) – H 0 (298.15) = 0 298.15
T p C dT ; S 0 (T) = S 0 (298.17) + 298.15
; Ф хх (Т) = S 0 (T) – 0 0 ( ) (298.15) H T H T . dynamic study of ferrites … 23
f the heat capacity temperature ure within permissible accu- the dependence curve of transitions type-II. These f thermal expansion, the often occur heat capacity dard entropy of the stud- e method of ion entropy city are determined (Ta- (1)
(2) (3)
E.S.Musstafin, R.Z.Kasenov et al. 24
Вестник Карагандинского университета In continuation of our studies there were calculated temperature dependence of thermodynamic func- tions (S°(T), H°(T) – H°(298,15)) using the ratios 1, 2, 3 and the experimental data of C p °~ƒ(T) was applied. S°(T), H°(T) – H°(298,15) and Ф хх (T) ferrites (Table 3). T a b l e 3
, К
С 0 р ( Т )
0 (
) Ф хх (
)
0 ( Т ) –
Н 0 (298,15) LaMg 3 Fe 5 O 12 298 495,7±4,9 365,3 ± 11 365,3 ± 11 – 323
645,4±38,3 410,9 ± 41 367,0 ± 37 14172,4 ± 891 348 594,4±36,9 456,7 ± 46 371,8 ± 37 29533,0 ± 1858 373
539,7±34,4 495,2 ± 50 378,9 ± 38 43411,2 ± 2731 398 471,8±96,1 527,6 ± 53 387,2 ± 39 55886,0 ± 3515 423
419,2±24,2 554,8 ± 55 396,3 ± 40 67017,8 ± 4215 448 368,0±21,9 577,4 ± 58 405,8 ± 41 76853,3 ± 4834 473
376,7±20,7 597,5 ± 60 415,4 ± 42 86103,4 ± 5416 498 411,1±21,6 617,7 ± 62 425,1 ± 43 95903,2 ± 6032 523
396,4±25,6 637,6 ± 64 434,8 ± 43 106060,9 ± 6671 548 350,2±17,7 655,2 ± 66 444,4 ± 44 115494,2 ± 7265 573
288,6±14,7 669,6 ± 67 454,0 ± 45 123570,8 ± 7773 598 242,1±14,1 681,0 ± 68 463,2 ± 46 130216,6 ± 8191 623
234,1±17,80 690,8 ± 69 472,2 ± 47 136190,7 ± 8566 648 240,9±14,5 700,1 ± 70 480,8 ± 48 142112,4 ± 8939 673
271,6±17,4 709,8 ± 71 489,1 ± 49 148508,9 ± 9341 LaCa 3
5 O 12 298,15 285,62±21,9 411,9 ± 12 411,8 ± 12 – 323
636,52±34,2 448,7 ± 45 413,1 ± 41 11517,8 ± 724 348 596,31±94,0 494,0 ± 49 417,3 ± 42 26688,4 ± 1679 373
534,79±22,5 532,3 ± 53 423,8 ± 42 40489,9 ± 2547 398 479,87±21,5 564,9 ± 56 431,6 ± 43 53062,8 ± 3338 423
416,94±25,2 592,9 ± 59 440,4 ± 44 64514,7 ± 4058 448 385,18±47,8 616,8 ± 62 449,5 ± 45 74928,9 ± 4713 473
359,00±30,5 637,3 ± 64 458,9 ± 46 84371,4 ± 5307 498 407,69±45,1 657,0 ± 66 468,4 ± 47 93950,9 ± 5910 523
439,24±30,8 678,2 ± 68 477,9 ± 48 104770,7 ± 6590 548 510,10±38,8 700,8 ± 70 487,6 ± 49 116871,2 ± 7351 573
387,46±34,9 720,3 ± 72 497,3 ± 50 127779,4 ± 8037 598 270,55±21,9 733,9 ± 73 506,9 ± 51 135708,0 ± 8536 623
207,94±35,4 743,5 ± 74 516,2 ± 52 141592,7 ± 8906 648 178,86±22,9 750,8 ± 75 525,2 ± 53 146224,9 ± 9198 673
158,54±12,6 756,9 ± 76 533,7 ± 53 150278,2 ± 9453 LaSr 3
5 O 12 298,15 285,6±21,95 444,8 ± 13 444,8 ± 44 – 323
636,5±34,21 501,5 ± 50 446,9 ± 45 17632,9 ± 1109 348 596,3±24,01 558,3 ± 56 452,9 ± 45 36662,8 ± 2306 373
534,8±22,48 605,1 ± 61 461,6 ± 46 53514,1 ± 3366 398 479,9±21,46 643,1 ± 64 471,9 ± 47 68163,7 ± 4287 423
416,9±25,18 674,4 ± 67 482,9 ± 48 80987,5 ± 5094 448 385,2±47,80 700,4 ± 70 494,4 ± 49 92277,6 ± 5804 473
359,0±30,53 722,1 ± 72 505,9 ± 51 102264,0 ± 6432 498 407,7±40,08 743,7 ± 74 517,2 ± 52 112757,9 ± 7092 523
439,2±30,84 765,0 ± 76 528,6 ± 53 123628,9 ± 7776 548 510,1±38,83 782,7 ± 78 539,8 ± 54 133102,5 ± 8372 573
387,5±34,97 797,6 ± 80 550,7 ± 55 141449,3 ± 8897 598 270,6±21,97 810,8 ± 81 561,3 ± 56 149203,2 ± 9385 623
207,9±35,37 823,3 ± 82 571,6 ± 57 156812,2 ± 9863 648 178,9±22,92 835,6 ± 84 581,5 ± 58 164655,1 ± 10357 673
158,5±12,55 848,3 ± 85 591,2 ± 59 173054,5 ± 10885
Thermodynamic study of ferrites … Серия «Химия». № 3(75)/2014 25 Errors of the temperature dependence of the thermodynamic functions were calculated based on an av- erage error of the heat capacity and entropy calculation accuracy (3 %). Conclusion 1. Isobaric heat capacity of iron LaM II 3
5 O 12 (M II — Mg, Ca, Sr) was measured at temperature 298.15–673 K for the first time. 2. It is revealed a sharp jumps in the heat capacity connected with the presence of phase transitions of type II. 3. Equations of the temperature dependence of the heat capacity have been calculated taking into ac- count the temperatures of phase transitions type II. 4. The functions S°(T), H°(T) – H°(298,15) and Ф хх (T) were calculated in the certain temperature inter- val.
References 1 Tretyakov Y.D., Lepis W. Chemistry and technology of solid-state materials. — Moscow: Moscow State University Press, 1985. — P. 256. 2 Platunov E.S., Burawoy S.E., Kurepin V.V., Petrov G.S. Thermophysical measurements and instruments. — Moscow: Mashinostroenie, 1986. — P. 256. 3 Technical description and operating instructions ITS-400. — Aktobe: Aktobe plant «Etalon», 1986. — P. 48. 4 Spiridonov V.P., Lopatkin L.V. Mathematical processing of experimental data. — Moscow: Moscow State University Press, 1970. — P. 221. 5 Reznitskii L.A. Calorimetry solid. — Moscow: Moscow State University, 1981. — 184 p. 6 Kumok V.N. Problem of matching methods to assess the thermodynamic characteristics // Direct and inverse problems of chemical thermodynamics. — Novosibirsk: Nauka, 1987. — P. 108–123.
Е.С.Мұстафин, Р.З.Қасенов, А.М.Пудов, С.А.Блялов, А.А.Мұратбекова LaM II 3 Fe 5 O 12 (M II — Mg, Ca, Sr) құрамды ферриттердің термодинамикалық зерттеулері Мақалада керамикалық технология əдісі бойынша жоғары температуралық синтезбен жаңа ферриттер алынған LaM II 3 Fe 5 O 12 (M
II — Mg, Ca, Sr). Қосылыстардың тетрагоналды сингония бойынша кристал- данатыны ұнтақты рентгенография əдісі арқылы дəлелденді, олардың кристалл торларының параметрлері анықталды. Ферриттердің жылусыйымдылықтары 298,15–673 К температура аралығында динамикалық калориметрия əдісімен зерттелді жəне бұл жағдайда 2-ші реттік фазалық ауысу орын алатыны көрсетілді. Фазалық ауысуларды ескере отырып, 298,15–673 К температура аралығында тəуелділікті сипаттайтын теңдеулер қорытылып шығарылды.
Е.С.Мустафин, Р.З.Касенов, А.М.Пудов, С.А.Блялов, А.А.Муратбекова Термодинамические исследования ферритов состава LaM II 3 Fe 5 O 12 (M II — Mg, Ca, Sr) В статье высокотемпературным синтезом по керамической технологии получены новые ферриты LaM II
Fe 5 O 12 (M
II — Mg, Ca, Sr). Методом порошковой рентгенографии установлено, что соединения кристаллизуются в тетрагональной сингонии, определены параметры их кристаллических решеток. Методом динамической калориметрии в интервале 298,15–673 К определены теплоемкости ферритов, при этом выявлено наличие фазовых переходов II рода. С учетом фазовых переходов выведены урав- нения, описывающие зависимость, в интервале 298,15–673 К. 26 Вестник Карагандинского университета UDC 546.06 Sh.K.Amerkhanova 1 , V.D.Alexandrov 2 , А.Yu.Sobolev 2
E.A.Buketov Karaganda State University; 2 Donbas National Academy of Civil Engineering and Architecture, Makeyevka, Ukraine (E-mail: amerkhanova_sh@mail.ru) Construction of phase diagram in systems Na жүктеу/скачать 4,74 Mb. Достарыңызбен бөлісу:
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