The importance of diagram system MnO2─NaVO3 is in obtaining a crystal phase
(chemical compounds or solid solutions). Acknowledging the fact that these compounds
have grade properties in the field of technology, it was important to study the possibi
lity of
obtaining new phases with different mole ratios, and to draw phase diagram for it,
especially the used compounds in this study have different crystal structures.
The samples were made beginning from powders of reagent grade MnO2 and NaVO3 of
5gr for each of them at following percentage mole ratios of MnO2: (10, 20, 25, 30, 33.33,
50, 66.66, 70, 71, 75, 80, 90). The mixing and grinding process was made for these
samples. Then, it made pills ellipsoidal using manually hydraulic press, and it burned into
oven at different degrees. The study was made using powder X─Rays diffraction PXRD
and different thermal analysis TG─ DTA. The results are compared with X─rays
spectrums of grade compounds and parameters of it. Then, the formation phase changes
degrees were determined. New compound was formed at ratio (MnO2)10(NaVO3)90
mole%, and crystal solid solution was formed to ratio (MnO2)25(NaVO3)75 mole%. As well
solid solution (amorphous+ new compound) was formed until mole ratio
(MnO2)75(NaVO3)25 mole%, and amorphous solid solution was formed beginning mole
ratio (MnO2)80(NaVO3)20 mole%, then the phase diagram for the studied system was
drawing.
errite (x=0.5) was prepared by a well-known conventional ceramic double sintering method (CCDS). Force constant K was calculated for tetrahedral and octahedral sites. The elastic constant C11, bulk modulus B , longitudinal and shear wave velocities w
ere calculated. Threshold frequency for electronic transition was determined using IR spectra. In addition, the drift mobility for tetrahedral and octahedral sites, as well as magnetic dipole moment changes for bond were determined. The area beneath endothermic peaks was correlated to the weight change TG%. On the other hand, the heat capacity under constant pressure CP was correlated to sample treatment temperature. It has been noticed that the CP has a critical value at 175.
