Magnesium diniobate

Melting point / freezing point

Link to relevant study record(s)

Reference

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-03-24 to 2016-04-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

Version / remarks:

1995

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.1 (Melting / Freezing Temperature)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2013-03-22

Type of method:

differential scanning calorimetry

Decomposition:

no

Sublimation:

no

Remarks on result:

other: no melting point up to 650 °C

Open aluminium crucibles

During the heating phase, thermal effects (melting or boiling) were not observed in the temperature range of 25 – 500 °C.

Results of the DSC-measurements (open aluminium crucibles)

Sample weight [mg]	Onset of Effect [°C]	Range of effect [°C]	Weight loss [mg]	Atmospheric pressure [hPa]
10.83	---	---	0.00	1012
13.13	---	---	0.00	1012

Glass crucible (open and closed)

During the heating phase, exothermic effects were observed in the temperature ranges of 470 – 620 °C and 510 – 610 °C with an energy of -50 J/g and -120 J/g, respectively. Weight loss and change in appearance of the  test item were not observed.

Results of the DSC-measurements (glass crucibles)

Sample weight [mg]	Onset of Effect [°C]	Range of effect [°C]	Energy [J/g]	Atmospheric pressure [hPa]	Remark
9.02	---	470 – 620	-120	998.1	open glass crucible
8.83	---	510 – 610	-50	1008.2	closed glass crucible

The test item magnesium diniobate did not melt or boil up to 650 °C, however, an exothermic peak was observed starting at 470 °C. Heat flows out of a sample as a result of an exothermic process, including (re)crystallization and oxidation. Thus, melting and boiling can be excluded as these are endothermic reactions. For the test item Magnesium diniobate (MgNb₂O₅), it is most likely that the exothermic peak indicates a change in the crystal structure (e.g. metastable to stable phase). Other exothermic reactions may be excluded for the following reasons:

- Oxidation is not possible; all elements are in the highest possible oxidation state,

- Reaction not likely at this temperature range due to the lack of reactants,

- Decomposition is not likely since a split-off of oxygen is highly unlikely based on the expected strong oxidation properties of oxygen (MgNb₂O₅is fully oxidized),

- No loss of sample weight, and

- The sample did not change in color or structure.

 

Conclusions:

In a differential scanning calorimetry test according to Regulation EC No. 440/2008 Method A.1. and OECD test guideline 102 (1995) the test item magnesium diniobate did not melt up to 650 °C.

Description of key information

In a differential scanning calorimetry test according to Regulation EC No. 440/2008 Method A.1. and OECD test guideline 102 (1995), magnesium diniobate did not melt up to 650 °C.