Help in analysing dilatometer results

I need some help in analysing results for a dilotometer experiment. I did this experiment for the first time and don't have any prior experience in this field. The main aim of this experiment was calculating the CTE( coefficent of thermal expansion). The type of dilatometer was a push rod dilatometer.


The sample was basic gamma alumina pellet of 19 mm by 3 mm. The pellet was a green body i.e it wasn't sintered. I have attached the resultant graph.


My main doubt is as follows -


1. The operating temperature was at 900 deg cel. For calculating the CTE or linear CTE in this case, do I consider only the intial length at 25 deg cel and final length at 900 deg cel, or do I take into account the up and down trends occuring in between.
2. I am fairly certain that at 900 deg cel the gamma alumina gets converted into another phase, how do I account for the phase changes?
[![Dilatometer result](https://i.stack.imgur.com/Shoq1.jpg)](https://i.stack.imgur.com/Shoq1.jpg)


If anyone could guide me in how to analyse the graph, it would help me a lot. Sorry if this sounds like a basic question, I know homework questions aren't entertained here. This experiment is part of my QA/QC establishing process of my catalyst samples.


