2641
However , after annealing the original NM structure with a = b = 5.47 Å and c = 6.66 Å with a c/a -ratio of 1.22 was recovered and crystallographic twins could be observed in an SEM .
 annealing, structure, b, c, be, SEM
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 annealing, structure, b, c, be, SEM