Examiners look for "less common lexical items" and "collocation." Using OPAL phrases moves you from a Band 6 (adequate) to a Band 7+ (sophisticated) in IELTS Writing and Speaking.
By consulting the "Results" or "Reporting" section of the lexicon, a student moves from a basic statement to an academic assertion. oxford phrasal academic lexicon pdf
Tell me your goal and I can pull the most relevant phrases for you. Examiners look for "less common lexical items" and