Can someone use contents of expired domains (website’s pages) for a new site? Will it be treated as duplicate content?
Please share your thoughts.
Unless you own the content… the answer is no. Just because a website expires or the domain expires does not mean the copyright expires. All content is owned by the people who wrote it and whether it’s still available online or not is irrelevant. If you use someone else’s content without permission it will constitute copyright theft and you could suffer severe legal consequences for lifting it. 
I think these pages are already indexed and it will be considered as double content. It will be better if you write a new content.
Personally I wouldn’t do it, if it’s not your own content don’t use it.
I don’t find this idea useful because domain expire doesn’t affects the cached data in the google (i think so).
Unless it was your site, it is still copyrite infringment.
If it was your site, see if you can get google to try and spider the old URL and maybe if they can’t find it they will remove the content from their database.
Don’t know if that will work, but it could be worth a try.
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Why are you copying? What if do some researches do new content. For me as a writer, it was sad to me that someone is copying my content without my approval. Do you know that plagiarism is pirating and stealing. Be aware of your conscience.
I respect your feeling Dylan, Believe me I will never do so without prior permissions, I never want to be a thief:nono: