Does threatening one's wife with divorce by saying, "If you are late again in the evening outside, then I will speak of divorce," constitute a conditional divorce that necessitates expiation, given that the intention was to intimidate and not to utter a divorce?

Your statement: "I will speak about divorce" is neither a divorce nor a suspension of it. Rather, it is merely a promise that does not require expiation. It is advisable to avoid threatening with divorce. When disloyalty (nushuz) appears, the husband should pursue the religiously prescribed means of reform, including admonition, abstention, and non-violent striking.