Does the divorce of a man who swore an oath of divorce to his family, while fully in possession of his mental faculties, and who did not inform his wife of this, and intended to take her back as his wife after her return to his home, take effect?

If your statement to your wife was merely a promise of divorce, then no divorce has occurred, and you are obligated to offer expiation for breaking an oath if you do not divorce her. If you do divorce her, you have fulfilled your oath, and there is nothing upon you, and you may take her back. We advise you to keep your wife, for the Prophet, peace and blessings be upon him, said: "Whoever swears an oath and then sees something better than it, let him do that which is better and expiate for his oath." However, if you have actually divorced her, then the divorce has occurred, and you may take her back as long as she is still within her waiting period, with the intention (of reconciliation).