Does passive voice always involve a form of "to be" and a past participle?

Typically, passive voice is defined as using some form of the verb "to be" followed by a past participle form of a verb. For example, "I was saved, "he will be attacked," or "they have not been found."

However,I have been told in the past that some sentences that do not follow this structure are still in the passive voice. For example, "he seemed dismayed," or "that is nothing to be afraid of." Are these sentences or other similar sentences passive?

Can a sentence use a passive voice without following the "to be" + past participle structure? Or is that the only form of passive of voice?

Solution 1:

Wikipedia on the English passive voice says essential components are: a form of the auxiliary verb be (or sometimes get) and the past participle of the main verb denoting the action.

Their examples with get are:

"The window got broken."
"Don't get killed."

Thus these are not passive:

"He seemed dismayed."
"That is nothing to be afraid of."