Specifically, only transitive verbs can be used in passive verbs. As passive sentences require a direct object, undergoer or patient to receive an action and show the salient effect, intransitive verbs, which are not used with direct objects, are not compatible with passive sentences. Without a direct object or an undergoer or a patient, the changes/results caused by the actions are not expressed nor shown. What's more, verbs used in the passive sentences cannot be stative too. The reason for the unacceptable use of stative verbs is that stative verbs do not specify an endpoint which is required in a passive sentence. Stative verbs like think are not used in passive sentences, as they carry no end point meaning which cause the event can not be framed as a resulting state in the passive voice.
The reason accounts for the acceptable use of adjectives in a passive sentence is: As adjectives are used to describe nouns or pronouns, they can signify the result of a change. However, as the actions in the adjective-passive sentences aren’t expressed explicitly, adjective-passive sentences tend to pay more emphasis on the before-and-after comparison. Take “she is educated” as an example, “educated” is an adjective describing the subject has learnt a lot from education organizations and is knowledgeable. There are no transitive verbs in the sentence but it is still considered as a passive sentence with the passive marker “be” (is). In this example, the adjective “educated” implies the meaning that the subject “she” is the undergoer of an action, “being taught in school”. And now the undergoer “she” changes from having little knowledge to being knowledgeable.
As aforementioned, the subject actually received an action, “being taught in school”. Thus, a typical passive sentence could be written as “She is taught by her teachers”. In this typical sentence, the doer is shown and the effect on the subject is expressed explicitly. The subject “she” receives education from her teachers who give her knowledge. Unlike the adjective-passive sentence, the typical be-verb passive sentences emphasize the action received by the subject from the doer which sometimes could be omitted. Therefore, this example illustrates the difference between a typical be-verb passive sentence and an adjective-passive sentence. They aren’t the same as they place different emphasis.
Aside that, we actually used adjectives in passive voice as expressions to show our emotion and feelings frequently, for instance, “I am bored.”, “she is worried about her parents’ health.” However, these expressions can not be re-written as “Bored is by me” and “Her parents’ health is worried by her.” These passive adjectives can only be used after a person to express his/her feelings but not used by an object which has no emotions or feelings. What is more, adjectives used in passive sentences carry an -ed suffix which allows the adjectives change from active to a passive state to express one’s idea of an event or an experience. Take “I am bored” as an example, the subject is the one who undergoes an experience and feels bored about that.
Therefore, similar with the typical be-verb passive sentences, adjective-passive sentences demote the agent and promote the non-agent. However, the non-agent in adjective-passive sentences could only be a human but not an object.