Using a smaller replacement plate in a microwave should generally be safe as long as it fits securely and does not come into contact with the microwave's interior walls or any other metal components. However, it's important to note that the microwave's turntable and plate are designed to ensure even cooking and heat distribution.
Using a smaller plate may result in uneven heating, as the food may not rotate properly or could be positioned closer to the microwave's walls. This can lead to hot spots and potentially undercooked or overheated areas in the food. It's recommended to use a plate that is similar in size to the original one to maintain proper cooking performance.
Regarding microwave radiation, as long as the replacement plate is made of microwave-safe material (usually glass or ceramic), it should not cause any leakage or pose a safety risk. Microwave-safe materials are designed to withstand the microwave's energy without absorbing or releasing harmful radiation.
However, to ensure safety, it's always a good idea to follow the manufacturer's guidelines and recommendations for your specific microwave model. If you have concerns or are unsure, it's best to consult the microwave's user manual or contact the manufacturer for advice on using a replacement plate that is smaller than the original.