How to optimize mysql fulltext union search?

I am making a mysql fulltext search.

my database table article1 has ~18000 articles, article2 has ~7000 articles, article3 has ~13000 articles. FIELD cat is a INDEX field

Now I want to make a union search. there are 5 groups words put into 3 table, match out the results. But the process time is 3.1213495136 seconds. (I add microtime() to see how much time it will cost). Is there any way to optimize mysql fulltext union search? Thanks.

(SELECT title,content,date FROM article1 WHERE 
(cat='novel' AND MATCH (title,content) AGAINST ('+Mary +Barnard' IN BOOLEAN MODE)) 
OR 
(cat='novel' AND MATCH (title,content) AGAINST ('+Patricia +Beer' IN BOOLEAN MODE)) 
OR 
(cat='novel' AND MATCH (title,content) AGAINST ('+Aphra +Behn' IN BOOLEAN MODE)) 
OR 
(cat='novel' AND MATCH (title,content) AGAINST ('+Judy +Blume' IN BOOLEAN MODE)) 
OR 
(cat='novel' AND MATCH (title,content) AGAINST ('+Elizabeth +Bowen' IN BOOLEAN MODE)))
UNION 
(SELECT title,content,date FROM article2 WHERE 
(MATCH (title,content) AGAINST ('+Mary +Barnard' IN BOOLEAN MODE)) 
OR 
(MATCH (title,content) AGAINST ('+Patricia +Beer' IN BOOLEAN MODE)) 
OR 
(MATCH (title,content) AGAINST ('+Aphra +Behn' IN BOOLEAN MODE)) 
OR 
(MATCH (title,content) AGAINST ('+Judy +Blume' IN BOOLEAN MODE)) 
OR 
(MATCH (title,content)AGAINST ('+Elizabeth +Bowen' IN BOOLEAN MODE)))
UNION 
(SELECT title,content,date FROM article3 WHERE 
(MATCH (title,content) AGAINST ('+Mary +Barnard' IN BOOLEAN MODE)) 
OR 
(MATCH (title,content) AGAINST ('+Patricia +Beer' IN BOOLEAN MODE)) 
OR 
(MATCH (title,content) AGAINST ('+Aphra +Behn' IN BOOLEAN MODE)) 
OR 
(MATCH (title,content) AGAINST ('+Judy +Blume' IN BOOLEAN MODE)) 
OR 
(MATCH (title,content)AGAINST ('+Elizabeth +Bowen' IN BOOLEAN MODE)))
Order By date DESC LIMIT 10

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sorry, post in a wrong position. can admin help me move to php? Thanks.